Method of evaluating metal textures
by the sound symbolism of onomatopoeia
Junya Yoshino†
Akira Yakata‡
Yuichiro Shimizu†
Masaharu Haginoya∗
†
Graduate School of Informatics and Engineering,
The University of Electro-Communications
‡
Faculty of Electro-Communications,
The University of Electro-Communications
∗
Calsonic Kansei Corporation
[email protected]
Abstract
In recent years many products, including many
electric appliances, are starting to be made of imitation metals, which are lighter in weight and
lower in cost than real metals. However, imitation metals can sometimes look and feel cheaper.
This study proposes that differences in mimetic and onomatopoeia associated with imitation
and real metals can be used in metal texture design to make imitation materials look and feel
more like real materials. Japanese is a language known to have a large number of mimetic
and onomatopoeia for expressing textures. For
example, such words expressing a sense of smoothness often use the consonant /s/ in their
first syllable, as in “sara-sara”. We conducted psychological experiments where participants
were asked to look at a pair of imitation and real materials without touching them and respond
with onomatopoeia that they felt were associated
with them. Participants responded significantly more onomatopetic words for real materials than for imitation materials. Furthermore, we
analyzed ono-matopoeia obtained from both real
metals and imitation metals using a system that
quantifies the phonological information of onomatopoeia. A comparison of the onomatopoeia
evoked by real metals and those evoked by imitation metals revealed differences in the affective
features of the two types of metals.
Keywords: Metal Texture Design, Real Metal,
Imitation, Onomatopoeia
1 Introduction
In recent years, many products, including electric appliances and car interiors, are increasingly
made of imitation metals, which are lighter in
weight and lower in cost than real metals. While
Maki Sakamoto†
at first glance imitation metals may appear similar to real metals, they can sometimes look and
feel cheaper. In product development, the field
of metal texture design aims to make imitation
metals look as similar to real metals as possible. However, the reason why imitation materials often feel different from real metals even
if given the same texture design remains a mystery, and it is still unclear what kinds of design
are effective to make such textures more realistic. Humans can infer the properties of materials
through the five senses; namely, vision, touch,
smell, taste, and hearing. The present paper focuses on vision. Many studies have investigated
how humans interpret visual input to, for example, estimate the properties of surfaces, how to
differentiate peaches and nectarines, or how to
tell the difference between unfinished and polished wood [1] , [2]. There are many visual attributes that help us to distinguish different surface materials, such as lightness, color, and texture. For example, [1] pointed out that one of the
basic characteristics of image statistics, surface
perception —the distribution of luminance values in an image, or the “skew”—is highly correlated with subjective judgments of gloss and
lightness.
However, while such findings reported by previous studies have focused mainly on material
perceptions through experiments using pictures,
there is still little research on the emotional or
sensuous perceptions of texture. [3] was one
such study that focused on the emotional perception of metal textures in an attempt to analyze
the features of human texture perception. However, the stimuli used in their experiment were,
nonetheless, images of textures.
To pursue a new method of capturing the emotional and sensuous aspects of material per-
ception, this study focuses on onomatopoeia as
sound expressions that can symbolize various
textures. The existence of synesthetic associations between sounds and sensory experiences,
known as sound symbolism, has been demonstrated [4], [5]. It is also known that a sensorysound correspondence can be found not only
in words referring to visual shapes, such as in
the examples “mal/mil” and “buba/kiki” for describing round and sharp shapes, respectively, as
noted in the landmark studies of [5] and [6], but
also in words referring to tactile, smell, and taste
sensations [7], [8] . Japanese is known to have a
large number of onomatopoeia; for example, [9]
describes the sound symbolic associations between the phonemes of Japanese onomatopoeia
and their particular meanings, as shown in Table
1.
