Subliminal influencing in
advertising: does it work?
Eva Van den Bussche, Gigliola Brintazzoli, Natacha Deroost
& Eric Soetens
Colloquium 16-06-2011
6/23/2011
Herhaling titel van presentatie
1
Overview
• Can subliminal information influence
our behavior…
• …in an experimental context? (PART I)
• …in a more real-life/advertising
context? (PART II)
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Part I
Can subliminal information
influence our behavior in an
experimental context?
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Overview Part I
•
•
•
•
•
Early demonstrations
Masked priming paradigm
Prime awareness
Meta-analysis
Conclusion
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Early demonstrations
• Can subliminally presented information
influence our behaviour?
- Controversial
- Long history
- Subliminal = ideas below the “limen” or
threshold for consciousness (Herbart, 17761841)
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Early demonstrations
• First empirical studies:
1. Peirce & Jastrow (1884):
Conclusion: even when
to be
Wich claiming Wich
Pressure 1
Pressure 2
pressure
pressure
unaware of any difference
(score=0),
was the
was the
subjects could still strongest?
discriminatestrongest?
the two
pressures above chance
0
1
2 level!
3
P1
P2
“No preference, nonsensical answer”
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forced-choice
discrimination
task
Early demonstrations
2. Sidis (1898):
5 S
Digit or
letter?
Conclusion: even when claiming seeing
only a dim, blurred spot, subjects could
discriminate letters and digits AND
identify them above chance level!
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Masked priming paradigm
• Can subliminally presented information
influence our behaviour?
- Subliminal perception = a stimulus is
demonstrated to be invisible while still
influencing thoughts, feelings, actions,
learning or memory (Kouider & Dehaene,
2007)
- How do we measure subliminal perception
today?
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Masked priming paradigm
Masked priming paradigm (Marcel,
1983)
9
##
17ms
6
33ms
480ms
##
Smaller than 5
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Larger than 5
Masked priming paradigm
Congruent
condition
Incongruent
condition
Prime
6
1
Target
9
9
Difference
(RT_I - RT_C)
= priming effect
Both > 5
Faster RTs
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One <, one > 5
Slower RTs
Masked priming paradigm
• 1983: Masked priming paradigm (Marcel)
• 1986: Criticism (Holender) are we really
measuring subliminal/unconscious
perception? Inadequate measures of prime
awareness!
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Prime awareness
• Prime awareness assessment:
1. Subjective threshold self-report (e.g.:
“Were you aware of the prime”)
2. Objective threshold discriminative
abilities post-hoc post-test
–
–
–
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Identification: identify the prime
Forced choice absent/present: was there a prime?
Forced choice categorization: classify the prime
Prime awareness
• How “fast” will a method conclude that
the primes were unconscious?
1. Subjective report
2. Prime identification
3. Forced choice absent/present, forced choice
categorization
Preferred! If a priming effect is observed
AND the primes could not be perceived
above chance, most strict evidence of
truly unconscious/subliminal priming!
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Meta-analysis
(Van den Bussche et al., 2009, Psych Bull)
• Mid-1990s: methodological improvements
(Dehaene, Greenwald) more reliable
masked priming paradigms
• From then on: numerous experimental
studies using the masked priming paradigm
Statistically combine published and
unpublished data using meta-analytic
techniques
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Meta-analysis
(Van den Bussche et al., 2009, Psych Bull)
• Search criteria: Published between 1983 – 2006 in
English, Dutch, French or German
• Search string: (SEMANTIC OR ASSOCIATIVE) AND
(PRIMING OR PRIME) AND (MASKED OR
SUBLIMINAL OR UNCONSCIOUS OR AUTOMATIC)
• Four databases were searched (WoS, ScienceDirect,
PubMed, PsycInfo)
• Cross-references, reviews, experts
• 749 published articles were selected
• Two reviewers coded these articles using 7 criteria
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Meta-analysis
•
(Van den Bussche et al., 2009, Psych Bull)
Inclusion criteria:
1. Prime-target relation of a semantic nature in the
visual domain (e.g. cat - dog)
2. Primes had to be presented subliminally
3. Semantic categorization, lexical decision or naming
task
4. Standard priming procedure
5. Centrally presented single word or symbol primes
6. Healthy sample and N>1
7. Sufficient statistical information to compute an effect
size
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Meta-analysis
(Van den Bussche et al., 2009, Psych Bull)
•
46 published and 8 unpublished studies
containing 156 separate conditions
•
Effect sizes were computed:
RT (unrelated trials) – RT (related trials)
ES =
SD
–
–
ES = 0: no effect
ES > 0: positive ES (~ priming effect)
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Meta-analysis
•
Effect sizes:
3,5
Effect Sizes
2,5
1,5
0,5
-0,5
-1,5
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(Van den Bussche et al., 2009, Psych Bull)
Overall mean ES = 0.80 (CI: 0.60-1.00)
Conclusion Part I
•
•
Strong and robust subliminal priming
effects across the experimental
literature
Subliminal information can influence
our behavior… in an experimental
context!
