Variable processing shifts during perceptual acceleration: Evidence from temporal integration

The perception of a stimulus can be accelerated by another that precedes it. Research to date has focused on quantifying this acceleration, and localizing it in the chain of perceptual and cognitive processes that are involved. This is challenging, because these processes may interact unexpectedly, and because traditional (univariate) analyses of brain activity and behaviour may conflate processes with the representations they act on. By using multivariate pattern analysis of EEG data from a missing element task, designed to measure the visual temporal integration of two successive stimulus displays, we were able to track the representation associated with the integrated percept. We manipulated the delay between our displays, and observed commensurate acceleration of the resultant integrated representation. Furthermore, regardless of the delay, we found that although processing was already accelerated during the earliest processing stages at around 100ms after stimulus onset, intermediate stages, at around 200ms, were even more accelerated. In contrast, later processing stages, at around 400ms, again showed less acceleration. The results thus suggest that perceptual acceleration during temporal integration is nonlinear, and that some time that is gained at one moment in the process can be lost again at another.