Developing preference to subthreshold visual patterns estimated by pupil response. Tatsuto Takeuchi , Sanae Yoshimoto 1

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1, 2, 3

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, Aya Shirama , Stephen W. Lo , Hisato Imai 2, 3

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4

4

5

5

Japan Women’s Univ., NTT CS Labs., JST CREST, Univ. of Calgary, Tokyo Woman’s Cristian Univ.

RESULT 2: Pupil response during subliminal mere exposure

INTRODUCTION Subliminal mere exposure effect (SMEE) is a psychological phenomenon where people tend to prefer patterns to which they are subliminally exposed to many times, even when they cannot recognize the patterns they have observed. Perceptual fluency hypothesis states that decreasing mental effort invested on processing patterns is a key factor of inducing SMEE. Since it is known that pupil response reflects mental effort (Kahneman & Beatty, 1966), the close relationship between pupil response and the strength of SMEE is predicted.

The pupil size during subliminal exposure was significantly smaller for the participants who exhibited the SMEE. Similar relationship was found within each participant who showed the different tendency between Bengal characters and line drawings, such as showing the SMEE for characters but not for line drawings. Between participants

Within participant

SMEE observed SMEE NOT ebserved

QUESTION 1: How is pupil response related to SMEE? QUESTION 2: What is the time course of SMEE? METHOD Thesize pupilofsize We PREDICTION: measured pupil the will participants while they were exposedwhen to subthreshold subliminal patterns such constrict the subjects as line drawings or characters. exhibit the preference to Each the visual pattern was presented 8 msec followed by a random-noise mask visual for patterns subliminally pattern of 492 msec. After the presentation, participants presented. judged their preference to the patterns by a 2AFC task and a likeability rating. We also run a supraliminal condition, in which the presentation duration of the visual pattern was 433 msec.

Fig 4. The normalized pupil size during subliminal mere exposure as a function of the number of exposures. Left: the result of between participants. Right: the result of within participant.

RESULT 3: Pupil response during likeability rating During the early phase of the experimental session, there was no sign of correlation between pupil size and likeability rating for both type of participants, those who showed and didn’t show SMEE. However, at the late phase of the session, the pupil size was smaller when the likeability rating was higher for the participants who showed the SMEE. The opposite tendency was found for the participants who did not show the SMEE. SMEE observed

characters.

n.s.

: p<.001

Likeability rating

***

Likeability rating

Likeability rating

Fig 1. The visual patterns used in the experiments. Left: line drawings. Right: Bengal

***

SMEE NOT observed

n.s.

n.s.

Likeability rating

20 exposures ×4

Early phase of session

Subliminal mere exposure

2AFC

Fig 2. Schematic description of the experiment. After the presentation, the subjects judged their preference by likeability rating and 2AFC (two-alternative forced choice) task.

RESULT 1: Preference judgment Preference to the subliminally presented patterns (SMEE) was observed for 2/3 of the participants. No mere exposure effect was observed in the supraliminal condition. ***

OLD NEW

***

preference OLD

Fig 5. The result of likeability rating (top). The correlation between pupil size and likeability rating at the early phase of session (middle) and at the late phase of sesion (below).

: p<.001

Fig 3. The result of 2AFC task. In the task, participants were asked to select between two patterns, one that was previously presented (OLD) and another that was not presented before (NEW). Similar results were obtained in the likeability rating task.

Subliminal

r = .23, p < .05

Late phase of session

r = −.23, p < .01

CONCLUSION:

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Pupil response correlates with the induction of subliminal mere exposure. The preference to subthreshold visual patterns is gradually formed.

Supraliminal

Kahneman, D., & Beaty, J. (1966). Pupil Diameter and Load on Memory. Science, 23, 1583-1585.