CALIFORNIA STATE UNIVERSITY, NORTHRIDGE
EFFECTIVENESS OF WARNING SIGNS
ON CONSUMER PRODUCTS
A thesis submitted in partial satisfaction of the
requirements for the degree of Master of Arts in
Psychology
by
Shirley Mitsue Otsubo
January, 1988
The Thesis of Shirley Mitsue Otsubo is approved:
California State University, Northridge
ii
Acknowledgement
To all my friends at CSUN (you know who you are). I made it!
To my parents and my sister Peggy, who constantly gave me moral support.
To Tyler Blake, who I thank for introducing me to the field of Human Factors.
To Bill Wilsoncroft, who I greatly thank for helping me through this at the last
minute.
To Norman Schwalm, who encouraged me to finish what I started.
To Gary Nunes-- I wouldn't have made it without him, and
To Mark Sanders, who I can't thank enough for the support and guidance
throughout my years at CSUN.
iii
Table of Contents
~
Acknowledgement
iii
Table of Contents
iv
List of Tables
vii
List of Figures
viii
Abstract
ix
Introduction
Conspicuity
Willingness to Read
Comprehension
Recall
Compliance
User Perceptions
Statement of the Problem
1
3
4
5
7
10
13
Method
Independent Variables
Product Hazardousness
Jigsaw
Circular Saw
Warning Sign Design
Words Only
Pictograph Only
Pictograph + Words
No Warning
Dependent Variables
Subjects
Materials and Setting
Experimental Design
Procedure
16
16
16
16
16
17
17
22
22
23
23
24
24
24
25
9
iv
~
~
Results
Control Subjects
Product Perception
Perceived Hazardousness Score
Product Perception and Prior Use
Perceptions on Type of Warning Sign
Additional Differences Affecting Dependent Measures
Conspicuity
Willingness to Read
Compliance
Recall Danger
Recall Cause
Recall Avoidance
Differences between Sex
Product Hazardousness
Warning Sign Design
Interactions between Independent Variables
Recall Data
Confidence Ratings
Overall Analyses
Additional Response Data
Confidence of Location
Recall of Color and Design of Warning Sign
Comments on Noticing, Reading and Complying
with Warning
Prior Use of Protective Clothing
Experimental Realism
29
30
30
30
31
33
34
34
35
35
37
37
37
38
39
44
48
50
50
50
52
52
54
54
55
55
Discussion
Product Hazardousness
Design of Warning Signs
Familiarity and Experience
Confidence of Product Use
Prior Injury
Other Considerations
Conclusion
56
56
57
61
62
63
64
65
References
68
v
.
,,
Appendix A-
Preliminary Experiment on
Product Hazardousness
Appendix B-
Preliminary Experiment on Warning Sign
Comprehension of the Pictorial Warning Sign
76
Preliminary Experiment- Behavioral
Task Scenario
79
Determination of Letter Height Recommended
for Labels and Marketings on Panels
88
Appendix E-
Instructions to Subjects
89
Appendix F-
Subject Interview and Questionnaire Form
91
Appendix C-
Appendix D -
72
Appendix G - Experimental Data
101
Appendix H -
103
lntercorrelation Matrix of Product Perceptions
vi
'
List of Tables
~
Table
1
Matrix of Experimental Design
26
vii
List of Figures
Figure
~
1
Warning signs
18
2
Subjects who noticed, read and heeded warning
based on product hazardousness
40
Product hazardousness differences contingent
upon prior behavior
42
Subjects who recalled warning message based on
product hazardousness
43
Subjects who noticed, read and heeded warning
based on warning sign
45
Warning sign differences contingent upon prior
behavior
46
Subjects who recalled warning message based on
type of warning sign
47
Data plots of overall percentage of subjects based on
dependent variables
49
Overall percentage of subjects who noticed, read and
heeded warning
51
Overall percentage of subjects who recalled the
warning message of Danger, Cause and Avoidance
53
Sample Questionnaire utilized in Preliminary
Experiment to ascertain differences in
Perceived Hazardousness
74
Pictographic warning sign tested for comprehension
78
3
4
5
6
7
8
9
10
11
12
viii
Figure
13
14
Preliminary Experiment-Behavioral task scenario
Sample Questionnaire
84
Diagram of hinges to be attached to wood pieces
(Part of Subject Instructions)
90
ix
ABSTRACT
EFFECTIVENESS OF WARNING SIGNS
ON CONSUMER PRODUCTS
by
Shirley Mitsue Otsubo
Masters of Arts in Psychology
This study focused on the effectiveness of warning signs (words,
pictographs, and both words and pictographs) placed on products different
in perceived hazardousness. Effectiveness was investigated by studying
the behavior of those who noticed, read, complied and recalled the warning
message. Overall results showed that subjects noticed, read and complied
with warnings placed on products perceived to be more hazardous than on
products perceived to be less hazardous. Additional data suggest that
people less familiar with use of the product will tend to read, comply and
recall the warning more than those who are familiar with the product. Also
people less confident will tend to read and comply with the warning more
than those who are confident with use of the product. A 2x4 betweensubject design was performed, incorporating two levels of product
hazardousness (circular saw=high level of hazard; jigsaw=low level of
hazard) and four levels of warning sign (words only, pictograph only, words
+ pictograph, and no warning). The findings support the contention that the
use of conspicuously designed and placed warning signs on products
influence people to behave cautiously; overall 25.5% complied with the
warning, with the highest compliance (50%) under the condition of high
hazard (circular saw) with use of the warning with words+ pictograph.
X
Introduction
The use of warning signs and labels on consumer products are
common in today's consumer market. We see them on ladders, household
products, typewriters, and even stationery glues. The number of products
with warning signs and labels seems almost endless, and yet there is very
limited data to support their effectiveness.
There are two primary reasons why warnings have become a widely
accepted practice. The first appears to be due to intuitive reasoning.
People believe intuitively that warnings would reduce injuries (McCarthy,
Robinson, & Finnegan, 1982; McGuiness, 1977). The other reason is
based on legal obligations placed upon product manufacturers. Product
manufacturers are mandated by law to provide warnings about immediate
and potential hazards associated with the use of their products.
Many product liability cases have thus been filed, claiming that some
manufacturers have failed to warn consumers about immediate and
potential hazards. McCormick and Sanders (1982) cited one report
sponsored by the Interagency Task Force on Products Liability (1977). This
report found that out of the total number of product liability cases filed, 35%
involved manufacturing defects, 37% involved design defects, and 18%
involved warning defects (p. 501 ). There is also an increasing number of
these cases every year, and human factor experts have been solicited to
aid both in the design of safer products and in the courtroom to serve as
expert witnesses.
With an increase in awareness about warning hazards, guidelines
and recommendations have been written on the effective use of warning
signs. However, little empirical evidence supports these recommendations
(Ross, 1981; Dorris & Purswell, 1978; Peters, 1983; Peters, 1984; McCarthy
et al. 1982).
1
2
Many product manufacturers simply follow these guidelines with the
expectations that consumers will heed the warnings placed on the product.
However, many factors determine the overall effectiveness of a warning.
This effectiveness is dependent upon a successful completion of the
behavioral process which includes:
1.
Detecting the warning;
2.
Reading the warning;
3.
Comprehending the warning; and
4.
Complying with the warning;
Unfortunately, much of the literature on warning effectiveness has
concentrated on Steps 1 and 3 of the behavioral process. Very little
warning research has investigated the propensity to read warnings,
compliance of warnings and recall of warnings: There is also a lack of
behavioral research involving observations of people actually using
products. Instead, most warning research data have been gathered
through surveys and questionnaires (Cochran, Riley & Douglas, 1981;
Wright, Creighton & Threlfall, 1982; Godfrey, Allender, Laughery & Smith,
1983; Dorris & Tabrizi, 1978; Godfrey & Laughery, 1984). The validity of
surveys and questionnaire data can be questioned until validated by
behavioral observations of user-product interactions.
Much of the literature dealing with warnings can be categorized into
three areas of study. One area focuses on the effects of the design of
warnings on warning effectiveness. Another area focuses on how
perceptions of the user influence warning effectiveness. The third area
focuses on the influence of experience and knowledge on warning
effectiveness.
The current study will focus on the effects of specific aspects of
warning design and user perceptions on warning effectiveness. This will be
done by observing users' behavior with products. The effects of words and
@
•
3
graphics and of inherent hazardousness of products on warning
effectiveness will be investigated. Additional data will also be collected to
ascertain whether experience and familiarity of product use influence
warning effectiveness.
The following sections describe results of studies that have
investigated warning sign effectiveness and usage, specifically, studies
pertaining to words and graphics. This review will be presented in terms of
criteria that have been used to determine warning effectiveness. These
criteria include: conspicuity, willingness to read, comprehension, recall and
compliance of warning signs. A review of the literature regarding the
influence of users' perceptions on warning effectiveness will also be
presented.
Conspicuity
To be conspicuous, a warning sign must be detected in a short time,
without active search, because it must be noticed and seen in order to be
effective. Conspicuity may be effected by color, contrast, brightness, size,
and location.
Contrast in the form of highlighting has been investigated (Ziotnik,
1982; Strawbridge, 1986). Zlotnik found no effects of highlighting a signal
word within procedural instructions. Strawbridge also found no difference
in conspicuity attributable to highlighting, imbedding or positioning of the
warning when placed within a product information label, even though a
difference due to highlighting was found between the number of people
who read and did not read the warning.
Conspicuity has also been measured by warning placement. Zlotnik
(1982), and Wogalter, Fontanelle and Laughery (1985), found that placing
the warning message before the instructions was superior to placing it
within the instructions. However, Strawbridge (1986) found no effects of
4
warning position on conspicuity. Easterby, Hakiel, and Graydon (1980)
also found that placing a warning on the upper right corner of a package
aided conspicuity of the warning.
Willingness to Read
The next important step in the behavioral process of complying with a
warning is to read the warning; it must be read before it can be understood.
Readability of words on labels is optimized when the words are presented
in capital letters. Boldfaced letters used in print or typed text were also
shown to be easier to read and recall than regular typed letters or capital
letters (McCormick and Sanders, 1982). However, very little research
evidence exists specifically relating to factors that determine warning sign
readability.
Recommendations and suggestions on warning si'gn readability have
also centered on the use of pictographs and graphics to symbolize warning
hazards (Peters, 1983; FMC, Corp., 1985).
Research on the readability of signs has been conducted in the area
of traffic signage with a focus on symbols and words. Many of these studies
utilized reaction time to ascertain differences in recognition and readability,
based on the assumption that signs that are recognized and read faster will
be more valuable and effective for the driving task. This assumption can
also be directly related to the application of warning signs on products.
It is
reasonable to assume that a warning sign recognized and read accurately
and quickly will be better than other signs that are not read and recognized
as fast.
Unfortunately, the results from these studies are mixed. For instance,
King (1975) found that when subjects were exposed to brief presentations
of both symbol and word traffic signs (1/3 second and 1/8 second), symbol
signs were more accurately recognized under the shorter exposure time
5
(1 /8 second). Walker, Nicolay and Stearns (1965) also used short
exposure time to test differences between American word signs and their
international symbol counterparts. Inspection of the data revealed
that the international signs were correctly identified more often than the
American word signs.
Other studies exhibited contradictory results. Dewar, Ells and Mundy
(1976) studied readability of traffic signs based on reaction time. They
studied verbal and symbolic traffic signs, and found that during a secondary
attention-demanding task, verbal signs were read faster than symbolic
signs. Standing (1973) also found similar results with the use of normal
words and pictures.
Results from these studies may indicate that readability of the signs is
dependent upon specific detailed characteristics of the pictographs and/or
words themselves.
Comprehension
People may be able to read all the words of a sign, but they may not
understand its full message, thus comprehension becomes an important
issue. The major suggestion made to ensure comprehension on labels and
signs is to keep the message simple (Peters, 1983). Other suggestions
include using brief and concise words, and using symbols that are easily
understandable and experimentally validated for comprehension (Eastman
Kodak, 1983).
A group of studies has focused on the comprehension of pictorially
represented signs. A study sponsored by the National Institute of
Occupational Safety and Health (Collins, Lerner & Pierman, 1982)
investigated the comprehension and preference of 33 key safety pictorial
messages gathered from warning sign designers. A total of 87 signs were
gathered. Subjects provided a definition for each sign and then indicated
6
which pictograph best represented a given message. The study found that
the pictographs that included a person and the hazard, action or piece of
equipment appeared to be best understood. A few symbols widely used for
some years were also found to be difficult to understand. In some cases,
less than 25% of the subjects correctly recognized these signs. These
results showed that use over a long period did not always lead to good
comprehension. The overall conclusions of this study indicated that symbol
performance should be evaluated in terms of understandability before
adoption.
Other studies on comprehension of pictographic signs have also been
conducted (Easterby & Hakiel, 1981; Zwaga & Boersema, 1983; Cahill,
1973). Their results indicated that comprehension of the signs were not
markedly high, but with experience and prior exposure to the signs,
comprehension increased significantly.
Ells and Dewar (1979) studied the comprehension of verbal and
symbolic traffic sign messages through reaction time. Their results
indicated that symbolic signs were understood more quickly than verbal
signs. Of course, the results were confounded by the fact that the
experimenters asked subjects if the sign matched a given message, so the
subjects were cued to the possible answer.
Comprehension of both pictographs and words used in combination
was also found to be effective in procedural instructions (Booher, 1975).
The instructional formats combined pictures with print in various ways, in
addition to using formats presented in print alone and pictures alone.
Performance was based on error rate and on time required to complete the
task. The results showed that the most efficient understanding of the
procedural instructions occurred when the pictures were used as the
primary information channel and the supporting text as the secondary
supporting channel to clarify the pictures. Performance using the pictorial
7
format alone was not found to differ from the performance of the
high-pictorial-with-print format. Performance using the print only format was
found to be accurate, but the task took significantly longer to complete than
with any of the other formats.
Based on results from these studies on comprehension of signs, it can
be reasonably concluded that pictorial signs are not always easy to
understand. When subjects had prior experience with the signs,
comprehension improved, but in some cases long-term use did not facilitate
comprehension (Collins et al. 1982). In those cases where pictorial signs
were familiar or easily comprehended by subjects, performance was
significantly better with pictorial format than with words, and the composite
of pictures plus words produced the best performance (Ells et al. 1979;
Booher, 1975).
Recall
To be effective, the information communicated in the warning should
also be remembered and recalled. Very little literature dealing with
warnings has focused on criteria that effect recall of warnings. A study
conducted by
Rothstein(J98~)
found that message length, format, and
pre-questioning affected recall of the warning hazard. Another study
investigated recall of warnings based on historical use of the product and
found that subjects were more likely to notice a warning the first time they
used a product than later. Thus, the more familiar they were with the
product the less likely they would notice and accurately recall the warning
hazard (Godfrey et al. 1984). Zlotnik (1982) studied the effects of
highlighting of warnings on recall and found that few subjects could recall
more than half the warnings, and no one recalled the entire set correctly.
8
(1
Imbedding critical information also impaired recall of cause and prevention
of the injury (Strawbridge, 1986).
Peters (1984) suggested that pictographs serve another purpose
besides being interpretable by those who cannot read English. The
inherent nature of pictures may compensate those who may forget or
become too accustomed to a hazard, and serve as "instant reminders" of
the hazard (p.76). Theoretical data on perception and memory for pictures
support Peters' contentions.