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Part II
Can subliminal information
influence our behavior in an
real-life/advertising context?
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Overview Part II
•
•
•
•
•
•
Early demonstration
People’s perception
Time-course of subliminal priming
Subliminal priming applied
Our approach
Conclusions
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Early demonstrations
• Vicary (1957): subliminal messages
“drink coca-cola”, “eat popcorn” increased product sales
• Enormous impact on public opinion:
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Early demonstrations
• Subliminal advertising was banned in
many countries
• Vicary had falsified data
• Impact on public remained
• Subliminal advertising is still being
used today McDonald’s
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People’s perception
• Consumers:
- are familiar with subliminal advertising (7481%)
- believe it is being used (68-81%)
- believe it “works” (72%)
• Significant positive correlation with
education
Zanot et al., 1983; Synodinos, 1988; Rogers & Smith, 1993
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People’s perception
• Our study (in prep):
- N=99, psychology students, mean age =
18.7, 89% female
- Participants received definition of
experimental subliminal perception
- 6 questions assessing their perception on
these kinds of effects in a daily life and
advertising situation
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People’s perception
• Our study (in prep):
1.
2.
3.
4.
5.
Unconscious influencing (UI) is present in daily life: 99%
People in general are susceptible to UI in daily life: 92%
I am susceptible to UI in daily life: 91%
UI is is being used in advertising: 95%
People in general are susceptible to UI in advertising:
82%
6. I am susceptible to UI in advertising: 68%
Difference between men (27%) and women (73%)
(p= .002)!
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People’s perception
• Actual application of unconscious
advertising:
- Rogers & Seiler (1994) questioned 256
American advertising companies about
whether they had ever used UI
- 91% NO, 8% did not understand the
concept of UI correctly, only 1 firm had
used it “as a prank”
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People’s perception
• Conclusion:
• People are familiar with subliminal
advertising, they believe it is being
used and they believe it works
• BUT: companies are not using it
Discrepancy between the perception
of people and the actual use!
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Time-course of subliminal priming
• Still the question remains: does it
work?
• Generalizing findings made in an exp
context to a more real-life situation is
problematic time-course of
subliminal priming
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Time-course of subliminal priming
Masked priming paradigm
9
6
33ms
480ms
##
Smaller than 5
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SOA =
50ms
##
17ms
Larger than 5
Time-course of subliminal priming
• Exp context: subliminal info (prime) and
behavior undergoing the influence of it
(response to target) follow each other very
closely in time
prime exerts its influence almost
immediately
• Meta-analysis: average SOA = 128ms (max
= 784ms)
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Time-course of subliminal priming
• Subliminal priming is short-lived!
• Priming drops to a non-significant value
within a few hundreds of milliseconds (Forster &
Davis, 1984; Greenwald et al., 1996; Ferrand, 1996)
Casts serious doubt on its effectiveness in
everyday life and advertising
Subliminal info (an ad) and the behavior
undergoing the influence of this info (buying
the product) are much farther apart
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Time-course of subliminal priming
Pratkanis, 1992
Trappey, 1996
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Subliminal priming applied
• Still, some studies have successfully applied
subliminal priming in more real-life contexts
• Karremans et al. (2006):
- Subliminally primed with “Lipton Ice” or “Npeic
Tol” (23ms + masked)
- Questions:
- If you were offered a drink now, what would you prefer (Lipton
Ice or Spa Rood)
- If you would sit on a terrace now, how likely is it that you
would order Lipton Ice/Coca Cola/Spa Rood (scale 1-7)
- I would like to drink Lipton Ice/Coca Cola/Spa Rood at this
moment (scale 1-7)
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Subliminal priming applied
• Karremans et al. (2006):
- Increased choice for, and intention to, drink
Lipton Ice, but only for thirsty participants
- See also Strahan et al., 2002; Bermeitinger et al., 2009
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Subliminal priming applied
• Consumer choices can be influenced by
subliminal primes that could help fulfill a
need, but only if the consumer is already
deprived!
