A superposition of moving and static stimuli appears to dilate in time when the moving stimulus is attended to

摘要

A moving stimulus appears to last longer than a static one. This time dilation in a moving stimulus has been explained by stimulus domains, such as temporal frequency and speed (e. g. Kanai et al., 2006; Kaneko & Murakami, 2009). However, previous studies have presented moving and static stimuli separately, and it is still unknown whether the observer's attentional set to the moving stimulus affects perceived duration when the moving and static stimuli overlap in the same location. We presented moving and static random-dot patterns simultaneously within the same field and instructed the observer to attend to either one of these patterns colored differently. We measured the perceived duration of the attended pattern in the two-interval forced-choice paradigm with the method of constant stimuli. The standard stimulus consisted of 300 moving dots and 300 static dots whereas the comparison stimulus consisted of 300 static dots. The standard stimulus appeared to last longer when the moving stimulus was attended to than when the static one was attended to, even though the physical display was the same between conditions. Subsidiary experiments demonstrated that the difference in perceived duration between the attend-to-moving and attend-to-static conditions increased proportionally to the physical duration and that, compared to the apparent duration of a static pattern alone, attending to the static pattern in the superposition did not last shorter when it was added to the moving pattern that had already appeared for one second. These results indicate that endogenous attention to a moving stimulus is a crucial component of the time dilation and that a simultaneously appearing stimulus within the superposition can draw exogenous attention, affecting the perceived duration. In the pacemaker-accumulator framework, these effects can be explained by selective accumulation of temporal units by feature-based attention.