Research studies have found that people recognize and recall
pictures far better than words. For instance, Paivio, Rogers and Smythe
(1968) found the colored sets of pictures were recalled significantly better
than their colored noun labels (i.e. picture of a red apple versus the
word-label "apple" colored red). Sampson (1970) also found that subjects
were able to recall pictures better than words immediately after the study
test, and even one day later. Another research study conducted by
Standing, Conezio and Haber (1970) presented approximately 2,000
photographs to subjects (each photograph presented every 10 seconds).
Some subjects viewed the stimuli over a period of two days and others over
a period of four days. After all stimuli were presented, subjects were given
a test, consisting of a pair of pictures, one selected from those shown and
the other from those not shown. Subjects chose which picture was shown
in the original set. Subjects, on the average, responded correctly 85-95%
of the time. Another study compared recognition and recall of both pictorial
material and verbal material (Standing, 1973). Subjects were shown a set
of stimuli consisting of pictures and words. Two days later, subjects
performed a recognition test. These results showed that pictures were
identified correctly more often than words. Standing also conducted
another study in which various stimuli consisting of pictures, words, auditory
words, and nonsense syllables or music segments were presented.
•
9
il
Subjects were instructed to attend to the stimuli, and after the stimuli were
presented, subjects wrote down as many items as they could recall. Results
indicated that pictures were not only recognized better but were also
recalled better than words, whether the words were presented visually or
auditorially spoken. Words were also recalled and recognized better than
nonsense syllables.
Results such as these indicate that people recognize and recall
pictures far better than words. If this concept is applied to warning sign
usage, pictographs may indeed act as "instant reminders" to those who may
have forgotten about the hazard. It must be noted that in these perceptual
experiments, subjects were motivated to remember the stimuli by simply
being told to remember as many pictures as possible for future recall. If
they were placed in a situation where motivation to attend to the stimuli was
not present, there may be some question as to whether there would still be
a wide difference in recall between words and pictures.
Compliance
Most important to warning sign effectiveness is its facility to encourage
compliance. That a warning is noticed, read and understood, does not
necessarily assure that the warning will be heeded. Most of the evidence
on warning compliance has been gathered through behavioral research
studies, observing subjects using the product. Much of this research,
although limited, has found that warnings influence behavior, but not
necessarily to the extent expected.
When warnings were placed within instructions for a procedural task,
error rates were reduced and task performance time decreased (Ziotnik,
1982). Wogalter et al. (1985) also studied warnings placed in instructions,
and found that compliance increased with the use of the warning, and
.
10
greatest compliance occurred when the warning was placed before the
instructions (86-90% compliance).
Warnings were also found to be effective in "real world" settings
(Godfrey, Rothstein & Laughery, 1985). After a few iterations in warning
sign design were made to improve on the signs, it was found that when
these improved warning signs were placed on a copy machine, a public
telephone, a water fountain and two sets of doors, most people complied
with the warnings (66-1 00% compliance) .
.J;;.
On-product warnings have exhibited mixed results. Strawbridge
(1986) tested various forms of highlighting, position and imbedding of
warnings on product labels. The significant finding indicated that subjects
were less likely to comply when the critical warning information was
imbedded within the product label. However, when the overall number of
subjects' responses were analyzed, it was found that only 37% complied
with the warning. Moreover, a study conducted by Dorris and Purswell
(1977) placed one of three warnings on hammers. Subjects were then
requested to use the hammers. Two of the warnings directed the subjects
to stop performing the task, but out of 100 subjects, no one even noticed the
labels.
The overall results of these studies on compliance indicate that
warnings do influence behavior but not always at the high level of
compliance expected. Thus, the need for additional studies on warning
compliance is apparent.
User Perceptions
Another area of research on warnings has focused on users'
perceptions of consumer products and of warning signs themselves. Much
of the data on the effect of users' perceptions on warnings have been
gathered through surveys and questionnaires (Godfrey et al. 1983; Godfrey
11
et al. 1984; Cochran et al. 1981; Wright et al. 1982; McGuinnes, 1977;
Dorris & Tabrizi, 1978; Bresnahan & Bryk, 1975).
One group of studies on warning signs indicates that warning sign
characteristics of shape, color and the use of "signal words" denote certain
perceived degrees of hazard. Cochran et al. (1981) examined 19
geometric shapes of warning labels. Through paired comparison, subjects
selected the preferred shape for warnings. The findings indicated that the
triangle on its vertex was the preferred choice. The possible explanation for
this result is that the triangle on its vertex is very similar to the shape of
traffic "yield" signs. Other shapes similar to traffic signs were also rated
highly. These results indicate that familiarity and prior experience with
signs influenced subjects' response.
Another research study conducted by Bresnahan and Bryk (1975)
found that different colors and signal words were associated with different
degrees of hazard. In fact red and yellow, which were associated with the
signal words "DANGER" and "CAUTION" exhibited a higher degree of
hazard than green or blue, which were associated with the signal words
"SAFETY INSTRUCTION" or "INSTRUCTIONAL."
Another group of surveys investigated user perceptions of products
and warnings. One such survey asked users to rate products on
skin-contact hazard, inhalation hazard, swallowing hazard and overall
hazard (Godfrey et al. 1983). They were also asked how familiar they were
with the products, and if they would read a warning if placed on the product.
The results indicated the more hazardous subjects perceived a product, the
more likely they said they would look for a warning. Also familiarity and sex
influenced users' tendencies to look for a warning. If the subject was male
and familiar with the product, there was less likelihood that he would look
12
for a warning. Godfrey et al. (1984) also found that subjects said they were
less likely to notice a warning when they were familiar with a product.
Additional factors influencing people's willingness to read instructions
were also investigated (Wright et al. 1982). Subjects were presented a list
of products and asked to indicate how much of the instructions they would
read for each product. Subjects also rated each product on familiarity,
safety, simplicity of operation, cheapness and frequency of use. Findings
indicated that instructions were more likely read with products that were
perceived to be complex to operate. Instructions of those products that
were frequently used were also less likely to be read.
Dorris and Tabrizi (1978) surveyed subjects' perceived hazard rating
of products with actual injury data collected from the Consumer Product
Safety Commission. Their results did not reveal a correlation between the
perceived hazard and actual injury data. In fact, some products were
perceived less hazardous and some products were perceived to be more
hazardous than the injury data suggested they really were. The
experimenters did make an interesting note that the products, which had
blades or cutting surfaces, and thus were associated with the "potential
hazard of being cut" were perceived to be more hazardous than the injury
data indicated. A simple explanation may be, if people were more cautious
using such products, it can be assumed that fewer injuries would result.
McGuinness (1977) also surveyed preference for a sign relating to the
hazard of spinning blades on lawn mowers. Subjects preferred the pictorial
sign that exhibited detailed result of the hazard over other less explicit
signs.
Based on these studies conducted on users' perceptions of products
and warnings, there is evidence that the effects of familiarity, complexity,
frequency of use and hazardousness of the product may influence whether
13
warnings will be noticed and heeded. Unfortunately, no behavioral studies
have been investigated to validate these conclusions.
Statement of the Problem
The current study will focus on two independent variables. The first is
product hazardousness and the other is warning label design based on the
use of words and pictures. These variables will be investigated to
determine their effects on the following dependent measures:
1.
whether subjects notice the warning;
2.
whether subjects read the warning;
3.
whether subjects understand the warning;
4.
whether subjects comply with the warning; and
5.
whether subjects recall the warning.
Subjects have suggested that they would be more likely to look for
warnings if a product was perceived to be hazardous (Godfrey et al. 1983).
This influence of perceived hazardousness may be a critical factor in
determining if IDlY warnings will be heeded-- whether they were placed in
procedural instructions on a product, or on a product package. The current
behavioral study will observe whether subjects do indeed notice, read,
understand, comply and recall a warning placed on a product
perceived to be more hazardous than on another similar product perceived
to be less hazardous.
The concept of perceived risk, or "perceived hazardousness" as
referred to in this study, has been widely used in the field of safety
engineering. This concept has been defined as, " ... probability times the
loss in dollars, lives, or operating units that could occur" (Hammer, 1972; p.
55), with maximal hazard associated with high probability and severity of ·
accidents. This formula has also been referred to as the "Loss Rate
Concept" (Loss Probability x Loss Severity) and has been used to
14
determine whether a system or product is inherently safe, and thus without
risk (Browning, 1980). For instance, risk prediction has been used to
ascertain potential equipment losses, aircraft mishaps, and anticipated
insurance costs.
Applying this formula to the present study, perceived hazardousness
of a product will be operationally defined as the "perceived seriousness of
injury" times the "perceived likelihood of injury" (or "seriousness x
likelihood" of injury).
Pilot studies were conducted to identify the two products that were
used to represent "low" product hazardousness and "high" product
hazardousness (see Appendix A).
The current investigation hypothesized that subjects exposed to the
high product hazard would more likely look for and thus notice the warning.
Subjects may become cautious and careful using the more hazardous
product. Further, if the subjects notice the warning, it was hypothesized that
subjects would continue through the behavioral process of reading,
understanding and complying with the warning.
The other independent variable used in this study was warning sign
designs based on the use of words and pictures. Three types of warning
signs were designed. One design contained a warning only in words, one
with only a pictograph, and the third with the combination of both words and
pictograph.
It was hypothesized that the warning sign with both words and
pictograph would effect the dependent variables of readability,
comprehension, compliance and recall more than the "pictograph only"
sign. The redundancy in the warning message represented in both
pictograph form and words will confirm the hazard message more strongly
than the other message acting alone. Also, since the warning with "words
only" did not exhibit a pictorial representation of the hazard, the perceived
15
level of hazard may seem less than the warning with both pictograph and
words. Thus, the "words only" warning would be read, understood, and
complied with less than the composite sign.
Even though some studies on readability indicate pictographs may be
more readable than words, it was hypothesized that since the warning was
not familiar to any of the subjects, the subjects would not take the time
required to decode and understand its message. Thus, it was hypothesized
that the warning with "words only" would be read, understood, complied
with and recalled more often than the warning with "pictograph only."
Since features that influence conspicuity (size, location, brightness,
color, highlighting) were constant across all warning sign conditions, no
effects of conspicuity were expected.
Q
•
(l
Method
Independent Variables
The effects of two independent variables were investigated in this
study: product hazardousness (low and high) and warning sign design
("words only," "pictograph only," and a combination of both
"pictograph+words").
Product Hazardousness
Perceived hazardousness of a product is operationally defined as the
subjective estimate of "likelihood x seriousness" of injury with use of the
product. Through a preliminary survey, two products were found to be
similar in recency and frequency of use, ease, safety and confidence of use,
but not in respect to their perceived hazardousness or "likelihood x
seriousness" of injury. These products were an electric jigsaw and an
electric circular saw (N=1 00, hazard rating for jigsaw M=18.947; hazard
rating for circular saw .M=24.339) see Appendix A for full details.
From this pilot experiment, the two products were shown to be
significantly different in perceived product hazardousness. Thus, in the
current study they represented the two levels of product hazardousness.
Jigsaw. The jigsaw is encased in a metal housing, manufactured by
Black and Decker, model no. U-153, and the approximate size is 6-1/2"L x
2-1 /2"W x 8"0. The maximum horsepower is 1/7 and it operates at 115
V.A.C., and at 2.4 Amps.
Circular saw. The circular saw is manufactured by Craftsman, model
no. 315.23890. The approximate size is 1O"L x 12"W x 9"0, and uses a
7-1/2 inch diameter blade. The saw operates at 115 V.A.C. and at 11 amps.
16
•
17
Warning Sign Design
Three warning signs were utilized in this study. One warning was
designed with "words only," another warning was designed with "pictograph
only," and the third warning was designed with both "pictograph and
words." Through pilot studies to determine optimal size, design and
location of warnings on the two products, the final set of warning signs was
used (see Appendices Band C for details on pilot studies).
Words only. The warning message of the "words only" sign was
designed to convey four message elements: the level of hazard, the nature
of the hazard, the consequence of the hazard, and the avoidance of the
hazard (see Figure 1). The signal word, "CAUTION" denoted the level of
hazard, "SHARP BLADE" denoted the nature of the hazard, "CAN CUT"
denoted the consequence of the hazard, and "WEAR GLOVES" denoted the
avoidance of the hazard (Wogalter, Desailniers, & Godfrey, 1985(b)).
Wogalter et al. (1985b) found through questionnaire surveys, that warning
signs were perceived as most effective when all statements were used in
combination.
FMC Corp. (1985) also recommends the use of all the warning
statements in their warning sign and label system. The design features
recommended in this system consists of the following: a signal word
(DANGER, WARNING or CAUTION) conveys the level of hazard
seriousness, a pictorial communicates the nature and consequence of the
hazard, and an instruction message instructs how to avoid the hazard.
The signal word, "CAUTION" was chosen because the word identified
potential hazards (ANSI Standard Z35.1-1973; Bresnahan & Bryk, 1975;
FMC, Corp., 1985). In this study the potential hazard was identified as
possible lacerations or cuts. The degree of hazard associated with the
signal word "CAUTION" was rated by subjects and was shown to be greater
18
CAUTION!
~
*SHARP
BLADE
CAN CUT
WEAR
CAUTION!
~
~
CAUTION!
SHARP
BLADE
CAN CUT
WEAR
GLOVES!
GLOVES!
Yellow Background Color
Figure 1.
Warning Signs
19
than the words "SAFETY INSTRUCTION" or "INFORMATIONAL," but less
than the word "DANGER" (Bresnahan & Bryk, 1975). Thus the word
"CAUTION" was chosen in this study to signify the potential hazard of
cutting oneself.
The overall size of the sign was 1-3/8" W x 2-7/8" L. This size was
determined by several factors. The primary factor was the placement of the
warning sign. In evaluating the available areas of the saws, and through
pilot testing (Appendix C), it was determined that the warning signs should
be placed on the handles of the saws.
The physical shape of the handles limited the possibility of using
different shapes of warning sign. The width of the handles are
approximately 1 inch to 1-1/4 inches, thus the width of the warning sign was
designed in consideration of this limitation.
The required size of the alphanumeric characters in the warning
message was another factor in determining the overall size of the warning.
To ensure the warning message was legible, the size of the alphanumeric
characters was determined by a procedure outlined by Peters and Adams
in McCormick and Sanders (1982). This procedure determined the
suggested height of letters based on illumination, viewing distance, viewing
conditions and importance of reading accuracy. The formula used in the
procedure is outlined in Appendix D.
Through pilot tests, the viewing distance for a person 6 feet 3 inches in
height was found to be approximately 28-30 inches. This figure was used
to represent the maximum viewing distance anticipated. The illumination
was anticipated to be above 1.0 footcandles, under favorable reading
conditions, and the warning label was considered an important marking
due to the importance of accurately reading the warning message.
20
Applying the formula (Peters and Adams) to the variables outlined above,
the suggested height of the alphanumeric characters was:
H(height of letter, in)= .0022(30) + .06 + .075
=.201 inches
Grandjean (1985) and Woodson (1981) also offered suggested letter
heights based on viewing distance and luminance. Unfortunately they fall
short by excluding viewing conditions and importance of reading accuracy.
Thus, for this study the letter height recommended by Peters and Adams
was used.
The words on the warning were also displayed in all capital letters.
McCormick and Sanders (1982) cited literature on the readability of printed
text and noted that with continuous text, conventional upper and lower-case
words were read significantly faster than words in all capital letters.
However, when words were placed on labels, the authors state," ... the
shoe is on the other foot; words in all capital letters in this type of situation
generally are more readable than those in lowercase or mixed type" (p.95).
The stroke width-to-height ratio of the alphanumeric characters is also
important in determining legibility. The stroke width-to-height ratio for the
letters used in this study was 3:20, which is between 1:6 and 1 :7.
