Pro-saccades and anti-saccades to onset and offset targets.

Pro- and anti-saccades made to either onset or offset targets were examined to determine which of (1) changes in luminance or (2) the appearance of new peripheral objects, is more important in the reflexive generation of pro-saccades. In two experiments, pro-saccades had faster reaction times than did anti-saccades, but the difference was much greater for onset targets than offset targets (both with white targets on black backgrounds and black targets on white backgrounds). These findings suggest that there is a continuum of "prepotentness" in the oculomotor system with new peripheral objects being especially effective in generating reflexive pro-saccades.