Pupillary Responses Reflect Image Memorability

Abstract

This study examined whether pupil size varies as a function of the memorability of natural scene images. In Experiment 1, participants were asked to memorize, recognize, and passively view high- and low-memorability images from an established dataset. The baseline-corrected pupil sizes were larger for high-memorability images, but only during old trials in the recognition phase. However, after implementing stricter controls for image luminance and arousal, pupil dilation for high-memorability images was observed across all phases: memorization, recognition, and passive viewing (Experiments 2 and 3). The effect of image memorability was further validated through item-based analysis. Both the pupil old/new effect and the subsequent memory effect were replicated, and these effects are probably separable from the effect of image memorability. The results of this study suggest that pupil size is sensitive to image memorability regardless of the behavioral task, supporting the view that image memorability is an intrinsic, higher-order property of the image.

Keywords: natural images; pupil old/new effect; pupillometry; recognition memory; scene perception; subsequent memory effect.