McCormick and Sanders (1982) suggest, based on experimental evidence,
that stroke width-to-height ratio becomes important under unfavorable
reading conditions. Based on studies they have gathered, the ratio of black
letters on a white background should be 1 :6 to 1 :8. Grandjean (1985) also
suggests a stroke width of 1:6. The stroke width of 3:20 used in the current
study was within this range.
21
McCormick and Sanders (1982) also suggest that the width-height
ratio should be 1 :1, but may be reduced to 3:5 without loss in legibility.
They cite the alphanumeric font specification within the United States
Military Specification No. MIL-M-180128. This set of characters has a
width-height ratio of 1 :1 except for a few identified letters, and have been
tested and found to be satisfactory. Grandjean (1985) also recommends a
width-height ratio of 2:3. In this current study, the width-height ratio was
7:10, which is within the acceptable range.
It was possible that the warning sign would be obscured and hidden
by the hand of the user. To reduce this possibility, the size and color of the
sign were considered. The warning sign covered approximately 50% of the
surface area of the jigsaw handle, and over 30% of the surface area of the
circular saw handle directly visible to the user. To achieve maximal
detection of a sign placed on a package (Easterby et. al, 1980), it was
recommended that the sign occupy 5% of the package's front panel surface
area. Taking into account the unfavorable conditions of placing the warning
sign on the handle of the saw, it was assumed that by increasing the
recommended size from 5% to 30% and 50%, the warning sign would be
conspicuous and detected by those using the saw.
To increase conspicuity, the background color of the warning sign was
yellow. In the event that the sign was not totally observable, sections of the
yellow warning would be visible, and thus might catch the eye of the user.
Besides the added value of color to "catch the eye," the legibility of black
letters on a yellow background is good (Eastman Kodak Co., 1983). There
is evidence that the colors yellow and red are associated with hazard cues,
more than the colors green or blue (Bresnahan & Bryk, 1975), and thus
were considered when designing the warning signs. Two warning design
publications use color to represent hazard levels. The American National
22
Standard Institute's Specification for Accident Prevention Signs
(Z35.1-1973) and FMC Corp.'s (1985) "Product Safety Sign and Label
System," both use the color yellow to denote CAUTION. Thus, in this study,
the background color was yellow to designate the hazard level of
CAUTION.
Pictograph only. The "Pictograph Only" warning was designed to
pictorially represent the same warning message as the "words only" sign.
In the pictograph (see Figure 1), a blade is shown cutting a hand. This
translated to the section of the warning message that read, "SHARP BLADE
CAN CUT." The bottom of the pictograph displays someone putting on a
glove. This translated to the section of the warning message that read,
"WEAR GLOVES." Thus, both warning signs "words only" and "pictograph
only" conveyed the same warning message.
In another pilot study (see Appendix B) confidence ratings of subjects
were gathered to substantiate the comprehension of the "pictograph only"
warning sign. All subjects (1 00%) interpreted the sign correctly by giving
such responses as, "You can cut your hand, so wear gloves," or "Wear
gloves." These results indicated that subjects understood the pictograph
and were fairly confident of their interpretation.
This sign also included the following features. A signal word,
"CAUTION" was used. The size dimensions of the pictograph (15/16"W x
1-1/B"L) was approximately the same size as the warning message in
words (1 "W x 1-1/B"L). Thus, the pictograph will occupy the same amount of
area on the warning sign as the message in words. The overall size of the
sign was 1-3/B"W x 2-7/B"L, similar to the warning sign with "words only,"
and the background color of the warning sign was yellow.
Pictograph +Words. The same warning message in both pictograph
and words as specified above were incorporated into one warning sign.
il
.
23
The placement of the pictograph above the words follow similar guidelines
recommended by FMC, Corp. (1975) which also places the pictograph
above the words. This combination of both pictograph and words on one
warning sign was the final factor in determining the overall size for all signs
(1-3/B"W x 2-7/B"L). The same overall size was used for all warning signs to
maintain control of warning size across all conditions. Other common
features included the same signal word, "CAUTION," and the background
color yellow.
No Warning. One group was not exposed to any warning at all, thus
designated as a control group. It was anticipated that a small percentage of
subjects would put gloves on during the task irrespective of a warning.
Thus, a control group was necessary for comparison against the
experimental groups exposed to the warnings.
Each sign was colored in yellow with a Magic Marker and laminated
with ClearSeal Laminating Film to alleviate the possibility of abrasion and
deterioration with extended use.
Dependent Variables
Seven dependent variables were measured. These variables were:
1. whether the
subject~
the warning;
2. whether the subject Iili!Q the warning;
3. whether the subject recalled the cause of the hazard;
4. whether the subject recalled the conseguence of the hazard;
5. whether the subject recalled the avoidance of the hazard;
6.
how confident they were of the meaning of the warning sign; and
7. whether the subject complied with the warning.
24
Occurrences of the first six variables were gathered through the
post-experimental interview. Occurrences of the seventh variable was
observed during task performance.
Subjects
Subjects from Introductory Psychology classes and other classes
requiring experimental credit from Cal State Northridge participated in the
experiment. A total of 131 subjects participated individually in the
experiment. At least 16 subjects per condition participated in each of the 8
experimental conditions. The total subject pool comprised of half males
and half females.
Materials and Setting
The setting represented a real-world worktable for storing and using
hand tools. Various tools were accessible to the subject, such as
screwdrivers, a hammer, various wrenches and pliers, nails, a measuring
tape, a ruler, and a pencil. Protective equipment were also available, such
as a face mask, eye goggles, and hand gloves. A piece of wood,
approximately 36" long, 12" wide and 1" deep was clamped to the table
stabilized with two C-clamps.
Experimental Design
A 2x4 between-subject experimental design was employed. Two
conditions of perceived product hazard (high and low) and four conditions
of warning sign design ("Words only," "Pictograph only,"
"Pictograph+Words," and no warning) were used.
A minimum of 16 subjects were assigned to each experimental
condition. To anticipate a possible effect due to differences in sex,
25
approximately equal number of males and females were assigned to each
condition. Table 1 represents the matrix of the experimental design and
indicates the number of subjects in each condition. All conditions were not
of equal size, thus to compute proper analysis of variance statistics,
StatView 512+, a commercial Macintosh computer statistics package
distributed by Brainpower was used, which calculated an unweighted
means analysis which assumes that the groups came from the same
population.
Procedure
Subjects were told that they will be expected to use an electric saw. If
they felt uncomfortable with using the saw, they were given the opportunity
to decline participation in the experiment. Six people declined to
participate (5 females, 1 male). For those who continued, they were asked
to imagine that they were at home alone, and wished to repair a small
bookcase. The subjects were directed to the worktable where various tools
were located. A piece of wood was clamped down on the table with two
C-clamps, and the subjects were instructed to repair the bookcase by first
measuring 12 inches off the end of the wood, cutting the wood at that
position, then connecting the two wood pieces together with hinges located
.
on the table. The subjects were told to use any tools and equipment on the
worktable at their convenience, and it was stressed that they perform the
task the way they would normally approach it. (See Appendix E for
instructions given to subjects)
At that point subjects were told to begin. The experimenter was
positioned approximately 10 feet behind the subject to be as unobtrustive
as possible, and subjects' behavior were observed.
A step-by-step record of subjects' actions were recorded, including
whether subjects put on gloves.
26
Product Hazardousness
Warning
Sign
Design
No Warning
Words Only
Pictures Only
Pictures+ Words
Total Number
of Subjects
Table 1.
High
16
16
18
16
66
Low
17
16
16
16
+
Matrix of experimental design
65
=
131 subjects
21
When subjects were observed plugging the tool in the extension cord
and pressing the switch to turn on the power, they were stopped from
continuing with the remainder of the task. The extension cord was hidden
from view and not connected to an electrical outlet, thus preventing the
subject from turning on power to use the tool.
An interview was conducted immediately thereafter to elicit the
subject's perception and recall of the warning message. The subjects were
initially asked whether they noticed a warning. If their response was yes,
they were asked where the sign was located. A confidence rating on a
scale from 1 to 7 (7=very confident) regarding how confident they are that
they knew where the warning was placed was elicited. The subject was
further probed whether they r.e..a.Q and understood the warning. If they did,
the subjects were asked to interpret the message and rate their confidence
level on a scale from 1 to 7 (7 = very confident) how confident they are that
they understood the warning message. The subjects were further asked to
.t:e.Q.illl the specific warning statements: the danger, the cause of the danger
and how the danger could be avoided. These responses on recall were
recorded as incorrect (with a score of "0"), partially correct (with a score of
"1 "), and fully correct (with a score of "2"). To confirm their recall responses,
the subjects were given a sheet of paper to draw the warning sign as
accurately as possible. Comments and explanations for their actions were
recorded.
Additional questions were directed toward perceived attitude and use
of the tool. Responses from these questions were gathered to determine
subjects' level of perceived hazardousness of the situation, additional
differences between the saws that may exist, and other relationships that
may have attributed to warning effectiveness. The subject was also
questioned as to the realism and general perception of the experimental
28
setting and situation to substantiate generalizability and external validity.
See Appendix F for a sample of the questionnaire.
Results
This section presents results of the study in the following manner:
1.
Information regarding subjects' perceptions and prior experience with
the circular saw and jigsaw are presented to substantiate differences in
perceived hazardousness existed between the two electric saws, to
determine other possible differences between the electric saws, and to
provide further insight to why subjects performed as they did in the
experiment.
2. Analysis of the independent variables are presented. These data
include whether subjects noticed, read, complied with and recalled the
warnings based on product hazardousness and type of warning sign.
3.
Recall data and confidence of warning sign were also receded to take
advantage of parametric analyses, and the data are presented.
4. Overall analyses of the dependent variables are presented.
For a complete set of raw data see Appendix G.
All statistical tests were tested at the .05 level, and other results close to
this level are presented as suggested differences. With chi-square
calculations, Phi coefficients are reported (<1>) and with complex chi-square
calculations, contingency coefficients (C) are reported (phi coefficients (-1 to
1) and contingency coefficients (0 to 1) both show degree of relationship). If
any cell size fell under 10, both chi-squares with Yates' correction for
continuity to compensate for the low cell size and chi-squares without
continuity correction are presented.
Data from the control group were not included in the analysis unless
specifically stated.
29
30
Control Subjects
A group of control subjects performed the same task as the
experimental groups except no warning sign was placed on the electric
saw. It was observed whether control subjects would use gloves
irrespective of a warning sign. Thirty-three (33) control subjects performed
the same task (16 using the circular saw and 17 using the jig saw) and
none were observed using gloves.
Product Perception
Perceived Hazardousness Score
To substantiate whether subjects did in fact perceive the two electric
saws to be significantly different in perceived hazardousness, subjects were
asked after the experimental task was completed, to convey how they felt
about the electric saw both before the experiment (before they were able to
handle the saw)
and~
the experiment (after they were able to pick it up
and handle it). Each subject's response from Question 24 ("How did you
feel about how likely an injury may occur before the experiment?") and
Question 25 ("How did you feel about how serious of an injury may occur
before the experiment?") were multiplied together to determine the
"perceived hazardousness score" (Loss Probability x Loss Severity)
(Browning, 1980) applicable to how they felt before handling the saw. A
2-way analysis of variance was conducted to determine main effects or
interaction effects of the independent variables based on the perceived
hazardousness score, and no significant differences were found. Thus
subjects felt no different in perceived hazardousness before the experiment
began. However this result may not have reflected their true perception of
the situation, but may have been influenced by their commitment to
participate in the experiment. Since subjects were given the opportunity to
decline participation and rejected this opportunity, they may have felt that
31
the task and tool were non-threatening, thus before performing the task,
subjects perceived both circular saw and jigsaw to be equally hazardous.
However, as they proceeded to perform the task, their perception
changed. Through comparing the "Perceived Hazardousness Score"
obtained from Question 30 ("How likely is an injury to occur now that you
performed the experiment?") and Question 31 ("How serious of an injury
may occur now that you performed the experiment?") (F(1 ,92)=5.506,
~=.0211
), those who handled the jigsaw perceived it to be less hazardous
(M=8.938) than the circular saw (M=13.48) after given the opportunity to
handle the tool. Thus subjects may have initially felt the saws were equally
safe to use before the experiment began, due to their commitment to
participate in the experiment, but during the experimental task their
perceptions changed, and the difference in hazardousness between the
two saws became apparent. These results substantiate that the products
were perceived as different on levels of hazardousness: the circular saw
was perceived to be more hazardous than the jigsaw.
Product Perception and Prior Use
Questions pertaining to product use and perception scored on a scale
from 1-7 (Questions 19,20, 22-25, 27-32) were compared against the
independent variables using a 2-way analysis of variance. These tests
were conducted to help determine other apparent differences in subjects'
perceptions on the effects of using the tools.
Main effect differences were found between the electric saws on the
following questions:
1. (Question 28) How easy is it to use now that you have performed the
experiment? (E(1 ,92)=6.81,
~=.01
06) Those who handled the jigsaw
(M=2.542) perceived it to be easier to use after they handled the saw than
those who handlced the circular saw (M=3.16).
32
2.
(Question 29) How safe is the product to use now that you have
performed the experiment? (f(1 ,92)=5.333, Jl=.0208) Those who handled
the jigsaw (M=2.5) perceived it to be safer to use after they handled it than
the people who handled the circt:Jiar saw (M=3.08).
3.
(Question 30) How likely is an injury to occur now that you performed
the experiment? (E(1 ,92)=7.095, j2=.0091) Those who handled the jigsaw
(M=2.229) felt less likely to be injured after they handled the tool than those
who handled the circular saw (M=2.94).
4.
(Question 32) How confident are you in using the tool now that you
performed the experiment? (F(1 ,92)=4.701, Jl=.0327) Those who handled
the jigsaw (M=2.333) felt more confident after they handled it than those
who handled the circular saw (M=3.06).
Remaining questions on product use and perception were gathered on
subjects' familiarity (Questions 17 and 18) and subjects' knowledge of prior
injury using tools (Questions 33, 34, 34a). Chi-square tests were performed
to determine differences in the electric saws. The only difference resulted in
Question 34, "Do you know of anyone who was injured using this tool?"
(x 2 (1, N=98)=6.634, Q=.01 with continuity correction, <!>=.287). More
subjects knew others injured using the circular saw than the jigsaw.
Differences were also found to exist for the jigsaw when t-test
comparisons were conducted on questions regarding before and after
handling the saw. Significant differences were found between:
1. (Question 22 and 28) "How did you feel about its ease of use before the
experiment?" and "How easy is it to use now that you have performed the
experiment?" (1 (96)=3.843, Q.=.0003) Subjects felt the jigsaw easier to use
after the experiment (McJiff=.446).
2.
(Question 23 and 29) "How did you feel about how safe it was to use
before the experiment?" and "How safe is the product to use now that you
33
have performed the experiment?" (1 (96)=2.717, Q.=.0085) Subjects felt the
jigsaw was safer to use after the experiment
3.
(~iff=.338).
(Question 24 and 30) "How did you feel about how likely an injury may
occur before the experiment?" and "How likely is an injury to occur now that
you performed the experiment?" (1 (96)=2.006, Q.=.0491) Subjects felt it
less likely to be injured using the jigsaw after the experiment
4.
(~iff=.308).
(Question 27 and 32) "How confident were you in using the tool before
the experiment?" and "How confident are you in using the tool now that you
performed the experiment?" (1 (96)=3.081, Q.=.003) Subjects felt more
confident in using the jigsaw after the experiment
(~iff=.292).
There were no differences on the questions regarding before and after
handling the circular saw.
