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Exp Brain Res (2010) 203:671679 DOI 10.1007/s00221-010-2275-6
RESEARCH ARTICLE
The eVect of the Mller-Lyer illusion on saccades is modulated by spatial predictability and saccadic latency
Denise D. J. de Grave Nicola Bruno
Received: 15 August 2009 / Accepted: 20 April 2010 / Published online: 9 May 2010 The Author(s) 2010. This article is published with open access at Springerlink.com
Abstract Studies investigating the eVect of visual illusions on saccadic eye movements have provided a wide variety of results. In this study, we test three factors that might explain this variability: the spatial predictability of the stimulus, the duration of the stimulus and the latency of the saccades. Participants made a saccade from one end of a Mller-Lyer Wgure to the other end. By changing the spatial predictability of the stimulus, we Wnd that the illusion has a clear eVect on saccades (16%) when the stimulus is at a highly predictable location. Even stronger eVects of the illusion are found when the stimulus location becomes more unpredictable (1923%). Conversely, manipulating the duration of the stimulus fails to reveal a clear diVerence in illusion eVect. Finally, by computing the illusion eVect for diVerent saccadic latencies, we Wnd a maximum illusion eVect (about 30%) for very short latencies, which decreases by 7% with every 100 ms latency increase. We conclude that spatial predictability of the stimulus and saccadic latency inXuences the eVect of the Mller-Lyer illusion on saccades.
Keywords Saccades Eye movements Illusion
Perception Action
Introduction
Current models of the primate visual system propose a division between two visual systems: vision-for-perception (implemented by the V1-IT cortico-cortical (ventral) stream) and vision-for-action (the V1-PPT (dorsal) stream). This proposal (Milner and Goodale 1995; see also Jacob and Jeannerod 2003; Trevarthen 1968; Ungerleider and Mishkin 1982) has received support from human and monkey studies using diverse methods, including neuropsychology, imaging and psychophysics. However, the degree of functional independence between the two systems remains controversial. According to the original proposal (Goodale and Milner 1992) both visual systems operate independently. Vision-for-perception encodes object properties relative to the environment, on a relatively slow time scale and with conscious control, whereas the vision-for-action system uses spatial representations relative to the body, on a faster time scale than the vision-for-perception system and without the need for conscious...