Abstract
Object recognition is a type of perception that enables observers to recognize familiar shapes and categorize them into real-world identities. In this preregistered study, we aimed to determine whether pupil size changes occur during the perception and recognition of identifiable objects. We compared pupil size changes for familiar objects, nonobjects, and random noise. Nonobjects and noise produced greater pupil dilation than familiar objects. Contrary to previous evidence showing greater pupil dilation to stimuli with more perceptual and affective content, these results indicate a greater pupil dilation to stimuli that are unidentifiable. This is consistent with the relative salience of novelty compared to familiarity at the physiological level driving the pupil response.
Highlights
Pupil size changes are reflexive; the pupil grows and shrinks unconsciously in response to varying levels of light (Ellis, 1981), but it changes in size depending on the content of the stimulus
We focus on the pupillary responses to object recognition, in order to deepen our understanding of the cognitive influences on the pupillary response as well as on object recognition itself
The field of pupillometry is currently evolving to determine how the magnitude of pupil dilation is affected by these various factors
Summary
Pupil size changes are reflexive; the pupil grows and shrinks unconsciously in response to varying levels of light (Ellis, 1981), but it changes in size depending on the content of the stimulus This cognitive influence on the pupillary response has been long established (Beatty & Lucero-Wagoner, 2000; Loewenfeld, 1958), but its precise nature is less clear (Mathot, 2018). Kafkas and Montaldi (2015) showed subjects a range of familiar objects during a training phase and measured the pupil responses to a set of test objects, some of which had been presented in the training phase They found that the test objects that had been seen during the training phase produced a greater pupil dilation than the ones not previously seen. Consistent with the results of Kafkas and Montaldi (2015), a greater pupil dilation was observed for the memorized scenes, while the novel scenes produced a pupil constriction that became larger as a function of confidence
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