Pupil dilation accompanying successful recognition is linearly related to memory precision.

In a recognition memory task, correct "old" responses to previously studied target items (hits) trigger larger pupil dilation (PD) than correct "new" responses to previously not presented foil items (correct rejections). This pupil old/new effect reflects the specific processes involved in recognition decisions, with dilation being larger when decisions are based on recollection of contextual details rather than mere familiarity. However, previous research has been limited in determining the exact link between PD and recognition processes due to the categorical nature of tasks used to assess recollection/familiarity. To investigate this issue, we examined whether the precision of the recollected memory representation is related to PD during successful recognition. During encoding, target words were presented on the outline of an invisible circle, and during a subsequent recognition task, participants made old/new decisions. For "old" responses, participants had to indicate the exact location of the target on the outline of the invisible circle. We found that larger PD during the old/new decision was related to more precise subsequent localization decision. Furthermore, we also demonstrated that PD and memory precision are linearly related, and even hits followed by unprecise source localization trigger larger PD than correct rejections. Thus, increased PD is present for all recognition decisions, but its magnitude increases with increasing precision of source recollection. This pattern of results suggests that the pupil old/new effect might originate from two distinct components: The first is related to the mere recognition of a word, whereas the second reflects the quality of recollected source information. (PsycInfo Database Record (c) 2025 APA, all rights reserved).