Orientation mechanisms in stereoscopic vision: an individual differences approach

The stereoscopic system is typically tested by measuring its response to sinusoidal disparity corrugations. Previous research using psychophysical methods like masking and adaptation has provided evidence about the existence of disparity mechanisms tuned to spatial frequency and orientation. Analyses based on individual differences have confirmed only the existence of disparity mechanisms tuned to spatial frequency. The main objective of this study is to investigate the existence of orientation-selective disparity mechanisms using an individual differences approach. We measured the disparity thresholds of 37 subjects using sinusoidal disparity corrugations constructed from dynamic random-dot stereograms with spatial frequencies of 0.1, 0.4, and 0.8 cpd and 7 orientations (ranging from 0° to 90° in steps of 15°). Stereo thresholds for 0.1 cpd showed a strong anisotropy with disparity thresholds increasing from 90° (horizontal) to 0° (vertical). This anisotropy was reduced for the other two spatial frequencies. Component and factor analyses revealed that closer orientations tend to group together, suggesting the presence of underlying orientation-selective mechanisms in stereovision. These results provide new evidence for disparity channels tuned to orientation underlying the processing of disparity corrugations.