Conscious perception seems to be a continuous stream of percepts. Is this true? Recent research sheds new light on this age-old debate.In long-lasting postdictive effects, later events can determine the perception of events that occurred several hundreds of milliseconds earlier.Long-lasting postdiction requires high capacity buffers, which store information unconsciously for substantial periods of time. This favors a two-stage model, in which continuous unconscious processing precedes discrete conscious percepts.Such a two-stage model solves the problems of both traditional continuous and discrete models.

Sensory information must be integrated over time to perceive, for example, motion and melodies. Here, to study temporal integration, we used the sequential metacontrast paradigm in which two expanding streams of lines are presented. When a line in one stream is offset observers perceive all other lines to be offset too, even though they are straight. When more lines are offset the offsets integrate mandatorily, i.e., observers cannot report the individual offsets. We show that mandatory integration lasts for up to 450 ms, depending on the observer. Importantly, integration occurs only when offsets are presented within a discrete window of time. Even stimuli that are in close spatio-temporal proximity do not integrate if they are in different windows. A window of integration starts with stimulus onset and integration in the next window has similar characteristics. We present a two-stage computational model based on discrete time windows that captures these effects.

Humans make two to four rapid eye movements (saccades) per second, which, surprisingly, does not lead to abrupt changes in vision. To the contrary, we perceive a stable world. Hence, an important question is how information is integrated across saccades. To investigate this question, we used the sequential metacontrast paradigm (SQM), where two expanding streams of lines are presented. When one line is spatially offset, the other lines are perceived as being offset, too. When more lines are offset, all offsets integrate mandatorily; that is, observers cannot report the individual offsets but perceive one integrated offset. Here, we asked observers to make a saccade during the SQM. Even though the saccades caused a highly disrupted motion trajectory on the retina, offsets presented before and after the saccade integrated mandatorily. When observers made no saccade and the streams were displaced on the screen so that a similarly disrupted retinal image occurred as in the previous condition, no integration occurred. We suggest that trans-saccadic integration and perception are determined by object identity in spatiotopic coordinates and not by the retinal image.

No abstract

No abstract

No abstract

Integration across space and time is essential for the analysis of motion, low contrast, and many more stimuli. A crucial question is what determines the duration of integration. Based on classical models of decision-making, one might expect that integration terminates as soon as sufficient evidence about a stimulus is accumulated and a threshold is crossed. However, there is very little research on this question as most experimental paradigms cannot monitor processing following stimulus presentation. In particular, it is difficult to determine when processing terminates. Here, using the sequential metacontrast paradigm (SQM), in which information is mandatorily integrated along motion trajectories, we show that the processing load determines the extent of integration but that evidence accumulation does not. Further, the extent of integration is determined by absolute time instead of the number of elements presented. These results have important implications for understanding the time course and mechanisms of temporal integration.