These results demonstrate that the jigsaw was perceived to be less
hazardous than the circular saw once the subjects had an opportunity to
handle the saw. Subjects also felt less likely to be injured using the jigsaw,
perceived it to be much easier and safer to use than the circular saw, and
were more confident with its use than the circular saw. There was also
marked differences between before and after using the jigsaw. Subjects felt
the jigsaw to be easier, safer, less likely to be injured and more confident
using it after the experiment than before the experiment.
Perceptions on Type of Warning Sign
One main effect difference was found for type of warning sign and
Question 32, "How confidence are you in using the tool now that you
performed the experiment?" (E(2,92)=3.546, Q.=.0328) This result showed
that type of warning sign affects the confidence level of the subject after
using the tool. Tukey's test to find significant differences between groups
was conducted and a significant difference was found between "words only"
34
and "pictograph+words" ( C.diff.-1.006, N=32, Q<.05). People were
significantly more confident with the warning sign with "words only" (M=222)
than with "pictograph+words," (M=3.219) but no differences were found to
exist between the warning sign with "pictograph only," (M=2.765) and the
other warning sign conditions.
Additional Differences Affecting Dependent Measures
To assess relationships between subjects' perceptions and the
dependent measures, t-tests comparisons and chi-squares were performed
on questions pertaining to product use and perception, and the dependent
measures. The following significant differences were found:
Conspicuity
Using at-test comparison, a significant difference was found between
those who noticed and those who did not notice the warning and their
perception of how likely an injury would occur after they handled the tool
(Question 30) (1 (96)=2.035, Q=.0446). Those who noticed the warning felt
that it is more likely that an injury would occur (M=2. 794) than those who did
not notice the warning (M=2.229). A suspected difference is also apparent
(1 (96)=1.884, Q=.0626) on their perceived hazardousness score (likelihood
x seriousness of injury) after they handled the tool. The perceived
hazardousness score is higher for those who noticed the warning
(M=12.587) than those who did not notice the warning (M=8.857).
These results indicate that the difference in perceived hazardousness
inherent in the electric saws affects whether one will notice warnings. No
other differences between the electric saws were attributed to differences in
conspicuity.
35
Willingness to Read
A simple chi-square test suggests a significant relationship between
familiarity and prior use of a similar tool (Question 18) (x 2 (1, N=63)=3.835,
.Q=.0502 with continuity correction (or 2=4.91, .Q=.0267 without continuity
x
correction), <1>=.279). Those who had used a similar tool were less likely to
read the warning than those who had not previously used a similar tool.
Recency in tool use (Question 19) also was found to be significantly
related to the willingness to read a warning based on at-test comparison ( 1
(30)=2.113, .Q=.043). Subjects who more recently used the tool (M=4.667)
were less likely to read the warning than those who used the tool less
recently (M=3.294). Frequency of use also exhibited a suspected difference
(Question 20) (1 (30)=1.922, .Q=.0641 ); those who use the tool frequently
(M=4. 733) were less likely to read the warning than those who use the tool
less frequently (M=3.471 ).
Difference in confidence of use (before handling it) was also found to
relate to whether one would read a warning (1 (61 )=2.313, .Q=.0241 ). The
more confident they were (M=3.474), the less likely they would read the
warning than those less confident (M=2.36).
These results suggest that familiarity with the tool may be critical in
determining whether one will read a warning. That is, if one has used a
similar tool recently, and frequently, it is less likely that the person will read
a warning. Confidence in use of the tool also appears important. If a
person is more confident before using the product, than it is less likely the
person will read a warning.
Compliance
A significant difference using at-test comparison was found between
confidence before using the tool (1 (40)=2.038, .Q=.0485) and a suspected
difference after using the tool (1 (40)=1.896, .Q=.0656) (Question 27 and 32).
36
@ •
Those who were more confident both before (M=2. 733) and after (M=2.467)
handling the tool were less likely to heed the warning than those not as
confident before (M=3.92) and after (M=3.44).
Familiarity with the tool was also found to affect whether one would
heed a warning using chi-square tests (Question 17, 18). Those who have
worked with tools (x 2 (1, N=40)=5.538, Q=.0186 with continuity correction,
<!>=.427), and those who have used a similar tool (x 2 (1, N=40)=5.444,
Q=.0196 with continuity correction, <!>=.422), were less likely to heed a
warning.
A significant relationship was also found between those who would
heed a warning and whether they have been injured using the tool
(Question 33) (x 2 (1, N=40)=5.056, Q=.0245 with continuity correction,
<!>=.417). Those who were injured before using a similar tool were more
likely to heed the warning.
Two unexplainable differences were also found. At-test comparison
found a significant difference between those who would heed a warning
and how serious of an injury they felt would occur after handling the saw (1
(38)= -2.049, Q=.0474). Differences between the groups indicate that those
who felt that a more serious injury would occur (M=S.O) actually complied
with the
warning~
than those who felt a less serious injury would occur
(M=3.72).
The other unexplainable difference using a chi-square comparison
involved those who knew of others who were injured using any tool (x 2 (1,
N=40)=3.687, Q=.0549 with continuity correction (x 2 =5.225, Q=.0223
without continuity correction) <1>=.361) (Question 34a). This result indicates
that those who did not know of others injured using the tool were more likely
37
to heed the warning (1 0 out of 11) than those who knew of others injured
(15 out of 29). It can be argued that the marginal number of 11 is fairly
small when using proportional data comparisons, and thus the result may
be unreliable.
These results indicate that confidence and familiarity with the tool may
affect whether one would heed a warning. Specifically if one is more
confident and/or more familiar in using a product, it is less likely that one
would comply with a warning. Also if one was personally injured using the
tool, it is more likely that the person would comply with the warning but not
necessarily if they knew of others injured.
Recall Danger
The only significant difference found using a chi-square comparison
was the relationship between whether one could recall the danger of the
warning message ("can cut") and use of a similar tool (Question 18). Those
who used a similar tool were less likely to recall the danger (x2 (1,
N=38)=4.581, Q=.0323 with continuity correction, <1>=.402) than those who
have not used a similar tool.
Recall Cause
No significant differences were found between whether one would
recall the cause of the warning message ("blade") and perception and prior
use of the product.
Recall Avoidance
The only significant relationship found using a chi-square comparison
was the use of a similar tool and whether one could recall the avoidance
message ("wear gloves") (x 2 (1, N=38)=3.701, Q=.0544 with continuity
correction (x2 =5.293, Q=.0214 without continuity correction), <1>=.373).
38
Those who have used a similar tool before were less likely to recall the
avoidance message than those who have not used a similar tool.
Differences Between Sex
The following differences based on sex were found:
1.
More females read the warning than males (x 2 (1, N=63)=3.437,
Q=.0638 with continuity correction (or 2 =4.459, Q=.0347 without continuity
x
correction) <1>=.266).
2.
(Question 17) "Have you worked with electric hand tools before?" (x 2 (1,
N=98)=18.05, Q=.0001 with continuity correction, <j>=.452) More males have
worked with hand tools before than females.
3.
(Question 18) "Have you used the tool, or something very similar to it
before?" (x 2 (1, N=98)=21.921, Q=.0001, <1>=.473) More males have used
the tool before than females.
4.
(Question 19) "When was the last time you used the tool?" (1 (53)=-.311,
Q=.003) Males (M=3.333) more recently used the tool than females (M=5).
5.
(Question 20) "About how often do you use the tool?" (1 (52)=-2.596,
Q=.0122) Males (M=3.538) use the tool more often than females (M=4.933).
6.
(Question 22 and 28) "How did you feel about its ease of use before the
experiment?" and "How easy is it to use now that you have performed the
experiment?" Males felt more at ease before (M=2. 735) (1(96)=-3.436,
Q=.0009) and after (M=2.367) (1(96)=-4.44, Q=.0001) the task than females
before (M=3.51) and after (M=3.347) the task.
7.
(Question 23 and 29) "How did you feel about how safe it was to use
before the experiment?" and "How safe is the product to use now that you
performed the experiment? Males felt the product safer to use both before
(M=92) (1(96)=-3.814, .Q=.0002) and after (M=2.347) (1(96)=-3.847, .Q=.0002)
the task than females before (M=3.592) and after (M=3.245) the task.
39
8.
(Question 24 and 30) "How did you feel about how likely an injury may
occur before the experiment?" and "How likely is an injury to occur now that
you performed the experiment? Females felt it more likely to be injured
both before (M=2.367) (1(96)=-2.132, Jl=.0356) and after (M=3.061)
(1(96)=-3.692, Q=.0004) the task than males before (M=2.367) and after
(M=2.122) the task.
9.
(Question 25 and 31) "How confident were you in using the tool before
the experiment?" and "How confident are you in using the tool now that you
performed the experiment?" Males were more confident both before
(M=1.98) (1(96)=-5.582, Q.=.0001) and after (M=1.898) (1(96)=-5.287,
Q=.0001) the task than females before (M=3. 735) and after (M=3.51) the
task.
10. (Question 34a) "Do you know of anyone who was injured using any
tool?" More males knew of others injured using tools than females (x 2(1,
N=98)=4.24, Q=.0395 with continuity correction, 4>=.231 ).
11. (Question 35) "Have you worn protective clothing before?" More males
have used protective clothing before than females (x 2 (1, N=98)=7.733,
Q=.0054 with continuity correction, 4>=.304).
There were no differences between males and females on noticeability,
compliance and recall of the warning sign.
Product Hazardousness
Data on the dependent measures were gathered and compared
between subjects who handled the circular saw (high product
hazardousness) and subjects who handled the jigsaw (low product
hazardousness). Results presented in Figure 2 indicate those who handled
the jigsaw were less likely to notice, read and comply with the warning than
40
100
90
80
70
(/)
Q)
-
g> 60
c
Q)
(.)
Ci5
0..
so
40
30
20
10
Noticed
Read
Heeded
Figure 2. Product Hazardousness
Subjects who noticed, read and heeded the warning based
on product hazardousness (based on total subjects)
41
those who handled the circular saw. Chi-square tests were conducted on
this data, and significant differences were found between the circular saw
and jigsaw for those who noticed the warning (x2 (1, N=98)=4.196, p=.0405,
<1>=.207), read the warning (x2 (1, N=98)=7.52, <1>=.0061) and complied with
the warning (x2 (1, N=98)=8.38, Q=.0038, <1>=.292). Therefore, the results
indicated that based on all subjects, more subjects noticed, read and
complied with the warning when using the circular saw than the jigsaw.
Another set of analyses was conducted to ascertain whether differences
between the products affected subjects' propensity to read the warning,
contingent upon noticing the warning. A chi-square test was conducted and
a suspected difference resulted (x 2 (1, N=63)=3. 71, Q=.0541, <1>=.243).
Increasing power of the test, by simply increasing the number of subjects in
the experiment may have resulted in a significance difference at the .05
level, thus it is suspected that a difference may exist. This result indicates
that contingent upon noticing the warning, product hazardousness affected
whether subjects read the warning. The next analyses was conducted
upon only those who read the warning. A chi-square test was employed to
ascertain differences in compliance based on product hazardousness. No
significant differences were found (see Figure 3). This lack of significance,
however, may be due to low power resulting from so few subjects reading
the warning.
Dependent measures of recall were also compared between the two
groups of low and high product hazardousness. Analysis of only those who
read the warning are shown in Figure 4. The only observed trend indicate
those who handled the jigsaw were consistently lower in recall than
subjects who handled the circular saw.
Nonetheless, chi-square tests
42
80
60
Cl)
Percentage of subjects
who NOTICED warning
g'
'E
Cl)
~
40
Cl)
c..
20
Circ Saw
Jigsaw
80
Percentage of subjects
who READ warning
(Total based on those
who noticed warning)
60
Cl)
g'
~ 40
~
c..
20
CircSaw
80
Percentage of subjects
who COMPLIED with
the warning
(Total based on those
who read warning)
Jigsaw
73.1%
60
QJ
Ol
m
'E
Cl)
~
40
Cl)
c..
20
Circ Saw
Figure 3.
Jigsaw
Product Hazardousness differences contingent upon
prior behavior
l
•
,, .
43
100
90
80
70
Circ
~ 60
Jig
Saw
58.3%
Jig
Saw
0)
C11
c
Q)
(.)
50
.._
Q)
fl..
40
30
20
10
Recalled
Danger
"Blade"
Figure 4.
Recalled
Cause
"Can Cut"
Recalled
Avoidance
"Wear Gloves"
Product Hazardousness
Subjects who recalled the warning message (included only
those who read the warning)
-
~-
--
-~
---
-
- - --
----
~-----
-
-~~~~
44
exhibit no significant differences between product hazardousness and
recall of the warning messages.
The overall results on the dependent variables indicate that perceived
differences between the two electric saws affect whether subjects will
notice, read and comply with warnings. The data also suggest that even if
subjects notice the warning, there is more of a tendency to read the warning
if it is placed on the circular saw than on the jigsaw. Recall results suggest
that if people read the warning, there is no difference between the recall of
one portion of the warning message over another portion of the warning
message as a function of the perception of the product.
Warning Sign Design
Data on the dependent measures were gathered and compared
between subjects exposed to the three different warning signs ("words
only", "pictograph only" and both "words and pictograph"). As seen in
Figure 5, there is a consistent decline in all label conditions in the number
of subjects who first notice the warning, read the warning and heed the
warning. The raw data appear to suggest that the warning sign with "words
only" and with both "words and pictograph" had consistently higher
response percentages than those exposed to the warning sign with
"pictograph only", but complex chi-square tests indicate no significant
differences of noticing, reading or heeding based on type of warning sign.
Differences in willingness to read the warning were analyzed based on
those who noticed the warning and no significant results were found. Also
differences in compliance were examined on those who read the warning
and again no significant difference in type of warning sign was found (see
Figure 6). Figure 7 presents the recall data. Complex chi-square tests
were conducted between warning sign type and recall of the warning
message, and no significant differences were found. These results indicate
45
100
90
80
Pictograph
only
53%
words
only
78%
70
Pictograph
only
26.5%
(/)
~ 60
C'Cl
words
only
46.9%
c
Q)
2Q) 50
c..
40
words+
pictograph
43.8%
Pictograph
only
17.6%
words+
pictograph
31%
30
20
10
Noticed
Read
Heeded
Figure 5. Warning Sign Type
Subjects who noticed, read and heeded the warning based on
type of warning sign (based on total subjects)
46
Percentage of subjects
who NOTICED warning
Words only
Pictograph
only
80
Words+
Pictograph
70%
60
Percentage of subjects
who READ warning
(Total based on those
who noticed warning)
~
c:
~
40
rf.
20
Words only
Pictograph
only
80
Words+
Pictograph
71.4%
60
Percentage of subjects C1l
who COMPLIED with
~
c
the warning
~ 40
(Total based on those
C1l
who read warning)
a..
20
Words only
Pictograph
only
Words+
Pictograph
Figure 6. Warning sign differences contingent upon prior behavior
47
100
90
80
70
words+
Pictograph
Pictograph
pictograph
only
only
57%
33.3%
66.7%
Pictograph
words
words
only
words+
only
only
77.8%
pictograph
73.3%
73.3%
73.3%
words+
pictograph
64.3%
(/)
(I)
0>
co
60
c
(I)
e
(I)
c...
50
40
30
20
10
Recalled
Danger
"Blade"
Figure 7.
Recalled
Cause
Can Cut
Recalled
Avoidance
"Wear Gloves"
Warning Sign Type
Subjects who recalled the warning messages based on
type of warning sign
48
that there is no difference in whether subjects will notice, read, heed or
recall warnings based on type of warning sign.
