Decision-related factors in pupil old/new effects: Attention, response execution, and false memory

- Task-related focus of attention affects pupil old/new effects.
- Response execution does not affect pupil old/new effects.
- Pupil old/new effects contain a veridical and a subjective component of oldness.
- Pupil old/new effects are more strongly related to the intentional than the automatic use of memory.

In this study, we investigate the effects of decision-related factors on recognition memory in pupil old/new paradigms. In Experiment 1, we used an old/new paradigm with words and pseudowords and participants made lexical decisions during recognition rather than old/new decisions. Importantly, participants were instructed to focus on the nonword-likeness of presented items, not their word-likeness. We obtained no old/new effects. In Experiment 2, participants discriminated old from new words and old from new pseudowords during recognition, and they did so as quickly as possible. We found old/new effects for both words and pseudowords. In Experiment 3, we used materials and an old/new design known to elicit a large number of incorrect responses. For false alarms (“old” response for new word), we found larger pupils than for correctly classified new items, starting at the point at which response execution was allowed (2750 ms post stimulus onset). In contrast, pupil size for misses (“new” response for old word) was statistically indistinguishable from pupil size in correct rejections. Taken together, our data suggest that pupil old/new effects result more from the intentional use of memory than from its automatic use.