- Veltkamp et al. (2011): even when no deprivation
is present, subliminal conditioning can motivate
consumers as if they were deprived
- Verwijmeren et al. (in press): subliminally priming
an habitual brand has no effect, and a primed
brand can lead to increased choice even at the
expense of an habitual brand
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Subliminal priming applied
• Can we conclude that subliminal influencing
in a real-life/advertising situation works?
• Let’s not jump to conclusions just yet…
• Methodological issues:
- Prime awareness assessment
- Time-course: prime and target still very close in
time, laboratory context
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Our approach
• Aim: examine whether subliminal influencing
can be effectively and reliably implemented
in more everyday life and advertising
situations, using strict methodology
• New studies:
1. A replication of Karremans et al. (2006)
2. A brand study
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1. A replication
• First aim: replicate Karremans et al.’s (2006)
study
• Method: Identical replication, except:
- We assessed level of thirst at t0 and t1
- We used a more strict prime awareness assessment
(i.e. categorize subliminal primes as word or nonword)
- Same subjects participated in actual experiment AND
post-hoc prime awareness test
- N = 28
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1. A replication
• Results:
- Prime awareness: 43% subliminal!
- No differences between “Lipton Ice” group and
control group with regards to choice for and
intention to, drink Lipton Ice
- No differences between thirsty and non-thirsty
subjects
- BUT: “Lipton Ice” group showed a significant
increase in thirst (p = .007), compared to the
control group (p = .11)
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1. A replication
• Why were we unable to replicate Karremans
et al. (2006)?
- Power?
- Difference in prime visibility?
- Role of habits: 50% of our participants
indicated Lipton Ice as their favorite brand (cf.
Verwijmeren et al.)
- Can subliminal priming induce a deprivation?
Requires further investigation!
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2. A brand study
(Brintazzoli et al., in prep)
• Idea = back to basics!
• Design an experiment very similar to a
typical masked priming study
• BUT: with more real-life stimulus
material
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2. A brand study
(Brintazzoli et al., in prep)
• Stimuli
•
•
•
•
•
Typical masked priming experiment
Primes = 10 very familiar brand logos selected in a pilot study
Targets = letter strings
Task: decide as fast as possible whether the
target is a word (or brand name) or a
nonsensical non-word
2 versions: conscious (17ms) or unconscious
(13ms)
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2. A brand study
(Brintazzoli et al., in prep)
• 5 conditions
a)
b)
c)
d)
e)
related brand:
- MCDONALD’S
unrelated brand:
- LACOSTE
related non-brand:
- HAMBURGER
unrelated non-brand:
- CAR
non-word:
- NOOLWEF
400 trials (50% word and 50% non-word)
Only 200 word trials were analyzed
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Design:
Pag.45
2. A brand study
(Brintazzoli et al., in prep)
• Prime visibility
•
•
Objective forced choice categorization test
Conscious version (N=29):
-
Subjects correctly categorized 75% of the primes
d’ =1.56, t(38)= 9.43, p< .001
Unconscious version (N=19):
•
-
Subjects correctly categorized 52% of the primes
d’ = 0.19, t(18)= 2.28, p= .035, no correlation with
priming
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2. A brand study
(Brintazzoli et al., in prep)
• Results
550
540
**
RT (ms)
530
**
520
510
related
unrelated
500
490
480
brand
non-brand
conscious
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brand
non-brand
unconscious
2. A brand study
(Brintazzoli et al., in prep)
• Discussion
•
•
•
Brand logos possess the power to prime
their brand names and, remarkably, words
associated to the brand
primes “McDonald's”, but also
“hamburger”!
However, this only occurred when they were
presented above the consciousness
threshold!
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Conclusion Part II
•
•
•
•
•
Real-life primes only elicited priming when they
were presented consciously
BUT: what do we define as “conscious”
and “subliminal”???
Exp context: strict methodology to assure
prime invisibility required!
Is there a consensus in this more applied field?
Is it the same as in the exp field? Should it be?
What are we studying? What do we want to
study?
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Conclusion Part II
• Future studies:
1. More laboratory/experimental studies:
-
Focus on strict design: compare “conscious”
versus “unconscious”
Different stimulus material, tasks,…
Influence on decision-making, choice behavior
Still only short-lived effects longevity of
subliminal priming?
2. What about field studies?
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Conclusion
• Can subliminal information influence
our behavior…
• …in an experimental context? YES!
• …in a more real-life/advertising
context? ???
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Contact
Eva Van den Bussche
Vrije Universiteit Brussel
Department of Psychology
Pleinlaan 2
1050 Brussels
Belgium
[email protected]
http://homepages.vub.ac.be/~evdbussc//
SCAN Utrecht
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