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Hsin-I Liao, Shinsuke Shimojo, Makio Kashino; Pupil constriction during visual preference decision. Journal of Vision 2014;14(10):1285. doi: 10.1167/14.10.1285.
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© ARVO (1962-2015); The Authors (2016-present)
Eyes reveal our internal cognitive status. In our previous studies, we found that gaze is biased towards the preferred image ("the gaze cascade effect", Shimojo et al., 2003), and this gaze bias has stronger accumulation for a familiarity preference than novelty preference (Liao & Shimojo, 2012). It also has been known that pupil dilates when we see someone attractive. Taken together, we aim to examine whether pupil dilation can be also a physiological marker for preference decision, and whether it reflects familiarity and novelty preference differently. A pair of a repeatedly presented image and a novel image was presented side-by-side on the screen. Three categories of images (faces, natural scenes, and geometric figures) were used and the paired images were always in the same category. Participants performed a two-alternative-force-choice (2AFC) preference task while their pupillary response was recorded. The images were presented with unlimited time until participants made their decision by pressing a button. Results showed that, to our surprise, instead of dilation, pupil constricts during the preference decision. Similar amounts of pupil constriction were observed for familiarity preference and novel preference. The effect of preference decision on pupil constriction was consistently observed in all the three stimulus categories we tested. Lower-level artifacts, such as average luminance changes or environmental lightings, are unlikely according to our stimulus parameters and pilot observations. The counterintuitive result that it is pupil constriction rather than dilation observed, is contradictive to predictions related to attractiveness or attention. Further studies are required to understand how mental states involving preference decision correspond to pupil response and its underlying mechanisms.
Meeting abstract presented at VSS 2014
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