Effects of amount of attention allocated to the location of visual stimulus pairs on perception of simultaneity

Abstract

This study examined whether a change in the amount of attention equally allocated to two locations affects judgments of the simultaneity or successiveness of stimuli presented at those locations. Observers were cued to expect two brief flashes either to the left and right of fixation or above and below fixation. Stimulus onset asynchrony was randomly varied. On a small proportion of trials, the stimuli appeared at the unexpected locations. Observers were more likely to report the stimuli as simultaneous when they appeared in the unexpected locations. A model proposed to account for the data assumes that a brief stimulus event is represented by a probability distribution reflecting the uncertainty in determining the time of the event's occurrence, and two events are judged to be simultaneous if they are perceived to fall within some critical temporal interval, c, which is a function of the amount of attention allocated to the task.