Suppressing where but not what: the effect of saccades on dorsal- and ventral-stream visual processing.

Some cognitive processes are suppressed during saccadic eye movements, whereas others are not. In two experiments, we investigated the locus of this interference effect. In one experiment, subjects decided whether pictured items were objects or nonobjects while making saccades of different lengths. Saccade distance had no effect on response time, indicating that saccades do not interfere with object recognition. However, in a second experiment, in which subjects decided whether pictured items faced to the left or to the right, response time increased with saccade distance, indicating that processing was suppressed during the saccade. These results (along with others) suggest that dorsal-stream (where) processes are suppressed during saccades, whereas ventral-stream (what) processes are not. Because the dorsal stream is instrumental in generating saccades, we propose that cognitive saccadic suppression results from dual-task interference within this visual subsystem.