title: 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.
authors.affiliation: Department of German Literature and Linguistics I, University of Cologne, Cologne, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Brocher
authors.affiliation: Department of German Literature and Linguistics I, University of Cologne, Cologne, Germany.
authors.forename: Tim
authors.initials: T
authors.lastname: Graf
mesh_terms: D006801:Humans; D008570:Memory, Short-Term / Q000502:physiology*; D011939:Mental Recall / Q000502:physiology*; D011680:Pupil / Q000502:physiology*; D021641:Recognition, Psychology / Q000502:physiology*
keywords: Dual-process model; Old/new effects; Pupillometry; Recognition memory