The spatial spread of attentional modulation of the motion aftereffect

The spatial spread of attentional modulation of selective adaptation was in vestigated in four experiments in which the duration of the movement aftere ffect (MAE) was measured with and without processing of intermittently chan ging digits at the fixation point. In the first experiment, the effects of diverting attention on MAE duration were found to reduce as the distance be tween the fixation digits and the inner edge of the surrounding adapt/test grating was increased. A second experiment suggested that eye movements wer e unlikely to underlie the attentional effects. In experiment 3, the attent ional effect stayed constant as the outer diameter of the adapt/test gratin gs was increased. In experiment 4 (as in experiment 1) the modulatory effec ts of attention were larger the closer the adapt/test gratings were to the locus of attention, when the area of the grating was held constant but its eccentricity varied. In experiments 1 and 4, an intermittently changing fix ation digit was found to reduce MAE durations more than an unchanging digit , even when subjects were not required to process it, suggesting that exoge nous as well as endogenous attentional processes modulate early motion proc essing.