Pupil dilation signals recognition salience

Stimuli that are recognized from a prior encounter elicit larger pupil dilations than those that are not. This study tests an account of this recognition dilation response (RDR) that assumes newly encountered recognition signals, like new percepts, elicit attentional orienting responses. Because orienting is moderated by motivational significance and expectation, the RDR was tested for these properties; manipulating incentives for old versus new judgments, and isolating the effects of runs of old versus new decisions on the subsequent RDR, in two experiments. Whereas incentivizing new decisions largely eliminated the RDR, incentivizing old decisions amplified it. Moreover, the RDR was prominent following runs of new decisions, yet minimal following runs of old decisions. Thus, the pupil dilates more as recognition memory becomes more valuable and/or unexpected. This recognition-orienting response was functionally separate from an additional, late dilation linked to feedback expectancy. Thus, the pupil separately signals the salience of recognition evidence, and the expectation of post-decision feedback.

Automated summary

Stimuli recognized from prior encounters lead to larger pupil dilations compared to new stimuli, a response that is moderated by motivational significance and expectation. Incentivizing new judgments can eliminate the dilation response, while incentivizing old judgments amplifies it. The pupil dilation reflects the salience of recognition evidence and the expectation of post-decision feedback, indicating separate cognitive processes.