Abstract
Purpose. Prolonged viewing of a stereoscopic slanted plane causes a gaze-normal plane to appear slanted in the opposite direction. This after-effect can be explained by change in stereoscopic slant gain or by channel fatigue. To determine if the gain changes, we examined the effect of slant adaptation on slant discrimination thresholds. Stimuli. We presented stereoscopic planes textured with sparse random dots. The planes were slanted about a vertical or horizontal axis. To minimize perspective cues, the texture was “back-projected” and the clipping window was elliptical with a random major axis. Procedure. The initial adaptation stimulus was presented for 240 sec. Size and direction of the adaptation effect was measured by a slant-nulling task. Discrimination thresholds were obtained with a 2-IFC procedure and interleaved staircases. The adaptation stimulus was re-presented for 2 sec between trials. Results. Discrimination thresholds decreased by roughly a factor of two for base slants within 20 of the adapting stimulus. Thresholds increased for base slants greater than 20 and less than 40 from the adapting slant. Conclusion. Stereoscopic slant adaptation aid discrimination performance when the test stimulus has roughly the same slant as the adapting stimulus