[8], [10] investigated the sound symbolic associations between the phonemes of Japanese onomatopoeia for expressing tactile sensations and
the subjective evaluations of comfort/discomfort
for touched objects. For example, onomatopoeia
ex-pressing a sense of smoothness often use the
consonant /s/ in their first syllable, as in “sarasara” while those expressing roughness often
use /z/ in their first syllable, as in “zara-zara”
However, no study has attempted to use onomatopoeia to explore visual differences between
real and imitative materials with similar texture
designs. The purpose of this study is therefore
to investigate the effectiveness of onomatopoeia
in the visual measurement of metal textures and
explore the possibility that differences in the
onomatopoeia associated with imitation and real metals can be used for metal texture design
with the aim of making imitation materials look
and feel more like real materials.
A previous study by [11] on the texture of lacquer found that expert participants evaluated the
characteristics of materials more accurately than
non-experts. Therefore, we first chose 20 experts
to be participants in our experiment; specifically, they were 18 men and two women who had
worked for over 5 years in professions dealing
with metal surface design. Then we chose 30
non-experts (18 men and 12 women ) to comprise a comparison group. The experiment was
per-formed using a box set up with a light color
temperature of 5500 K, and in which a pair of real and imitation metals was placed, as shown in
Figure 1.
Figure 1. Experimental setup
The experimental stimuli were 15 pairs of real metals and imitation metal-like materials with
the same surface texture designs shown in Figure 2. In Figure 2, the material shown in the
right side of each image is the imitation, and the
material on the left side is the real metal. However, the placement of the materials was randomized for each participant. The experimental stimuli were made by Calsonic Kansei Corporation,
Saitama prefecture, Japan.
2 Experiment
2.1 Materials and design
In this experiment, we aimed to compare the
numbers and types of onomatopoeia associated
with real metals with those associated with imitation metals. [8], [10] notes that onomatopoeia
is effective in understanding the sensibilities of
human texture perception, such as likes or dislikes and comfort or discomfort; thus we hypothesize that real metals are more easily associated with onomatopoeia than metal-like materials,
namely imitation metals.
Figure 2. Examples of experimental stimuli
Table 1. Examples of sound symbolic associations between Japanese phonemes and meanings
/i/
/a/
Vowel
line, extended in a straight line
flat, spreading, large surface
2.2 Procedure
Participants were given instructions on the procedure and a brief description of onomatopoeia,
along with some examples of Japanese onomatopoeic expressions that are typically used to
describe things other than metal (so there would
be no influence on the actual experiment). Participants were asked to sit in front of the box with
their forehead placed on the board attached to the
top of the box, as shown in Figure 3. Then, they
were asked to observe a pair of objects consisting of one real metal and one imitation metal-like
material, and then provide as many onomatopoeic expressions they could associate with the objects as they could during a 20-second period of
response time. The participants were instructed
not to touch the materials, because touching can
reveal non-visual differences between real and
imitation metals.
Figure 3. Image of experimental trial
2.3 Results
The average number of onomatopoeia obtained
in response to the real metal stimuli was 1.50
(1.36 from the experts and 1.59 from the nonexperts), while the average number of onomatopoeia obtained in response to the imitation
metal stimuli was 1.07 (0.94 from the experts
and 1.16 from the non-experts). We conducted
a t-test (two-tailed, 5% confidence level) to ex-
/h/
/s/
Consonant
softness, weakness
smoothness, serenity, tranquility
amine whether there was a significant difference
between the average numbers of onomatopoeia
for the real metals and the imitations.
A two-tailed t-test (both sides, 5% confidence
level) revealed a significant difference between
the two averages: t(49)=8.87, p < .01 (total),
t(19)=6.61, p < .01 (experts) and t(29)=6.28,
p < .01 (non-experts). This result suggests
that real metals were more easily associated with
onomatopoeia than imitation metal-like materials. This result further suggests that even if two
objects have the same surface design, real metals
are more easily associated with emotional texture perceptions and thereby more easily evoke
a variety of onomatopoeia, which are presumed
to be directly associated with both intuitive and
emotional perception.
