Pupil old/new effects reflect stimulus encoding and decoding in short‐term memory

Abstract

We conducted five pupil old/new experiments to examine whether pupil old/new effects can be linked to familiarity and/or recollection processes of recognition memory. In Experiments 1-3, we elicited robust pupil old/new effects for legal words and pseudowords (Experiment 1), positive and negative words (Experiment 2), and low-frequency and high-frequency words (Experiment 3). Importantly, unlike for old/new effects in ERPs, we failed to find any effects of long-term memory representations on pupil old/new effects. In Experiment 4, using the words and pseudowords from Experiment 1, participants made lexical decisions instead of old/new decisions. Pupil old/new effects were restricted to legal words. Additionally requiring participants to make speeded responses (Experiment 5) led to a complete absence of old/new effects. Taken together, these data suggest that pupil old/new effects do not map onto familiarity and recollection processes of recognition memory. They rather seem to reflect strength of memory traces in short-term memory, with little influence of long-term memory representations. Crucially, weakening the memory trace through manipulations in the experimental task significantly reduces pupil/old new effects.

Pupil dilation indicates the coding of past prediction errors: Evidence for attentional learning theory

“…In the current experiments, we examined how the pupil response elicited by cues during learning was linked to changes in error‐driven attention predicted by the Pearce‐Hall theory. Across a wide range of experimental paradigms, pupil size has been previously reported to be linked not only to learning (Eldar, Cohen, & Niv, ; Kahneman & Peavler, ; Lee & Margolis, ; Nassar et al, ; Reinhard & Lachnit, ; Reinhard, Lachnit, & Koenig, ) and memory (Brocher & Graf, ; Naber, Fraessle, Ruitshäuser, & Einhäuser, ; van Rijn, Dalenberg, Borst, & Sprenger, ), but also to attentional orienting (Corneil & Munoz, ; Geva, Zivan, Warsha, & Olchik, ; Lynn, ; Sokolov, ; Wang & Munoz, ) and the processing of uncertainty and error (Jepma & Nieuwenhuis, ; Nassar et al, ; O'Reilly et al, ; Preuschoff, t' Hart, & Einhäuser, ; Richer & Beatty, ; Satterthwaite et al, ). In extension of these previous findings, the current article examines how changes in pupil size during learning correspond to changes in error and error‐driven attention.…”

Response: Commentary: Pupil old/new effects reflect stimulus encoding and decoding in short-term memory

“…However, an alternative and, arguably, more parsimonious explanation is available. This explanation was tested in Brocher and Graf (2016), and the data of our Experiments 4 and 5 together with specific shortcomings of remember/know procedures do “challenge the view that pupil old/new effects can be directly mapped onto familiarity and/or recollection processes” (p. 1829).…”

“…In sum, while we truly appreciate the comments in Kafkas and Montaldi (2017), since they caution us to be very precise in our wording and underlying assumptions, they have little bearing on the actual data that we presented in Brocher and Graf (2016). We believe that, in bringing the two lines of research together, we first need to standardize the implemented materials and statistical analyses.…”

“…In Brocher and Graf (2016), we argued that using a remember/know procedure is not ideal to unambiguously establish that pupil size distinguishes familiarity and recollection because it is difficult to estimate what exactly drives larger pupils in “remember” than “familiar” responses. It is possible that the observed differences obtain because participants engage in different processes after they made a response.…”

“…In Brocher and Graf (2016), we conducted five pupil old/new experiments with materials that differently affect familiarity and recollection processes in ERPs. In all experiments, we used a simple old/new judgment task.…”