The effects of illusory line motion on incongruent saccades: implications for saccadic eye movements and visual attention.

A complex neural problem must be solved before a voluntary eye movement is triggered away from a stimulus (antisaccade). The location code activated by a stimulus must be internally translated into an appropriate signal to direct the eyes into the opposite visual field, while the reflexive tendency to look directly at the stimulus must be suppressed. No doubt these extra processes contribute to the ubiquitous slowing of antisaccades. However, there is no consensus on the cognitive mechanisms that contribute to the antisaccade programme. Visual attention is closely associated with the generation of saccadic eye movements and it has been shown that attention will track an illusion of line motion. A series of experiments combined this illusion with a saccadic eye movement that was congruent (i.e. directed towards), or incongruent with (i.e. direct away from), a peripheral target. Experiment 1 showed that congruent saccades had faster reaction times than incongruent saccades. In contrast, Experiments 2 and 3 demonstrated that, with illusory line motion, incongruent saccades now had faster reaction times than congruent saccades. These findings demonstrate that an illusory phenomenon can accelerate the processing of an incongruent relative to a congruent saccade.