Pupil dilation during recognition memory is influenced by cue-trace interactions but not by memory strength

Poster Session C - Sunday, April 14, 2024, 5:00 – 7:00 pm EDT, Sheraton Hall ABC

Wen Jian¹, Elena K. Festa¹, Mingjian He², William C. Heindel¹; ¹Brown University, ²Massachusetts Institute of Technology

During recognition memory tests, previously studied items elicit greater pupil dilation than unstudied items, a phenomenon termed the pupillary old/new effect. One popular explanation for this effect is that the magnitude of pupil dilation tracks the strength of the memory trace. However, recent findings suggest that it may reflect instead the interaction between the retrieval cue and the stored trace, as pupils dilate more in response to greater perceptual cue-trace match (“pupillary match effect”). To further examine these mechanisms, we investigated the pupillary effect following two study conditions that increase memory strength relative to single presentation but have differential effects on encoding: Distributed learning (with sporadic repetitions) enhances contextual recollection while massed learning (with immediate repetitions) minimizes contextual recollection but supports familiarity. Behavioral results showed that distributed learning improved recognition accuracy and confidence (both indexing memory strength) to a greater extent than massed learning relative to single-trial learning. However, the pupillary old/new effect remained comparable across the three conditions, showing no effect of memory strength. Moreover, distributed learning resulted in a larger pupillary match effect compared to single learning, while massed learning showed a reversed early pupillary match effect. Our results suggest that during recognition memory, the magnitude of pupil dilation reflects the nature of encoded trace and its interaction with retrieval cue, rather than memory strength per se. The increased pupillary match effect for distributed learning may reflect enhanced contextual recollection, while the reversed match effect for massed learning may reflect reduced retrieval effort associated with increased processing fluency.

Topic Area: LONG-TERM MEMORY: Episodic