Interactions between Independent Variables
To identify interactions between product hazardousness and type of
warning sign, simple effects were conducted and the following results were
found. (see Figure 8) Those who handled the circular saw tended to read
the warning with "words+pictograph" than "pictograph only"(x2 (1,
N=34)=2.951, Q.=.0858 with continuity correction, (or x 2=4.25, Q=.0393
without continuity correction) <1>=.354).
Also more subjects read the
"words+pictograph" warning when placed on the circular saw than on the
jigsaw (x 2(1, N=34)6.222, Q=.0126 with continuity correction, (or x 2=8.127,
Q=.0044 without continuity correction) <1>=.504 ). There was a tendency to
comply with the warning with "words only" when placed on the circular saw
than the jigsaw (x 2 (1, N=32)=2.473, Q=.1158 with continuity correction (or
x 2=3.865, Q.=.0493 without continuity correction) <1>=.348). Similarly those
exposed to the "words+ pictograph" sign also complied with the warning
when placed on the circular saw than the jigsaw (x 2 (1, N=32)=3.636,
Q=.0565 with continuity corretion, (or x 2 =5.236, Q=.0221 without continuity
correction) <1>=.405). No simple effects were found for those who noticed the
warning. Also no simple effects of recall were found, however it may be due
to the lower power resulting from so few subjects reading the warning
message.
49
81.25
81.25
circular saw
80
7
Percentage
Noticed
60
~----·
40
43.75
43.75
jigsaw
20
Words only
Pictograph
only
Words+
Pictograph
80
68.75
circular saw
56.25
Percentage 60
Read
40
18.75
jigsaw
20
Words only
Pictograph
only
Words+
Pictograph
80
60
50
circular saw
40
Percentage
Complied
20
12.5
Words only
Figure 8.
12.5
Pictograph
only
jigsaw
Words+
Pictograph
The data plots exhibit overall percentage of subjects
on the dependent variables
50
Recall Pata
Recall of the warning sign was also coded on a 3-point scale. A score
of "0" was assigned to a totally incorrect response, a score of "1" was
assigned for a partially correct response, and a score of "2" was assigned to
a correct response. Given the three possible warning messages, a
subject's total recall score ranged from 0-6. A 2-factor analysis of variance
test conducted on the independent variables of product hazardousness and
type of warning sign design with the recall data scores found no
significant differences. Thus subjects recalled the warning message equally
well across all experimental conditions.
Confidence Ratings
Data on confidence of comprehension of the warning sign was also
gathered (Question 9). Each subject who read the warning message rated
their confidence of comprehension on a scale from 1 to 7 (1
= not confident
at all, and 7 =very confident). A 2-way analysis of variance was performed
to determine any significant main effects or interactions of the independent
variables based on the confidence ratings. No significant differences were
found. These results indicate that subjects who read the warning equally
understood the warning across all experimental conditions.
Overall Analyses
Percentages of all subjects who ncticed, read and heeded the warning
were accumulated (Question 1: "Did subject heed warning?", Question 2:
"Did
you~
a warning?", Question 6· "If you saw it, did you re.aQ it?"). The
percentages as shown in Figure 9 indicate that about 64.3% of the subjects
saw the warning, but the percEntage decreases to 38.8% who read the
warning and decreases again to 25.5% of the total who actually complied
51
100
90
80
70
64.3%
CJ)
Cl>
-e
0)
60
~
c
Cl>
Cl>
50
a..
38.8%
40
30
25.5%
20
10
Noticed
Read
Heeded
Figure 9. Overall percentages of subjects who noticed, read and
heeded the warning
52
with the warning. A test to find a significant difference between the groups
was performed, and significant differences were found to exist between
those who saw the warning and both read the warning (l-=3.5714, Q<.05,
N=98), and heeded the warning (Z-=5.457, Q<.05, N=98) and between those
who read the warning and heeded the warning (l-=1.99, Q<.05, N=98).
To analyze overall recall of the warning sign, responses gathered on
recall of the danger of the warning hazard (Question 10: "What injury could
occur?"), the cause of the hazard (Question 11: "What could cause the
injury?"), and the avoidance of the hazard (Question 12: "How could you
avoid it?") were combined and analyzed dichotomously by assigning an
"incorrect" response to those who received a "0" score (totally incorrect),
and by assigning a "correct" response to those who received a score
of "1" {partially correct) or "2" (fully correct). Out of those who recalled the
warning messages, most subjects recalled the avoidance message
(73.8%), the least number of subjects recalled the cause of the hazard
message (57.1 %), and those who recalled the cause of the hazard was
slightly above the number of subjects who recalled the danger message
(60.5%) (Figure 10). Tests for significance of difference between
proportions on the recall data show no differences between recall of the
warning messages.
Additional Response Data
Additional data were collected and analyzed on confidence of location
of warning, color, physical appearance and attraction of words or
pictograph of the warning, on prior experience and use of protective gear,
and experimental realism.
Confidence of Location
Question 4 asked subjects who noticed the warning to rate how
confident they were that the warning was placed where they thought it was.
A 2-way analysis of variance was performed on differences between
53
100
90
80
70
(/)
Q)
60
Ol
-co
c
Q)
(.)
.......
50
Q)
0..
40
30
20
10
Recalled
Danger
"Can Cut"
Recalled
Cause
"Blade"
Recalled
Avoidance
"Wear Gloves"
Figure 10. Overall percentages of subjects who recalled the warning
message of Danger (can cut), Cause of the injury (blade)
and Avoidance (wear gloves)
54
independent variables and confidence of location, and a main effect was
found on product hazardousness (E(1 ,55)=4.54, Jl=.0376). People were
more confident of warning sign location on the jigsaw (M=6.583) than the
circular saw .(M=5.919).
Recall of Color and Design of Warning Sign
Question 5 ascertained whether subjects could recall the color of the
warning sign. Most who noticed the warning responded correctly, and a
few responded by simply guessing the color. Chi-square tests revealed no
significant differences on the independent and dependent variables.
Question 13 requested those subjects who read the warning to draw a
picture of the warning. All subjects who recalled correctly or incorrectly the
warning sign drew the recalled information on the physical drawing. Thus,
no discrepancies occurred between recall and the drawing.
Comments on Noticing. Beading and Complying with Warning
Questions 14, and 15 probed subjects to give reasons why they may
have neglected to notice, read or heed the warning. Most responses
centered upon reasons of familiarity and experience with the product.
Those familiar with its use argued that they were comfortable with its
operation, and thus felt they already knew the safety precautions necessary
for operation, and therefore either did not notice, read or heed the warning.
Other major reasons given were "concentrating on the task" or "assumed I
knew what it said." Results from Question 14c "If you saw, read and
understood the warning, do you think you would have put on gloves?"
found through a chi-square test a significant difference between products
(x 2 (1, N=95)=.0443, Q=.0443, <1>=.206). Subjects said that if they took the
time to read and understand the warning they felt they would more likely
heed the warning placed on the circular saw than the jigsaw.
55
Question 16 probed subjects as to why they put on gloves. Most (67%)
said it was due to the warning, and wanted to be as careful as possible.
Four of the 24 subjects who complied admitted they would normally put on
gloves irrespective of the sign. Question 16c also probed specifically those
who were given the warning sign with "words and pictograph," what portion
of the sign attracted their attention more. Interestingly enough, based on
the responses gathered on this question 57% felt that the words attracted
their attention, even though the words were positioned below the
pictograph. It is felt that those who read the warning tended to recall the
words more than the pictograph, and thus felt the words attracted their
attention.
Prior Use of Protective Clothing
Question 35 asked subjects whether they have ever worn protective
clothing before, such as face masks or eye goggles. Chi-square tests on
this question and the dependent variables found no significant differences.
Experimental Realism
Questions 36 to 38 asked subjects whether the experimental setup and
task was realistic and comfortable. Most responded by saying that the task
was realistic and they would perform similarly if at home. A few suggested
that the work table was placed too high, or an extra tool normally used
(mitre board) was missing. Nonetheless an overwhelming agreement was
that the task was realistic.
Question 39 asked subjects if they normally read instructions. Also an
overwhelming answer of "yes," resulted. Whether this is in fact true or not
was not verified in this experiment.
Question 40 asked whether subjects felt the warning message was
reasonable. Again, most felt that the warning was reasonable, and the
standard response was that, "you can't be too cautious."
Discussion
Overall findings revealed that when a warning sign is placed on a
product, over half of the people may notice it but only about 26% will
actually heed it. These results are attributed to differences in perceived
hazardousness and type of warning sign used in this study. Additional
factors such as familiarity and prior experience with the product, confidence
in using the product, and prior injury have also been found to influence
warning effectiveness. Detailed discussion on each of these factors are
presented below.
Product Hazardousness
As hypothesized, more people noticed, read and complied with the
warning placed on the product perceived to be more hazardous than on the
product perceived to be less hazardous (refer to Figure 2). These results
are consistent with Godfrey et al. (1983) and Godfrey et al.'s (1984) studies
which found (from surveys) that people who perceived products to be
hazardous said they would tend to look for warnings on the product. More
detailed analysis of the data revealed that the number who read the
warning was one-third as great (52%) as the number who noticed the
warning (74%), and the number of subjects who complied with the warning
was one-third as great (38%) as the number who read the warning.
Compared to this amount of decline, the decreasing number of subjects
who used the jigsaw from noticing, to reading, to complying with the
warning was noticeably greater: those who read the warning was one-half
the number (25%) who noticed the warning (54%), and those who complied
with the warning was one-half the number who read the warning (12.5%).
Subjects who did not notice the warning were asked whether they
would have complied with the warning if they noticed, read and understood
56
57
the warning. Subjects who were exposed to the circular saw admitted that
they would more likely heed the warning than subjects given the jigsaw.
Thus the circular saw perceived to be more hazardous influenced subjects
to continue to notice, read and finally comply with the warning. Subjects
were generally more cautious using the circular saw than the jigsaw.
Design of Warning Signs
Data from the control group showed that none of the subjects actually
put on gloves, but with the addition of the warning sign to the product,
overall results showed that 25.5% of the experimental subjects complied
with the warning. The condition that elicited the highest percentage of
compliance (circular saw with warning sign with "pictograph+words") was
also 50%. Thus it is obvious with the addition of a warning sign on a
product, some people will be influenced by its message, and some may
heed the warning. This however, does not guarantee that placing warnings
on~
product will be sufficient to facilitate cautious behavior (as other
perceptual attributes as perceived hazardousness, prior use and
experience with the product will affect behavior) but it does suggest that the
use of warnings on some types of products will influence some people, as
shown in this study. The result is consistent with other studies on
compliance (Zlotnick, 1982; Wogalter et al, 1985; Godfrey et al. 1985). But
as found in Strawbridge's (1986) study, the overall percentage of those who
complied is fairly low-- in this experiment only 25.5% complied which was
influenced by the low compliance with use of the jigsaw, which averaged
12.5% compliance. Those who handled the circular saw tended to comply
with the warning more (22.2% to 50% compliance).
The type of warning sign had no differential effect on noticeability. This
is consistent with the hypothesized contention that since features that
influence conspicuity (size, location, brightness, color, highlighting) are
58
constant across all warning sign conditions, no effects of conspicuity were
expected. However comments from subjects who were exposed to the
warning with both "pictograph+words" revealed that they felt the words
attracted their attention more than the pictures (8 out of 14). It is
conceivable that since words are always used to communicate a message
or information, there may be a tendency for subjects to take a second look
and consciously take notice of the warning, whereas the use of pictures are
not always used to communicate information. Many times pictures are
simply used for decorative purposes, and thus are simply ignored by some.
This being the case, the use of words on warnings may be an important
factor to facilitate and encourage noticeability of warnings.
This result may also suggest that pictographs do not attract attention
more than words, and do not facilitate whether people will notice warnings.
Nonetheless pictographs influence confidence levels of subjects (see
Confidence of Product Use below). If confidence is important, then the
addition of a pictograph is important in the design of a warning. Also
pictographs may still serve another purpose. If previously exposed to the
pictograph people may recognize and recall its message and thus heed the
warning. Based on studies of recognition and recall (Standing 1973; Paivio
et al. 1968) pictures were identified and recalled correct more often than
words. Since this current study examined the performance of subjects who
were not previously exposed to the warning sign, we do not know whether
an initial exposure to the pictograph over time and extended use would
enable easier and faster recognition of the sign compared to the sign with
"words only."
There was also no main effect of warning sign on the willingness to read
warnings. However, a simple effect difference between warning signs was
revealed when data for the circular saw was analyzed. The result indicated
that subjects exposed to the warning with both "pictograph+words" read the
59
warning more than those exposed to the warning with "pictograph only."
This result can be partially attributed to the difference in level of confidence
found between warning signs. (see below Confidence of Product Use) It
was shown that subjects were more confident with the tool when the
warning sign with "words only" was used and least confident with the
warning with both "words+ pictograph." Those who are uncertain and less
confident in performing the task would tend to be more cautious by reading
and complying with the warning. In this case, the warning sign with both
"words+pictograph" instilled uncertainty and low confidence which may
have encouraged subjects to read and comply with the warning.
For those subjects who noticed but did not read the warning, some
commented that they thought they knew what the warning said (28%). A
couple of these subjects also mentioned that caution and warning signs
were seen all the time. This comment suggests that people may ignore
warning messages placed on products because of the prevalence of
warning signs on such products. Most messages communicate some form
of the message, "Caution," or "Danger," and therefore individuals may
assume the general message is to "Be Careful," and do not read the
warning. When people are involved in completing a task, extra effort is
required to take time to read and understand a warning sign. Some people
simply do not take this extra time to notice and read the sign.
There was no difference in comprehension of the warning message
between any of the experimental conditions and therefore suggests that all
types of warning signs were equally understood. This data could be
confounded by the fact that subjects may have reJ.1 they understood the
message, when in fact they did not fully read the warning, but just
contextually interpreted its fully meaning by portions read and recalled.
Analysis of those who read the warning indicate that all except one subject
understood the warning (this subject actually recalled one portion of the
60
warning correctly and even heeded the warning) and two additional
subjects said they understood the warning and yet could not recall any
portion of the message correctly. All other subjects who read the warning
felt they understood the warning and were able to recall at least one portion
of the warning message correctly. Thus, if comprehension is based on
recalling at least one portion of the warning message in addition to feeling
as though they understood the warning, than 35 out of 38 subjects or 92%
understood its message.
The type of warning signs used in this study also did not affect the level
of recall of the warning messages. But when the average recall measure
was calculated, an average of 3. 71 out of the total 6 points was found. This
implies that people generally recalled just over half of the message, and in
fact out of those who read the warning only 12 subjects out of 38 (31.6%)
were able to recall the entire message correctly. Out of the remaining
number, 12 subjects recalled only one message, and 12 subjects recalled
two out of the three messages correct. Two subjects also could not recall
any portion correctly. Many of the subjects who read the warning simply
scanned it and recalled portions of the message, but there was no
difference in terms of which portion they recalled.
Results also indicated that the type of warning sign used did not affect
compliance. It was hypothesized that subjects given a warning with both
"words+pictograph" would comply with the warning more than the warning
with "words only" and with "pictograph only." When reviewing the raw data,
more people did heed the warning with words and pictograph (31% or 10
out of 32), not that much more than for "words only" (28% or 9 out of 32) and
almost twice as much for "pictograph only" (17.6% or 6 out of 34). However
there was no significant difference between signs.
61
Familiarity and Experience
Results revealed that familiarity and prior experience with the product
influence whether subjects will notice, read, and comply with the warning.
