Competition for consciousness among visual events: The psychophysics of reentrant visual processes

Advances in neuroscience implicate reentrant signaling as the predominant form of communication between brain areas. This principle was used in a series of masking experiments hat defy explanation by feed-forward theories. The masking occurs when a brief display of target plus mask is continued with the mask alone. Two masking processes were found: an early process affected by physical factors such as adapting luminance and a later process affected by attentional factors uch as set size. This later process is called masking by object substitution, because it occurs whenever there is a mismatch between the reentrant visual representation a d the ongoing lower level activity. Iterative reentrant processing was formalized in a computational model that provides an excellent fit to the data. The model provides amore comprehensive account of all forms of visual masking than do the long-held feed-forward views based on inhibitory contour interactions. From the time a stimulus first enters the eye to the time a percept emerges into consciousness, the initial stimulus has been coded at several evels in the visual system. One of the main goals in studying visual information processing is to specify the represen-tations at each level and the temporal sequence between the