Stimulus expectation prolongs rather than shortens perceived duration: Evidence from self-generated expectations.

Previous studies have suggested that unexpected stimuli are perceived as being longer than expected ones (e.g., the temporal oddball effect). These studies manipulated stimulus expectation mostly via stimulus repetitions and stimulus probabilities. However, these manipulations might affect duration judgments not only through the modulation of stimulus expectation. Therefore, the present study introduces a novel paradigm to isolate the effect of stimulus expectation on perceived duration from repetition and probability effects. In 2 experiments, participants vocalized which of 2 possible stimuli they expected in each trial immediately before stimulus presentation (self-generated expectations). Following stimulus presentation, participants performed a temporal bisection task on the duration of the presented stimuli. For both color (Experiment 1) and shape stimuli (Experiment 2), longer perceived durations were observed when stimulus expectations were fulfilled rather than violated. These results contrast with previous studies from which it has been concluded that stimulus expectation shortens perceived duration. Instead, the findings are rather in line with the idea that higher level stimulus expectation enhances stimulus processing and thus prolongs subjective duration (Matthews & Gheorghiu, 2016). Importantly, this also challenges the assumption that higher level stimulus expectation is a key mechanism driving the temporal oddball effect. (PsycINFO Database Record (c) 2018 APA, all rights reserved).