Perceptual association enhances intersensory temporal precision

The brain is able to extract associative regularities between stimuli and readjust the perceived timing of correlated sensory signals. In order to elucidate whether these two mechanisms interact with each other or not, we exposed participants to two different visual stimuli (a circle and a triangle) that appeared continuously and unpredictably, for 5min. While the circle always preceded the tone for 700ms, the triangle did not. Yet, the triangle could appear, by chance, before and after the tone, and between the circle and the tone. In two different test blocks, conducted before and after the 5-min exposure phase, participants performed simultaneity judgments regarding one of the visual stimuli (the circle or the triangle) and the exposed tone presented at different stimulus onset asynchronies. The results revealed that the precision at judging the temporal relation between the 'associated figure' (the circle) and the tone increased significantly after the 5-min exposure. This effect was not observed for the non-associated figure (the triangle) and occurred even when participants reported to be unaware of any association between the stimuli presented. This pattern of results indicates that the perceptual association between sensory signals can influence their subjective temporal processing.