Furthermore, we compared the types of onomatopoeia obtained from the non-experts with
those obtained from the experts. We regarded
the word given most frequently by each group
of participants to describe each material as the
representative word for the material for that
group. Table 2 shows the representative onomatopoeia obtained for each material. Tactile
onomatopoeia such as “zara-zara” (describing a
rough texture) were obtained from non-experts
more than from experts, while experts responded
with more visual-oriented onomatopoeia such as
“teka-teka”, which expresses brightness. Therefore, we conducted a statistical analysis to determine whether tactile onomatopoeia were more
frequently provided by non-experts than experts. Results of the analysis showed that tactile
onomatopoeia were provided by non-experts significantly more frequently than by experts: χ
2(1,N=75)=16.835, p < .01. This result suggests that while metal texture design experts tend to
focus on the visual design or qualities of metal surfaces, non-experts —that is, lay persons
—tend to perceive material properties through
experiences closer to the sense of touch rather
than vision.
Table 2. Representative onomatopoeia associated with each material for each participant type
Design
1
2
Non-experts
real metal imitation
zara-zara tsuru-tsuru
boko-boko
tsuru-tsuru
Experts
real metal imitation
une-une
sara-sara
gira-gira
teka-teka
kira-kira
sara-sara
gira-gira
3 Analysis by New Evaluation Method
3.1 Method overview
We analyzed the information expressed by the
onomatopoeia given in Table 2 using a method
that estimates the texture feelings expressed by
onomatopoeia based on their phonological characteristics. We designed an onomatopoeic image
estimation model that quantifies images evoked
by onomatopoeia by calculating a linear sum of
the phoneme evocations (i.e., perceptions) using
the following equation (1).
Ŷ = X1 + X2 + · · · + X12 + X13 + Const. (1)
Here, Ŷ represents the estimation of perceptions of 43 measurement scales for a given onomatopoeia. X1-X13 represent the perceptions of
the respective phonemes, and Const. represents
constant terms. To obtain the phoneme perception data, we applied the onomatopoeia image
data from our experiment to our model, and calculated the perceptions of each phoneme using a
class I mathematical quantification theory. This
theory is a kind of multiple regression analysis
using the dummy variable.
We conducted a psychological experiment to
create the phoneme perception data. Participants
were asked to evaluate their subjective impressions of 312 onomatopoeia (six groups of 52
words) against 43 pairs of adjectives in 7-point
semantic differential (SD) scales. Onomatopoeic stimuli were randomly displayed on a computer screen for each participant as shown in Figure
4. In total, 78 Japanese undergraduates aged 20
to 24 (51 males and 27 females, divided into six
groups of 13) participated in the experiment.
Results of the experiment included 174,408 evaluations (312 words × 43 scales × 13 participants). We then calculated the average evaluated values for the onomatopoeic perception data
Figure 4. Image of experimental trial
across the participants (312 words × 43 scales).
We then applied the onomatopoeic perception
data to our model and calculated the perception
values of each phoneme by making use of a class
I mathematical quantification theory.
For example, the expression “fuwa-fuwa”
made by repeating /fuwa/, is composed of the
first syllable /fu/ (/f/ + /u/) and the second syllable /wa/ (/w/ + /a/). Therefore, the image of
“fuwa-fuwa” for the “hard/soft” scale is estimated by the following equation. Because the evaluated values are based on 7-points scales, the estimated value 6.28 suggests that “fuwa-fuwa” is
strongly associated with an image of softness.
Ŷ
= /h/ + /u/ + /w/ + /a/
+repetition + Const.
= 0.29 + 0.55 + 0.71 + 0.07
+0.23 + 4.43
= 6.28
To evaluate the accuracy of our model, we
compared the perception values estimated by our
model with the real values for the 312 onomatopoeic stimuli obtained from our participants
in experiment. (Hereafter, we refer to the former as “estimated values” and the latter as “real
values”.) We calculated the multiple correlation
coefficients between the estimated values and the
real values for the 43 scales. Results showed that
for 33 scales, the multiple correlation coefficient
values were in the range of 0.8 to 0.9, while for
the other 10 scales the values were 0.9 or higher.