Thirty-nine (39%) of those who did not notice the warning commented that
they were familiar with its use, either had personally used it, or had seen it
being used. This response is supported by the study conducted by Dorris
and Purswell (1977) who found that when subjects were given hammers to
use, no one even noticed the warnings placed on the hammers. The
familiarity of the product probably influenced their behavior, and out of 100
people, not one person even noticed the warning placed on the hammer.
Twenty-eight percent (28%) of those who did not read the warning
commented that they felt comfortable using the tool from prior experience,
thus did not take the time to read the warning. Questionnaire responses on
frequency and recency of product use also affects recall of the danger
message and the avoidance message. This is consistent with Godfrey et al.
(1984) who also found that familiarity may affect recall. Also Wright et al.
(1982) found that users would tend to read instructions less on those
products perceived to be familiar. Also instructions of those products that
were frequently used were also less likely to be read.
Results also suggested that more females than males read the warning.
However this result is attributed to the difference in familiarity and
experience between the sexes. More males had prior experience and
familiarity with the tools (39 out of 49) than females (16 out of 49). Also
when a comparison was made between those familiar and those unfamiliar
with the tool, it was uncovered that the males less familiar with the tool read
the warning more often than males who were more familiar. Therefore the
difference found between males and females are attributed to the degree of
familiarity with the product.
62
Familiarity also affected recall of the warning messages. Those who
were less familiar with the tool recalled the danger message ("can cut") and
the avoidance message ("wear gloves") more than those who were more
familiar with the tool. This is consistent with Godfrey et al. (1984) who also
found that familiarity may affect recall.
Confidence of Product Use
Results revealed that subjects were more confident using the product
perceived to be less hazardous Uigsaw) than the product perceived to be
more hazardous (circular saw).
It was also shown that people more
confident with use of the product were less likely to read or comply with the
warning. Thus the influence of confidence affects whether people will read
and comply with the warning.
There was also a significant difference between warning signs and
confidence level. Specifically subjects exposed to the warning that
portrayed the hazard with both "pictograph+words" were less confident in
performing the task than those exposed to the warning with "words only." It
is conceivable that the redundancy in warning message with both words
and pictograph may influence confidence level, and thus affect whether
subjects will read and comply with the warning. The pictograph may
support the warning message by pictorially portraying hazard to the subject,
and promote the feeling of uncertainty and less confidence than the
warning sign which had no pictograph.
Since it has been shown that people less confident will tend to read and
comply with warnings, the use of "pictograph+words" may encourage this
likelihood that people will comply. The use of this warning sign may be
advantageous when applied to the product already perceived to be
hazardous (i.e. circular saw). When we compare the percentages of those
who noticed the warning, we see that the same number of people noticed
63
the warning with "words only" (81.25%) as with "pictograph+words"
(81.25%). This is consistent with the comments made by subjects who said
that the words seem to attract their attention more than the pictures, for an
equal number of subjects noticed the warnings with words on them, but
least with the warning with "pictograph only." However when we review the
percentages of subjects who read the warning, we find that the percentage
of those exposed to the warning with "words only" is now lower (56.25%)
than the warning with both "words+pictograph" (68.75%). Once subjects
saw the warning with both "words+pictograph", there was a tendency to
continue and read and comply with the warning (43.75% compliance for
"words only" and 50% compliance for "words+pictograph"). In fact there
was a significant difference between the warning sign and the willingness
to read the warning when placed on the circular saw. More people read the
"pictograph+words" warning than the "pictograph only" warning sign.
No such differences were found with data gathered on the jigsaw, and
in fact results indicate that subjects complied equally across all warning
sign conditions (12.5%). Thus, the warning sign with both
"pictograph+words" may influence subjects' level of confidence, and affect
whether they will read and comply with the warning, particulary if the
product to be used is already perceived to be hazardous.
Prior Injury
Those who were personally injured using tools were more likely to heed
the warning than those who were not previously injured, or even those who
know of others injured. Out of the 98 subjects in the experimental pool, 9
subjects were personally injured in the past and all complied with the
warning. Thus, there may be a tendency toward protecting oneself if injured
in the past.
(l
'
64
Other Considerations
A few issues must also be addressed. The first issue pertains to the
reliability of the questionnaire responses gathered in this experiment. It is
possible that the questionnaire responses regarding product perceptions
may have been influenced by the questions asked in the interview process.
Subjects answered the questionnaire .af1m performing the task, and .af1.e.r
being asked information about whether they noticed or read the warning
sign. This prior use of the product and questioning by the experimenter
may have influenced their interpretation and perception about the products,
i.e. they may have thought the jigsaw was easier to use because they did
not notice, read or comply with the warning.
The second issue pertains to the generalizability and realism of the task.
The majority of the subjects felt the setup was realistic and normally
performed the task the way they would at home. A few (8 out of 98) felt that
they would have attempted to become more familiar with the saw, either by
reading instructions, talking with others, or testing it out before actually
performing the task. The remaining subjects felt the task was realistic.
There were a few subjects who were excused from the experiment (a
total of 6: 5 females and 1 male). All subjects were given the opportunity to
decline from participating in the experiment, and these subjects felt that they
would not even attempt to do the task on their own, thus they were excused.
Others in the experiment may have participated because of a sense of
"security" given by the experimenter present in the same room, and two
subjects out of 98 admitted that this presence may have affected their
performance by offering comments as, "You told me to do the task, so thats
what I was doing," when asked if the situation was realistic. This type of
experiment may be interpreted by subjects as "not dangerous" because of
the experimental setup in university facilities. Nonetheless, all others in the
experiment felt that the experimental setup and task were fairly realistic, and
65
expressed they would tend to perform similarly if at home by themselves.
These results support the generalizability of behavior to real-world
situations.
There were also significant differences between the products on ease
and safety of use: more people felt the jigsaw was easier and safer to use
than the circular saw. These factors may be influential in affecting subjects'
confidence levels and perceived hazardousness of the situation. If so, then
perceived safety and ease of use may influence whether subjects would
notice, read, comply with and recall warnings.
These factors, in addition to others gathered in the questionnaire, as
familiarity (recency of use, frequency of use) experience with the product,
and confidence with product use, which were found to be significantly
related to warning effectiveness need to be further studied through direct
observations to help validate the results of this current study.
Conclusion
The use of warning signs has a positive effect. Of course this is
dependent upon product perception (hazardousness, familiarity, and
confidence levels) but results from this study suggest that when a warning is
placed on a product, some people may notice, read and heed the warning.
When no warning sign is used, there is a greater possibility that no one will
act cautiously. Thus, if it is desired to influence at
least~
of the
population, a warning sign may be effective.
Although warnings may be effective when compared to the use of no
warning, we cannot ignore the percentages of those who actually noticed,
read and complied with the warning. Only over half of the subjects noticed
the warning (64%) and only 25.5% complied with the warning! Other
factors influenced behavior (as hazardousness, familiarity and confidence)
and the use of the warning was insufficient to persuade most people to
66
comply with its message. In reviewing the experimental data, the best
condition to elicit compliance was with the product that was perceived to be
more hazardous (circular saw) than the other product perceived to be less
hazardous (jigsaw) with the warning sign with both words and pictograph:
the percentage was 50% compliance. Unfortunately, we cannot always
predict the "hazardousness" of the product or the familiarity levels of people
who will use the products, thus the use of warnings cannot guarantee that
people will be cautious.
The use of pictographs on warnings did seem to influence the
confidence levels of those exposed to the product perceived to be
hazardous. When placed on the circular saw more people read the
warning with "pictograph+words" than "words only." People were also
observed reading and heeding the warning more with the circular saw, thus
the use of pictographs to convey a sense of hazard may influence the
confidence levels of subjects, and thus is suggested to be used. Subjects
also commented that they noticed the words more on the warning than the
pictograph, and in fact the level of response with the use of the warning with
"pictograph only" was consistently lower than the other label conditions,
thus the use of words may be also important in facilitating noticeabiltiy of
warnings. Thus we conclude that both pictograph and words should be
used, when possible, to convey warnings. As this study has shown, the use
of words and pictographs on a warning will especially be advantageous
when applied to a product already perceived to be hazardous.
We must still be aware that the application of warnings must be used
with care. People are becoming overloaded with warning signs-- they see
the same types of warnings on many types of products, with messages that
simply imply, "Be Careful." If people are primarily involved in performing a
task, there may be a greater tendency to concentrate on the task and to
ignore extraneous signs that require conscious attention, such as the
67
presence of warnings, instructions, etc. This behavior may be more
prevalent for those familiar or confident with use of the product. Of course it
is possible that since warnings are becoming standard practice, people
may simply act more cautious if they notice its presence, irrespective of
whether they read, fully understand or fully comply with its message. This
cautious behavior may be advantageous in of itself, influenced by the
simple presence of a warning.
On the other hand, if warning signs are designed consistently the same,
people may recognize the label as a warning sign, but then fail to read the
sign and ignore its message, making assumptions about its meaning. We
must alleviate this problem by training and educating the public to the
hazards and dangers evident in injury data, and we must encourage
product designers to design and build products that are safe to use.
However there still exists products that are not inherently safe to use,
thus the use of warnings are still in demand. Additionally we cannot predict
which products will be perceived to be more hazardous than others, and
which will be more familiar. Therefore, ultimately, we need to facilitate and
encourage continual improvement in developing safer products to alleviate
the simple need to warn.
68
References
American National Standards Institute. (1973). ANSI specification for
accident preyentsigns. (Z35.1-1973). New York, NY: American
National Standards Institute.
Booher, H. (1975). Relative comprehensibility of pictorial information and
printed words in proceduralized instructions. Human Factors, 11(3),
266-277.
Bresnahan, T., & Bryk, J. (1975, January). The hazard association values
of accident-prevention signs. Professional Safety. 17-25.
Browning, R.L. (1980). The loss rate concept in safety engineering. New
York: Marcel Dekker.
Cahill, M.C. (1973). Interpretability of graphic symbols as a function of
context and experience factors. Journal of Applied Psychology.
376-380.
Cochran, D., Riley, M., & Douglas, E. (1981 ). ProceedinQs of the Human
Factors Society- 25th Annual Meeting, 1981, 395-399.
Collins, B., Lerner, N., & Pierman, B. (1982). Symbols for industrial safety.
(Report No. NBSIR82-2485). Washington, DC: National Institute of
Occupational Safety and Health.
Dewar, R., Ells, J., & Mundy, G. (1976). Reaction time as an index of traffic
sign perception. Human Factors.
~(4),
381-392.
Dorris, A.L., & Purswell, J.L. (1977). Warnings and human behavior:
implications for the design of product warnings. Journal of Products
Liability.
1. 255-264.
Dorris, A.L., & Purswell, J.L. (1978). Human factors in the design of
effective product warnings. Proceedings of the Human Factors
Society- 22nd Annual Meeting, 1978, 343-346.
69
Dorris, A., & Tabrizi, M.F. (1978). An empirical investigation of consumer
perception of product safety. Journal of Products Liability .
.2. 155-163.
Easterby, R.S., & Hakiel, S.R. (1981 ). Field testing of consumer safety
signs: the comprehension of pictorially presented messages. Applied
Ergonomics, 12.(3), 143-152.
Easterby, R.S., Hakiel, S.R., & Graydon, I.R. (November, 1980). Safety sign
conspicuity: the effect of sign size and position on detection. (Report
No. AD Report 89). Birmingham: Applied Psychology Department
University of Aston.
Eastman Kodak Co. (1983). Ergonomic design for people at work (Volume
I). Belmont, CA: Lifetime Learning Publications.
Ells, J., & Dewar, R. (1979). Rapid comprehension of verbal and symbolic
traffic sign messages. Human Factors, .lll. 161-168.
FMC, Corp. (1985). Product Safety Sign and Label System. Santa Clara,
CA: FMC, Corp.
Godfrey, S.S., Allender, L., Laughery, K.R., & Smith, V. (1983). Warning
messages: will the consumer bother to look? Proceedings of the
Human Factors Society -27th Annual Meeting, 1983.
Godfrey, S.S., & Laughery, K.R. (1984). The biasing effects of product
familiarity on consumers' awareness of hazard. Proceedings of the
Human Factors Society- 28th Annual Meeting, 1984, 483-486.
Godfrey, S.S., Rothstein, P.R., & Laughery, K.R. (1985). Warnings: do they
make a difference? Proceedings of the Human Factors Society- 29th
Annual Meeting, 1985.
Grandjean, E. (1985). Fitting the Task to the Man. London and
Philadelphia: Taylor and Francis.
Hammer, W. (1972). Handbook of system and product safety. Englewood,
NJ: Prentice Hall, Inc.
70
King, L.E. (1975). Recognition of symbol and word traffic signs. Journal of
Safety Research. 1, 80-84.
McCarthy, R., Robinson, J.N., & Finnegens, J. (1982). Warnings on
consumer products: objective criteria for their use. Proceedings of the
Human Factors Society- 28th Annual Meeting, 1984, 81-85.
McCormick, E., & Sanders, M. (1982). Human factors in engineering and
design (5th ed.). New York: McGraw Hill Book Company.
McGuinnes, J. (1977). Human factors on consumer product safety.
Proceedings of the Human Factors Society-21st Annual Meeting,
1977, 292-294.
Paivio, A., Rogers, T.B., and Smythe, P.C. (1968). Why are pictures easier
to recall than words? Psychonomic Science . .11(4), 137-138.
Peters, G.A. (November, 1983). Toward effective warning for automobiles:
a challenge to the trial bar. Trial Magazine, 19(11 ), 114-119.
Peters, G.A. (May, 1984). 15 cardinal principles to ensure effectiveness of
warning system. Occupational Health and Safety, 76-79.
Ross, K. (1981 ). Legal and practical considerations for the creation of
warning labels and instruction books. Journal of Products Liability. _1,
24-45.
Rothstein, P.R. (1985). Designing warnings to be read and remembered.
Proceedings of the Human Factors Society- 29th Annual Meeting,
1985.
Sampson, J.R. (1970). Free recall of verbal and non-verbal stimuli.
Quarterly Journal of Experimental Psychology. 22, 215-221.
Standing, L. (1973). Learning 10,000 pictures. Quarterly Journal of
Experimental Psychology.
~.
207-222.
Standing, L., Conezio, J., & Haber, N. (1970). Perception and memory of
pictures: single-trial learning of 2500 visual stimuli. Psychonomic Sci.
.ta, 73-74.
71
StatView 512+™. (1985) Statistical computer package for the Macintosh
computer. Distributed by Brainpower, Inc., Calabasas, California.
Strawbridge, J. (1986). The influence of position. highlighting and
imbedding on warning effectiveness. Unpublished master's thesis,
California State University, Northridge, Northridge, CA.
Walker, R., Nicholay, R., & Stearns, C. (1965). Comparative accuracy of
recognizing American and international road signs. Journal of
Applied Psychology.
~(5),
322-325.
Wogalter, M.S., Desailniers & Godfrey,S.S. (1985a). Perceived
effectiveness of environmental warnings. Proceedings of the Human
Factors Society- 29th Annual Meeting, 1985.
Wogalter, M.S., Fontanelle, G.A., & Laughery, K.R. (1985b). Behavioral
effectiveness of warnings. Proceedings of the Human Factors Society
-29th Annual Meeting, 1985.
Woodson, W. (1981 ). Human Factors Design Handbook. New York:
McGraw Hill Book Company.
Wright, P., Creighton, P., & Threlfall, S.M. (1982). Some factors
determining when instructions will be read. Ergonomics, ,£2(3),
225-237.
Zlotnik, M. (1982). The effects of warning message highlighting on novel
assembly task performance. Unpublished master's thesis, California
State University, Northridge, Northridge, CA.
