Wen Jian¹ (), Elena K. Festa¹, William C. Heindel¹; ¹Brown University

Our pupils change size not only in response to light, but also to internal cognitive processes. Pupil dilation has been linked to activity within the locus coeruleus noradrenergic arousal system. During tests of recognition memory, greater pupil dilation is elicited by studied than new items, although the mechanism underlying this pupillary old/new effect remains elusive. Recent findings suggest that it may reflect the interaction between the retrieval cue and the stored memory trace, as pupils dilate more in response to greater perceptual cue-trace match. We aimed to investigate how this pupillary match effect is influenced by encoding intentionality and stimulus repetition. Two groups of healthy young adults completed either incidental or intentional encoding of visual stimuli presented under two repetition conditions: Distributed learning (which enhances contextual recollection) and massed learning (which minimizes contextual recollection but supports familiarity). A subsequent test phase consisted of previously studied items under varying cue-trace match plus novel items. As expected, recognition accuracy was greater following intentional than incidental encoding as well as distributed than massed learning. Following distributed learning, incidental and intentional encoding produced comparable pupillary old/new and cue-trace match effects. Following massed learning, incidental encoding produced an early reversed pupillary match effect along with a reduction in the normal match effect, whereas intentional encoding produced a reduction in the early reversed match effect along with a reemergence of the match effect observed under distributed learning. These results suggest that the magnitude of pupil dilation reflects the nature of encoded traces and its interaction with retrieval cues during recognition memory. The pupillary match effect following distributed learning may reflect enhanced contextual recollection, while the early reversed match effect following incidental, massed learning may reflect reduced retrieval effort associated with increased processing fluency, and this implicit processing effect may be reduced following intentional massed learning.