Abstract
Accurate temporal expectation about an event should reflect its hazard rate, i.e., the probability it will occur in the next possible moment, given that it hasn't yet. Indeed, the speed of perceptual processing of visual stimuli has been found to change as a function of the hazard rate of those stimuli when varied between blocks of trials in visual recognition paradigms (Vangkilde, Coull, & Bundesen, 2012). In this study we investigated the dynamic adaptation of temporal expectation over time. We used two alternating hazard rates over the course of a variable cue-stimulus foreperiod, and measured participant response times in a speeded visual discrimination task. During the foreperiod, a coloured fixation cross would alternate between two colours, each denoting either a high or a low constant probability that the target stimulus would appear in the next possible moment. Foreperiods were distributed using discrete time steps of 400 ms, each with a high or a low probability that the stimulus would appear on that time step. Consecutive time steps with the same hazard rate were grouped together into epochs such that the probability that the stimulus would appear during the next time step was dependent on whether that time step was located during a high or a low probability epoch. We found significantly faster responses to stimuli presented during high probability epochs than during low probability epochs. This indicates that participants were not only able to adjust their temporal expectation, but could do so fast and flexible enough to reflect the change in hazard rate.
Meeting abstract presented at VSS 2017