The Muller-Lyer illusion as a perturbation to the saccadic system

An eye targeting task was employed to investigate saccadic bias and endpoint variability as a function of target size and configuration, and movement amplitude. The Muller-Lyer (ML) illusion was used to create illusory target endpoints which biased the amplitude of saccadic movements in the direction predicted by the efferent theory of perception/misperception. Target amplitude affected saccadic bias and variability in a manner consistent with the range effect and the force-force variability relation. Target size had no impact on endpoint consistency. Amplitude and illusory effects appear to be independent and may reflect different levels of visual-motor processing. (C) 1999 Elsevier Science B.V. All rights reserved.