Abstract
Whenever things change, accurate timing of events becomes crucial. This is the case when we have to localize a brief flash that is presented near the time of a saccade. To localize the flash, retinal information about its position must be combined with extra-retinal information about the changing eye position. Any temporal mismatch between the two kinds of information will result in the stimulus being seen at the wrong place. If temporal errors are (partly) responsible for the reported mislocalization of flashes presented just before, during or just after saccades, we should be able to manipulate the pattern of mislocalization by altering the perceived time of the flash. We therefore presented a rapid sequence of five bars (one red and four black; 10 ms intervals) at different positions around the time of a saccade. The task was to localize the red bar that was always either the second or the fourth in the sequence. We hypothesised that the resolution of human temporal order judgments is too poor to accurately identify the red flash’s position in the sequence, so subjects’ judgements of its timing will be shifted towards the centre of the sequence. If so, the asymmetrically timed black bars will introduce a systematic temporal error: the red bar will be perceived further in the direction of the saccade when it is presented early in the sequence than when it is presented late in the sequence. The results confirmed our hypothesis, showing a different mislocalization pattern for the two positions of the red bar within the sequence. Flash positions were misjudged in accordance with the flashes having been presented closer in time to the centre of the sequence. We conclude that temporal information is crucial for judging the spatial location of stimuli that are presented briefly near the time of saccades.
Meeting abstract presented at VSS 2013