Expectation expands subjective duration for repeated stimuli by altering perception.

Repeated stimuli are generally perceived to be shorter in duration than novel stimuli. Matthews (2015), however, demonstrated that when repetition is predictable, expectations of repetition may expand subjective duration for repeated stimuli. Although this effect is hypothesised to be perceptual, this has yet to be empirically established. The present study, therefore, examined perceptual and decisional factors in the repetition effect by using psychophysical methods while varying probabilities of repetition, in addition to replicating Matthews' original paradigm. Using faces with neutral expressions, 60 participants completed 2 judgment tasks, indicating whether a comparison stimulus was longer or shorter in duration than a standard stimulus preceding it. Comparison stimuli were presented for the same duration as the 500-ms standard in the replication task and for 1 of 7 durations (from 200-1,250 ms) in the crucial extension task, allowing for examination of sensitivity and bias. No evidence of bias was observed, but modulating participants' expectations of repetition affected perception, such that discrimination was more difficult under high than low repetition conditions. Overall, participants were more likely to judge stimuli that met expectations as longer, regardless of whether the expectation was repetition or novelty. Implications for models of repetition, context effects, and time estimation are discussed. (PsycINFO Database Record (c) 2019 APA, all rights reserved).