Zwaga, H.J., & Boersema, T. (1983). Evaluation of a set of graphic
symbols. Applied Ergonomics. H.(1 ), 43-54.
APPENDIX A
Preliminary Experiment on Product Hazardousness
This pilot study identified two products different on "perceived
hazardousness." The products identified were two electric saws-- a circular
saw and jigsaw.
Before conducting the pilot study, various consumer products were
considered for evaluation. An attempt was initially made to center on a
group of products perceived to be hazardous. Based on a research study
conducted by Dorris and Tabrizi (1978), it was noted that product types
which had blades, or potential cutting surfaces were perceived to be more
hazardous than actual injury data indicated. Dorris and Tabrizi (1978)
speculated that if people were more cautious with these products due to the
perceived hazardousness of their use, then it was reasonable to assume
that injuries would be less. Thus, products with cutting surfaces were
inventoried. Among this group of products, the following were considered:
powered knives, blenders and mixers, unpowered hand saws, and
powered hand saws.
An attempt was then made to evaluate products within the same
category of products. Within the category of "powered hand saws," two
were selected for evaluation. These products were a circular saw and a
jigsaw. It was hypothesized that the jigsaw would be perceived to be less
hazardous than the circular saw based on subjects' judgements on the
likelihood of injury and the severity of injury.
Procedure
A questionnaire was developed to ascertain people's perceptions on
the two products. Questions were directed toward users' familiarity and
subjective estimates of the product's safety and ease of use. These
questions were rated on a 7-pt Likert scale. (see Figure 11)
72
73
The questionnaire was administered to 62 Introductory Psychology
students. There were 31 males and 31 females within the group. A circular
saw was shown to the subjects, and questions were answered relative to
the circular saw.
The same questionnaire was administered to 38 additional
Introductory Psychology students. There were 18 males and 20 females
within the group. A jigsaw was shown to the subjects, and questions were
answered relative to the jigsaw.
Results
Data gathered from the two groups were compared. Similar questions
were compared between the two groups using at-test. Results indicated
the only significant differences were on the questions, "How serious of an
injury may occur?" (1(98)=2.633, .Q<.05) and "How likely is an injury to
occur?" (1(98)=2.574,
~<.025).
Using the accepted formula for predicting risk or hazardousness
within the field of safety engineering (Browning, 1980; Hammer, 1972), data
from both questions were combined (Loss probability x Loss severity), and
a significant difference in perceived hazardousness resulted (p<.005). The
jigsaw was perceived to be less hazardous (M= 18.94 7) than the circular
saw (M=24.339).
Conclusions
The results indicated that the jigsaw and circular saw are different on
"perceived hazardousness."
74
Figure 11. Sample Questionnaire utilized in Preliminary Experiment to
ascertain differences in Product Hazardousness
Sex:
[
[
1
1
Male
Female
Age: _ _
Occupation: _ _ _ __
1.
2.
Have you used the tool, or something very similar to it before?
If no, go to question 4.
[ 1 Yes
[ 1 No
When was the last time you used the tool?
1 this week
1 this month
[ 1 three months ago
[ 1 six months ago
[
]
one year ago
[
]
two years ago
[
]
over 2 years ago
[
[
3.
About how often do you use the tool?
1 weekly
1 monthly
1 three months
[
]
every six months
[
]
yearly
[
]
every two years
[
]
every three years or more
[
[
[
~the
4.
Have you
5.
How easy is it to use?
1 very easy, no skill or knowledge of use was required
[
]
easy, with little skill or knowledge of use
[ 1 reasonably easy with some skill or knowledge of use
(
]
moderate in complexity with general skill or knowledge of use
(
]
somewhat complex, with fair knowledge or skill of use
[
]
complex with good knowledge or skill of use
[
]
very complex requiring extensive skill or knowledge of use
[
tool used before? If so, when and where?
75
6.
How safe is the product to use?
1 extremely safe
1 safe
1 somewhat safe
moderately safe
[
]
[ J somewhat unsafe
[
]
unsafe
[ 1 extremely unsafe
[
[
[
7.
How serious of an injury may occur?
1 no injury is possible
[
]
insignificant injury may occur
[
]
small injury may occur
[
]
injury may occur, but treatable at home
[
]
injury may require immediate care at home but does not
require hospital care
injury may require emergency hospital care
possible death
[
8.
How likely is an injury to occur?
highly unlikely
[
]
[
]
possible, but most unlikely
[
]
probably not occur
[
]
may or may not occur
[
]
possibly occur
[
]
good possibility to occur
[
]
highly likely
9.
What injuries are possible with use of this tool?
10.
How confident are you in using such a product?
1 extremely confident, use without hesitation
[
]
mostly confident
[
]
fairly confident
[
]
moderately confident
[ 1 little confident
scarcely confident
[
]
[ 1 not confident at all
[
APPENDIX B
Preliminary Experiment on Warning Sign Comprehension
of the Pictographic Warning Sign
The pilot study substantiated warning sign comprehension,
specifically of the pictographic warning sign. From literature on warning
comprehension, it was strongly recommended that all pictographic warning
signs be validated before adoption (Eastman Kodak Co., 1983; Collins et al.
1982), thus this pilot was conducted to confirm that people understood the
warning.
The pictographic warning was designed to communicate the same
warning message as conveyed in the "words only" warning. The message
in the "words only" warning read:
SHARP
BLADE
CAN CUT
WEAR
GLOVES!
Thus, the pictograph displays a blade cutting a hand (SHARP BLADE
CAN CUT), with the addition of someone putting on a glove (WEAR
GLOVES) (see Figure 12).
Procedure
Twenty-three subjects were randomly selected in the Cal State
Northridge cafeteria (13 males, and 10 females). These subjects were
shown the pictographic warning sign and were asked the following
question, "If you saw this sign on an electric saw, what would you think its
message is?" After the subject gave an answer, they were asked to rate
their confidence in interpretation from 1-7, 7= very confident.
76
77
Results
All subjects (1 00%) answered with the correct interpretation.
Variations in answers were similar to the responses, "Wear Gloves," or "You
can cut your hand, so wear gloves."
Results of the confidence ratings revealed 10 subjects responded with
the highest rating of '7,' four subjects rated a confidence of '6,' one person
gave a '5.5' rating, five gave a confidence of '5,' two gave a confidence of
'4,' and one person gave a confidence rating of '1.' The mean confidence
rating was 5.8 (M=5.8). If the rating of the individual who gave a confidence
rating of 1 was removed from the subject pool, the mean confidence rating
would be 6.0. It is conjectured that the individual did not objectively rate his
confidence, but was unsure about his answer, so moved to the opposite
pole of the rating scale and rated his confidence very low (1 =not confident
at all), instead of balancing his reasoning by the scale offered. However,
even with a mean rating of 5.8, it was reasonable to assume that people
understood the warning pictograph, and were reasonably confident of their
interpretation.
Conclusion
Results indicate that people understood the warning pictograph and
were reasonably confident of their interpretation of its message.
78
Figure 12. Pictographic warning sign tested for comprehension
If you saw this sign on an electric saw, what would you think its message is?
CAUTION I
1
2
3
4
5
6
7
not confident
very
at all
confident
APPENDIX C
Preliminary Experiment- Behavioral Task Scenario
The pilot study was conducted as a preliminary test to identify
potential problems that may occur in the experimental procedure and set
up.
The independent variable of perceived hazardousness included the
circular saw ("high" perceived hazardousness) and the jigsaw ("low"
perceived hazardousness). The independent variable of warning sign
included warnings with "words only," "pictograph only," and "pictograph and
words." A group of subjects were also given no warning, as a control.
Procedure
Subjects were told that they will be expected to use an electric saw. If
they felt uncomfortable with using the saw, they were given the opportunity
to decline participation in the study. For those who continued, they were
asked t9 imagine the following situation.
"You have a small bookcase that you sold to someone. Before the
buyer comes to pick it up, it accidentally breaks at one of the edges (show
drawing). You decide to fix it.
You go down to your garage or your toolshed. (Show the subject a
worktable setup which contains an assortment of hand tools).
Everything here is yours and at your disposal. You decide the way to
fix the bookshelf is to cut one foot off the piece of wood that is clamped
down in front of you, and then attach the two pieces together by screwing or
nailing hinges (Show subjects the hinges and diagram wood pieces
hinged together)
So you need to measure one foot off the end, cut it at that location,
take the two pieces, and hinge them.
79
80
The saw is in working order. When you are ready to use it, here is an
extension cord to plug it in."
Most subjects proceeded by first measuring the wood and drawing the
line with a pencil. Those who put on protective equipment (goggles, face
mask, gloves) did so at this time. Subjects then plugged in the saw and
attempted to use it by pressing the switch on the handle.
When subjects attempted to turn on the saw, they were told to stop.
The extension cord was not connected to an outlet, thus preventing subjects
turning on the power to the saw.
Subjects were then given a questionnaire. (See Figure 13)
Results
It should be noted that due to the nature of the pilot study, variations in
placement of the warning and background color of the warning were
investigated, thus these findings are not reliable. Nonetheless, the results
helped to identify potential patterns that may occur as a result of a reliably
controlled experimental design.
Overall Results. A total of 24 subjects participated in the pilot study:
13 were given the "low hazardousness" product and 11 were given the
"high hazardousness" product. Two subjects from each group were given
no warning sign.
Out of the 20 subjects exposed to the warnings, 12 subjects (60%)
noticed the warning, and seven (35%) actually heeded the warning.
Perceived Hazardousness. Six subjects out of the 11 subjects (55%)
exposed to a warning within the "low hazardousness" group noticed the
warning, but only four (36%) heeded the warning. Six subjects out of the
nine subjects (67%) exposed to a warning within the "high hazardousness"
group noticed the warning, but only three (33%) heeded the warning. Four
subjects in the "low hazardousness" group recalled the warning (36%) and
were all very confident they understood the warning (M=7).
81
Five subjects recalled the warning in the "high hazardousness" group
(56%) and their confidence rating was also very high (67%).
"Words Only" Warning Sign. Five subjects were exposed to the
"Words Only" design, three using the jigsaw and two using the circular saw.
Two of the three subjects who used the jigsaw complied with the warning,
the other subject noticed the warning but did not read or comply with it.
None of the subjects who used the circular saw complied with the warning,
but both remembered seeing it and recalled the message.
"Pictograph only" Warning Sign. Six subjects were exposed to the
"Pictograph only" design, four were given the jigsaw and two were given the
circular saw. None of the subjects complied with the warning. When the
subjects were shown the warning and asked what they thought the
message was, all subjects interpreted the message correctly, thus lack of
compliance was not due to the comprehensability of the warning sign.
"Pictograph and Words" Warning Sign. Nine subjects were exposed
to this warning sign, four using the jigsaw and five using the circular saw.
Two subjects who were given the jigsaw complied with the warning; one
other noticed the waring but did not continue to read or heed the warning.
The other two subjects did not notice the sign. Two of the subjects given the
circular saw complied with the warning, but it was revealed that both did not
see or notice the warning. They said in a situation such as this, "I would
normally put on gloves."
Placement. Variations of warning placement were conducted with the
jigsaw. Most subjects given the jigsaw had the warning placed on the
handle. Six out of 11 subjects saw the warning. All six were given the
warning sign on the handle of the saw. For those who did not see the
warning, suggestions to increase warning conspicuity were elicited, and
only one subject recommended placing the sign on the left side of the saw.
Two subjects were given the jigsaw with the warning on the left side of the
82
saw. Neither subject saw the warning. When suggestions were elicited,
they both recommended to place the warning on the handle. Even though
the number of subjects was small, there is no other reasonable area for
warning sign placement, thus, the warning sign was placed on the handle
of the saw.
Color. Minor variations in background color was investigated. Eight
subjects participated in this separate experiment, and all were given the
jigsaw. Initially, the background color of the signal word was yellow, with the
remaining background in white. Two subjects were exposed to this sign,
and none noticed the sign. An attempt to increase the conspicuity of the
sign was made by changing the background color of the signal word to red.
Again, two of the subjects who were exposed to the sign did not see it. The
next attempt to increase conspicuity involved changing the entire
background color to red. The next subject did not see the sign. The next
change involved using yellow as the entire background color. The next two
out of three subjects then noticed the warning. It was decided that yellow
used as the background color on all warnings. This color also corresponds
well with the intended message of "CAUTION," which has been used by
various sign systems (FMC Corp., 1985; ANSI, 1973).
Overall setup and realism. When subjects were asked about the
general setup and situation, all subjects responded that the setup was
comfortable, except for those who were left-handed (3 out of 32). For those
who were left-handed, they recommended the piece of wood be located on
the left side of the table. Other comments made in reference to the overall
setup regarded my presence during the entire experiment. A few subjects
(5 out of 32) felt that they were being watched, and thus felt uncomfortable.
Subjects also asked questions (6 out of 32) during the experimental task.
83
Conclusions
Based on the results of the pilot study, the following conclusions were
made.
1.
The handle of the jigsaw was the best location for the warning sign.
Thus to maintain consistency in warning sign placement between the two
saws, warning signs were placed on the handles of both saws.
2.
Yellow was used as the background color of all signs.
3.
My presence was minimized to increase the simulation of a realistic
environment.
(~
'
84
Figure 13. Preliminary Experiment- Behavioral task scenario Sample
Questionnaire
Date: _ __
Subject: _ __
Product: - - Sign: _ _ _ __
Sex:
( ) Male
( ) Female
Age: _ _
Occupation: _ _ _ __
What do you think the purpose of the experiment is about?
Were you really ready to use the tool?
1.
Have you worked with electric hand tools before? YIN
1a.lf so, what tools have you used?
2.
Have you used the tool, or something very similar to it before?
If no, go to question 5.
[ ] Yes
[ ) No
3.
When was the last time you used the tool?
[ ) this week
[ 1 this month
[ ) three months ago
[ 1 six months ago
[ 1 one year ago
[ ) two years ago
[ 1 over 2 years ago
4.
About how often do you use the tool?
weekly
monthly
( ) three months
[ 1 every six months
[ 1 yearly
[ 1 every two years
[ 1 every three years or more
[ 1
[ 1
5.
Have you
~the
tool used before? If so, when and where?
85
6.
How easy is it to use?
[ ] very easy, no skill or knowledge of use was required
[ ] easy, with little skill or knowledge of use
[ ] reasonably easy with some skill or knowledge of use
[ ] moderate in complexity with general skill or knowledge of use
[ ] somewhat complex, with fair knowledge or skill of use
[ ] complex with good knowledge or skill of use
[ ] very complex requiring extensive skill or knowledge of use
7.
How safe is the product to use?
[ ] extremely safe
[ ] safe
[ ] somewhat safe
[ ] moderately safe
[ ] somewhat unsafe
[ ] unsafe
[ ] extremely unsafe
8.
How likely is an injury to occur?
[ ] highly unlikely
[ ] possible, but most unlikely
[ ] probably not occur
[ ] may or may not occur
[ ] possibly occur
[ ] good possibility to occur
[ ] highly likely
9.
How serious of an injury may occur?
[ ] no injury is possible
[ ] insignificant injury may occur
[ ] small injury may occur
[ ] injury may occur, but treatable at home
[ ] injury may require immediate care at home but does not
require hospital care
injury may require emergency hospital care
possible death
10.
What injuries are possible with use of this tool?
86
11.
How confident are you in using such a product?
[ ] extremely confident, use without hesitation
[ ] mostly confident
[ ] fairly confident
[ ] moderately confident
[ ] little confident
[ ] scarcely confident
[ ] not confident at all
Realistic guestjons:
1.
Would you say this was the way you would normally do this task? YIN
a. If not, how would you do it?
