Cite as:
Fendrich R, Rieger J W, Heinze H-J, 2004, "The contribution of eye movements to anorthoscopic percepts under free-viewing conditions" Perception 33 ECVP Abstract Supplement

The contribution of eye movements to anorthoscopic percepts under free-viewing conditions

R Fendrich, J W Rieger, H-J Heinze

Our purpose was to investigate the contribution of pursuit eye movements to the integration of figures moving behind a slit (anorthoscopic perception). Outline shapes were moved across a simulated slit (without visible borders) on a CRT screen. Eye movements were monitored with a dual-Purkinje image eye-tracker. The slit width was adjusted so that there were spontaneous transitions between periods in which observers saw a horizontally moving shape and periods in which they saw only vertically moving contour segments. Subjects reported transitions between these alternative percepts. On half the trials the slit was retinally stabilised to eliminate pursuit-dependent retinal painting. During periods of figure perception, there was often low-amplitude spontaneous pursuit of the horizontal figure motion. Lower-amplitude pursuit was also sometimes observed when no figure was reported. Irrespective of figure perception, pursuit amplitudes were larger with stabilisation. However, the total percentage of time that a shape was seen, and the duration and frequency of episodes of figure perception, were not significantly different during stabilised and non-stabilised viewing. Our findings suggest that, although anorthoscopic figure percepts can elicit spontaneous pursuit under free-viewing conditions, this pursuit and the pattern it produces do not contribute to the formation or maintenance of those percepts.

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