Abstract
As in static depth perception, there are many cues to the spatial relationships between moving objects and the observer that need to be integrated into a coherent percept. Motion-in-depth involves a change in the position of an object relative to the observer over time and, specifically, along the line of sight. Despite some similarities, motion-in-depth differs from static depth perception with respect to the sources of relevant informational cues (e.g. optic flow, change-in-size of an object's boundary, disparity change over time, texture scale-change, and moving cast shadows). We psychophysically investigated visual cue integration of two cues to motion-in-depth by testing 3 subjects on a relative velocity judgement task. We independently manipulated optic flow information and binocular disparity information about the velocity of approaching objects. We also varied the reliability of each cue by adding noise in some conditions to see how cue reliability would affect the degree to which the information from each cue is weighted in combination. We found, for all 3 subjects, that cue integration occurred. However, our results did not follow the predictions of the Modified Weak Fusion model. Our results will be discussed in terms of other possible models of cue integration.