We thus considered our model sufficiently valid
for estimating human onomatopoeic perceptions.
and the newly created imitation sample (placed
on the opposite side not occupied by the original imitation), as shown in Figure 5. Participants
were asked to answer which object on the sides
seemed closer to the real metal object in the middle. We conducted this procedure for imitations
with depths of 0.2 mm, 0.4 mm, and 0.6 mm.
3.2 Analysis results
Using our method, we calculated the information
expressed by onomatopoeia words such as those
shown in Table 2, all of which were obtained in
the psychological experiments described in Section 2 for the 43 scales. Table 3 shows examples
of the output by our method.
We analyzed the difference between the evaluation values of onomatopoeia words obtained
from real metals and imitations of each design included in the experiment. We calculated the absolute value of each scale and found
that texture perceptions between the real metals
and their imitations were the most different for
the following evaluation scales: [smooth/rough],
[heavy/light], [clean/dirty], and [wet/dry].
3.3 Second Evaluative Experiment
Because our findings revealed that one of the
most different scales between the real and imitation metal perceptions was [smooth/rough], we
conducted another experiment focusing on Design 6, which had been evaluated differently on
the scale of [smooth/rough]. Our method had
estimated that humans would evaluate the real
metal as being rougher than the imitation, even
when the texture design was the same. Namely,
Design 6 features geometrical pattern of 0.2 mm in depth for both the real and imitation metal
stimuli. Therefore, to make the imitation metal
stimulus look more similar to the real metal stimulus, we increased the roughness of the imitation
metal by increasing the depths of the geometrical
pattern to 0.6 mm and 0.4 mm. (The design itself
was created by Calsonic Kansei Corporation.)
We conducted an experiment using the real
Design 6 metal and the newly created, rougher
imitation metal. The procedure of the experiment was the same as that described in Section 2.2. Participants were asked to sit in front of the box with their forehead placed on the
board attached to the top of the box, and asked
to compare among a sample of the real metal (placed in the middle), the original imitation
sample (placed to either the right or left side),
Figure 5. Image of experimental trial
3.4
Evaluation results
Results showed that all participants responded
that the new metal-like material with a depth of
0.6 mm seemed most similar to the real metal.
This result indicates that by comparing results of
the experimental outputs between onomatopoeia
associated with real metals and those with metallike materials, we can better understand how to
create imitation metals to look more like real
metals by modifying their texture design as indicated by the experimental analysis.
4
Conclusion
This study suggests that differences in onomatopoeia associated with real and imitation
metals can be used in metal texture design to create imitation materials that look and feel more
like real materials. Through psychological experiments in which participants were asked to
visually evaluate a pair of imitation and real materials without touching them and respond with
onomatopoeia associated with such materials,
we showed that real materials were significantly
more easily associated with more onomatopoeia
than were imitation materials. This result indicates that even if imitation metals have similar surface designs as real metals, real metals
are still more easily associated with emotional
Table 3. Examples of output from our system
Non-experts（style 1） Real metal(R)
scales（1 ←:→ 7）
zara-zara
warm：cold
4.76
wet: dry
5.15
smooth：rough
4.90
texture perceptions and as such more easily evoke onomatopoeia, which have been found to
be directly associated with intuitive and emotional perception. This finding suggests that such
differences in onomatopoeia associated with imitation and real metals can be used to inform
metal texture design to make imitation materials
look and feel more like real materials, while also
providing useful insights to metal texture design
experts.
Furthermore, we analyzed onomatopoeia obtained from responses to observing real and
imitation metals using a method that quantifies onomatopoeic phonetic (phoneme) information. A comparison of outputs between the onomatopoeia evoked in response to real metals and
those evoked in response to imitation metals revealed a difference in the affective features of the
two types of metals. Based on these differences,
we created new metal-like materials. After testing these new materials, we confirmed that we
succeeded in making metal-like materials that
were perceived as being more similar to their real
metal counterparts.
In our future work, we plan to apply this
method to various other materials, such as pearl,
glass, and stone.
Acknowledgment
This work was supported by Grant-in-Aid for
Scientific Research on Innovative Areas ”Shitsukan” (No. 23135510) from MEXT, Japan
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