Abstract
Introduction
We are interested in determining the level at which perceptual after-effects occur. Depth after-effects appear to be driven by adaptation at a surface representation level, rather than retinally-defined characteristics. For example, Domini, Adams & Banks (2001) showed that prolonged viewing of a stereoscopically defined curved surface produces after-effects related to the perceived curvature rather than the pattern of retinal disparities per se. Similarly, Köhler & Emery (1947) presented oppositely oriented lines alternately to two eyes but failed to find the depth after-effects predicted by low-level, monocular adaptation mechanisms.
We investigated whether:
Monocular adaptation to tilted Gabor patches leads to binocular slant after-effects (SAE), or
Binocular adaptation to a slanted surface produces monocular tilt after-effects (TAE).
Methods
After monocular or binocular adaptation, the amount of TAE and SAE were measured by the method of constant stimuli. The adaptation stimuli were Gabor patches rotated by ±3? from vertical presented to the left and right eyes. In the binocular condition they were presented to both eyes simultaneously, creating a percept of a slanted surface with zero tilt. The same stimuli were used for monocular adaptation, but were presented to the eyes alternately, creating percepts of zero-slant, tilted surfaces. Top-ups of the adaptation stimuli were presented between trials.
Results & Conclusions
Binocular adaptation produced large SAEs and smaller TAEs. Monocular adaptation produced large TAEs and smaller but clear SAEs, in contrast to Köhler & Emery's findings. This pattern of results suggests that a common, low-level adaptation to monocular orientation is involved in slant and tilt after-effects. However, the incomplete transfer between slant and tilt makes it clear that higher level adaptation is also involved, perhaps at the level of surface representation.
WJA funded by HFSP grant RG0109/1999-B