2.
Would you set up the wood on the table this way? Y/N
a. If not, how would you set it up?
For instance, is the table, clamps, and wood placed in the appropriate place to
accomplish
the task? YIN
Is the room realistic enough to facilitate appropriate behavior? YIN
a. If not, how would you do it?
b. If so, is it because you haven't used the tool before?
3.
Would you have expected/or not expected this in a study? YIN
Was ntoo ar@cial? YIN
4.
Do you normally read instructions? Y/N
5.
Do you feel you would need instructions on how to use the product?
Sign use:
1.
Did you see a warning sign? Y/N
87
2.
If so, where was it?
3.
If so, what did it look like? and if there were words what did it say? (piece of paper to
draw)
a. How confident are you that you understood the message -- on a scale from 1-7
1=not confident at all, and 7=very confident
1
not confident
at all
4.
2
3
4
5
7
6
very confident
If you saw it, was it so obvious you couldn't miss it? YIN
a. Was it so obscure, you just remember seeing it, but can't remember what it said?
5.
Would you have expected to see a warning on the product? YIN
a. What would it have warned you about?
6.
Have you worn protective clothing before, such as face mask, eye goggles? YIN
If so, where and when?
7.
For those who had warning
a. Was the sign placed in a location to attract your attention? YIN
If not, where do you think is a better place?
b.
Did the sign attract your attention? YIN
If not, what suggestions can you give to increase attraction?
7.
For those who had warning and didn't heed warning
a. If you saw it, and didn't do it, why not?
b. Didn't understand the sign? YIN
c. The sign did not attract your attention? YIN
d. Situation was too out of the ordinary, too artificial?
e. Really didn't care about getting the task done the right way
f.
Too much trouble putting it on
APPENDIX D
Determination of Letter Height
Recommended for Labels and Markings on Panels
H(height of letter, in)= 0.00022D + K 1+K 2
where
D=viewing distance in inches
K 1=Correction factor for illuminationand viewing conditions
.06
.16
.16
.26
(above 1.0 fc, favorable reading conditions)
(above 1.0 fc, unfavorable reading conditions)
(below 1.0 fc, favorable reading conditions)
(below 1.0 fc, unfavorable reading conditions)
K2=correction for importance (for important items such as
emergency labels,
K2=.075; for all other conditions (K2=0)
Source: McCormick and Sanders (1982)
Based on formula of Peters and Adams, 1959 (p. 93)
88
APPENDIX E
Instructions to Subjects
You have a small bookcase. Its a bookcase that you use constantly.
One day it suddenly breaks at one of the edges. Since you use it
constantly, you decide to fix it. You go down to your garage or your
toolshed.
Everything here on this worktable is yours and at your disposal. You
decide the way to fix the bookcase is to cut 12" (1 foot) off the end of the
wood that is clamped down in front of you, and then attach the two wood
pieces with hinges, by screwing them together (show subject diagram
(Figure 14))
Again, you will need to:
1.
measure one foot (12") off the end of the piece of wood
2.
cut the wood at that location, then
3.
connect the two wood pieces with hinges by screwing them
together.
The saw is in working order. When you are ready to use it, here is
an extension cord to plug it in.
There is no right or wrong way to perform this task. I am primarily
concerned that you complete the task the way you would normally
approach it. You will not be timed. Again, I am concerned that you
perform the task the way you normally would.
Do you have any questions?
89
90
Figure 14. Diagram of hinges to be attached to wood pieces
BOOKCASE
12"
APPENDIX F
Subject Interview and Questionnaire Form
EXPERIMENTER FORM
FORMAL EXPERIMENT
Date:- - - - - - -
Subject: _ _ _ _ __
Product: _ _ _ _ __
Sign:
Step-by-step actions performed by subject.
91
92
INTERVIEW FORM
General Questions:
Age: _ __
M/F: - - Occupation: _ _ _ _ _ __
Left/Right Handed: _ _ _ __
Sign Use:
1.
Did subject heed warning? Y/N
2.
Did you see a warning?
If NO, go to Question 14
3.
If so, where was it?
4.
Rate from 1-7, how confident are you that the warning was placed
there?
2
not confident
at all
1
3
Y/N
4
5
6
7
very
confident
5.
What color was it?
6.
If you saw it, did you read it?
If NO, go to Question 13
7.
What was its message?
8.
If you read it, did you understand it?
Y/N
Y/N
93
9.
Rate from 1-7, how confident you are that you understood the warning
message?
2
1
3
5
4
not confident
at all
10.
11.
What was the danger?
0
1
2
incorrect
partially
correct
fully
correct
1
2
What caused the danger?
0
incorrect
12.
partially
correct
fully
correct
How could you avoid it?
0
incorrect
13.
6
7
very
confident
1
2
partially
correct
fully
correct
What did it look like? Be as accurate as possible. (Give subject a
piece of paper to draw the warning)
14.
Probe questions for those who DID NOT SEE or READ the warning.
a.
Why don't you think you saw or read the warning?
b.
Was it because:
Concentrated too much on the task? YIN
Sign did not attract your attention?
YIN
Situation was too artificial? YIN
You don't normally put on gloves in this type of situation? YIN
You are too familiar with the saw?
YIN
You just didn't look? YIN
c.
Truthfully tell me, if you saw and read and understood the
warning, do you think you would have put on gloves? YIN
Why?
15.
Probe questions for those who READ AND UNDERSTOOD, but did
not heed
a.
Why didn't you heed the warning?
b.
Was it because:
You felt it was unnecessary?
YIN
You are too familiar with the saw?
YIN
You just wanted to get the task done? YIN
You just forgot?
YIN
You felt the gloves wouldn't fit
YIN
You felt it would restrict your finger dexterity? YIN
16.
Probe questions for those who PUT ON GLOVES.
a.
Why did you put on the gloves?
b.
Was it because:
The sign was so obvious you couldn't miss it? Y/N
Because the gloves were just there? Y/N
Because you normally put gloves on in this type of
situation? Y/N
c.
If you were at home in this situation, would you put on
gloves? Y/N
d.
If you were at home in this situation would you take the time to
look around for them if you were at home? Y/N
*****
EXTRA QUESTION FOR THOSE WITH "WORDS + PICTURES"
What attracted your attention more, the WORDS or PICTURES?
Why?
96
QUESTIONNAIRE
Product Questions:
17.
Have you worked with electric hand tools before? YIN
1a. If so, what tools have you used?
18.
Have you used the tool, or something very similar to it before?
If no, go to question 20.
[ ] Yes
[ ) No
19.
When
[ ]
[ )
[ ]
[ ]
[ ]
[ ]
[ ]
was the last time you used the tool?
this week
this month
three months ago
six months ago
one year ago
two years ago
over 2 years ago
20.
About
[ ]
[ )
[ ]
[ ]
[ ]
[ ]
[ ]
how often do you use the tool?
weekly
monthly
every three months
every six months
yearly
every two years
every three years or more
21.
Have
you~
the tool used before? If so, when and where?
97
22.
How did you feel about its ease of use BEFORE this experiment?
[ 1 very easy, no skill or knowledge of use was required
[ 1 easy, with little skill or knowledge of use
[ 1 reasonably easy with some skill or knowledge of use
[ 1 moderate in complexity with general skill or knowledge of use
[ 1 somewhat complex, with fair knowledge or skill of use
[ 1 complex with good knowledge or skill of use
[ 1 very complex requiring extensive skill or knowledge of use
23.
How did you feel about how safe it was to use BEFORE the
experiment?
[ 1 extremely safe
[ 1 safe
[ ] somewhat safe
[ 1 moderately safe
[ ] somewhat unsafe
[ 1 unsafe
[ 1 extremely unsafe
24.
How did you feel about how likely an injury may occur BEFORE the
experiment?
[ 1 highly unlikely
[ ] possible, but most unlikely
[ ] probably not occur
[ ] may or may not occur
[ 1 possibly occur
[ 1 good possibility to occur
[ ] highly likely
25.
How did you feel about how serious of an injury may occur BEFORE
the experiment?
[ ] no injury is possible
[ 1 insignificant injury may occur
[ ] small injury may occur
[ 1 injury may occur, but treatable at home
[ 1 injury may require immediate care at home, but does not
require hospital care
1 injury may require emergency hospital care
] possible death
98
26.
What injuries are possible with use of this tool?
27.
How confident were you in using the tool BEFORE the experiment?
extremely confident, use without hesitation
[ 1 mostly confident
[ ] fairly confident
[ ] moderately confident
[ ] little confident
[ ] scarcely confident
[ 1 not confident at all, would think twice about using
[ 1
28.
How easy is it to use now that you have performed the experiment?
[ ] very easy, no skill or knowledge of use is required
[ ] easy, with little skill or knowledge of use
[ ] reasonably easy with some skill or knowledge of use
[ 1 moderate in complexity with general skill or knowledge of use
[ ] somewhat complex, with fair knowledge or skill of use
[ ] complex with good knowledge or skill of use
[ ] very complex requiring extensive skill or knowledge of use
29.
How safe is the product to use now that you have performed the
experiment?
[ ] extremely safe
[ ] safe
[ ] somewhat safe
[ ] moderately safe
[ ] somewhat unsafe
[ ] unsafe
[ ] extremely unsafe
30.
How likely is an injury to occur now that you performed the
experiment?
[ ] highly unlikely
[ ] possible, but most unlikely
[ ] probably not occur
[ ]
may or may not occur
[ ] possibly occur
[ ] good possibility to occur
[ ] highly likely
99
31.
How serious of an injury may occur now that you performed the
experiment?
[ ] no injury is possible
[ ] insignificant injury may occur
[ ] small injury may occur
[ ] injury may occur, but treatable at home
[ ] injury may require immediate care at home, but does not
require hospital care
injury may require emergency hospital care
possible death
32.
How confident are you in using the tool now that you performed the
experiment?
[ ] extremely confident, use without hesitation
[ ] mostly confident
[ ] fairly confident
[ ] moderately confident
[ ] little confident
[ ] scarcely confident
[ ] not confident at all
33.
Have you ever been injured using a tool (eyes, hands?) Y/N
If so, what happened in the situation?
34.
Do you know of anyone who was injured using this tool?
If so, what happened in the situation?
35.
Have you worn protective clothing before, such as face mask, eye
goggles? Y/N
If so, where and when?
Y/N
Realistic questions:
36.
Would you say this was the way you would normally do this task? YIN
If not, how would you do it?
100
37.
Is the worktable comfortably set up to accomplish the task?
If not, how would you set it up?
38.
Was there anything in the experiment you would not normally do?
Y/N
If so, what was it?
39.
Do you normally read instructions? Y/N
40.
Did you feel the warning was reasonable? ·Y/N
Why? _________________________________________
APPENDIX G
Experimental Data
Perceived Hazardousness
Jigsaw
Dependent
Variables
Words
Only
c
Pictograph
Only
0>
U5
Circular Saw
Proportions and Percentages of
Total Subjects
noticed
read
complied
recall danger
recall cause
recall avoidance
12/16
6/16
2/16
2/16
4/16
4/16
75%
37.5%
12.5%
12.5%
25%
25%
13/16
9/16
7/16
5/16
7/16
7/16
81.25%
56.25%
43.75%
31.25%
43.75%
43.75%
noticed
read
complied
recall danger
recall cause
recall avoidance
7/16
2/16
2/16
2/16
1/16
1/16
43.75%
12.5%
12.5%
12.5%
6.25%
6.25%
10/18
7/18
4/18
5/18
2/18
5/18
55.6%
38.9%
22.2%
27.8%
11.1%
27.8%
noticed
read
complied
recall danger
recall cause
recall avoidance
7/16
3/16
2/16
3/16
1/16
2/16
43.75%
18.75%
12.5%
18.75%
6.25%
12.5%
8/16
11/16
8/16
5/16
8/16
9/16
50%
68.75%
50%
31.25%
50%
56.25%
0/17
0%
0/16
0%
-0>
o .S
Q) c
c..'>-Ctl
~---~ Words+
Pictograph
No
Warning
complied
101
102
APPENDIX G
(Continued)
Perceived Hazardousness
Circular Saw
Jigsaw
Recall Proportions and Percentages of
Recall Data Only
Scores
Danger
Words
Only
Cause
Avoidance
Danger
c
0>
U5
0 g> Pictograph
Q)
.E
o.ro
Cause
Only
~~
Avoidance
Danger
Words+
Pictograph
Cause
Avoidance
0
1
2
0
1
2
0
1
2
4/16
0
1
2
0
1
2
0
1
2
1116
0
1
2
0
1
2
0
1
2
2/16
2/16
4/16
2/16
4/16
2/16
2/16
1/16
2/16
1/16
1/16
2/16
2/16
1/16
1/16
2/16
25%
0%
12.5%
12.5%
0%
25%
12/5%
0%
25%
6.25%
0%
12.5%
12.5%
6.25%
0%
12.5%
0%
6.25%
0%
6.25%
12.5%
12.5%
0%
6.25%
6.25%
0%
12.5%
4/16
5/16
2/16
7/16
~/1
b
7/16
1/18
1/18
4/18
4/H~
2/18
1 f11j
5/18
6/16
5/16
3/16
1/16
7/16
2/16
9/16
25%
0%
31.25%
12.5%
0%
43.75%
12.5%
0%
43.75%
5.55%
5.55%
22.2%
22.2%
0%
11.1%
5.55%
0%
27.8%
37.5%
0%
31.25%
18.75%
6.25%
43.75%
12.5%
0%
56.25%
APPENDIX H
lntercorrelation Matrix
of Product Perceptions
Q)
Q)
0
Q)
"0
U)
::l
Q)
.D
0
.D
Q)
.D
U)
~
.D
::l
~
:£ :£
.u
c:
::l
Q)
c:
.E
Q)
~
~
0
Qj
.D
0
.D
Q)
3:
0
J:
-1
~
Qj
.:t::
iii
ro
~
Qj
U)
Q)
E
Last time used
0
Q)
"0
Q)
Q)
Qj
0
Q)
ro
(f)
U)
ro
L.U
~
::l
::l
U)
>
Qi
.::£
::J
::l
0
-~
(f)
Qj
Q)
(])
]2
'E
0
()
0
·;::
Q)
(f)
X
>
Qi
.::£
::J
t
~
Q)
U)
l1l
L.U
t
~
Q)
ro
(f)
~
::l
·c>
Qi
.::£
::J
~
ro
~
::l
:£
~
ro
t
.:t::
::l
Q)
·;::
u
c:
U)
(])
::l
"0
0
·;::
Q)
(f)
U)
l1l
~
0
()
0
(])
(f)
X
>
Qi
~
-1
1
How often used
.773
Ease before
1
.152 .186
1
Safe before
-.124 -.26 .544
Likely injury before
.026 .142 .042 .221
1
1
Serious injury before -.338 -.321 -.072 .208 .511
1
Confidence before
.521 .353 .607 .424 .275 -.001
LikelyxSerious
before
-.13 -.043 -.048 .203 .855 .857 .164
Ease after
.43
Safe after
-.032 .001 .215 .416 .435 .15
Likely injury after
.418 .461 -.245 -.275 .238 .053 .077
Serious injury after
Confidence after
LikelyxSerious
after
-.11
1
.503 .702 .253 .067 -.012 .757
.529
1
.267 1
.377 .463
1
.288 .26
.234
1
.113 -.114 -.373 .309 .501 -.031 .521 .256 .163 .553
1
.507 .395 .632 .282 .337 .204 .832
.331 .844 .407 .317 .341
.308 .406 -.237 -.343 .263 .198 .036
.383 .267 .182 .97
103
1
.719 .344 1