Abstract
By using random-dot stereograms (RDS's) whose perception was slowed by a carefully calibrated proportion of stereoscopic noise, we studied the influence of haptics on the time necessary to perceive disparity-defined forms. Participants blindly felt a bas-relief version of a square or a circle. After a fixed amount of time the haptic surface was removed and vision was restored. A sparse RDS was then presented which contained a disparity-defined form that was either a square or a circle. The results revealed an intermodal interference effect. Response times were higher when the felt form was different from the disparity-defined form, relative to baselines times. However, this intermodal effect was virtually absent when the haptic surface was placed in a different egocentric location from that of the seen surface. The perceptual system efficiently combines haptic and visual information when perceiving 3D form. Our data suggest that this combination may involve low-level processes for solving the binocular correspondence problem, and that this process may be mediated by a common map of egocentric locations.