Visual attention mechanisms show a center-surround organization.

The sudden onset of a cue triggers visual attention, which then enhances visual processing in the zone near the cue. This enhancement causes a motion illusion in subsequent stimuli presented near the cue. At greater separations from the cue, the illusory motion reverses direction, indicating prolonged processing speed. Measurements of the strength and direction of illusory motion at increasing separations from the cue reveal an attentional 'perceptive field' with an excitatory center at the locus cued and an inhibitory surround subtending the remaining visual field. These findings help explain the traditional attentional 'benefits' and 'costs' of attention.