Object Tracking via Spatiotemporal Continuity Vs. Surface Features
The individuation of objects via spatiotemporal continuity and surface features, such as texture and orientation, was studied with a streaming-bouncing paradigm. In a typical display, two moving discs start on opposite sides of the screen and move toward each other, coincide, and then reverse directions. If the discs share identical surface features, the perception of the event is ambiguous and the discs could be perceived as streaming or bouncing. If the discs are not identical, distinctive features could disambiguate this percept. The following experiments were designed to explore how surface features interact with spatial-temporal information and bias the percept toward streaming or bouncing. Four experiments were conducted in which participants judged whether the two discs (1.5[sup]0[/sup] visual angle) streamed or bounced (constant velocity = 3.5 horizontal deg/sec) as they moved across a grey background. Between-subject variables included trajectory (horizontal vs. diagonal) and surface features (luminance gratings or random dots). The orientations of the gratings for the two discs differed by 0, 15, 30, or 45 deg; the probability density distributions for the random dots differed by 0, 10, or 20%. In each experiment, there were three conditions mediating the intersection of the two discs (occlusion, transparency, or visible occluder), which were programmed to bounce on every trial. Participants were presented with a total of 288 trials with 24 (luminance grating) or 32 (random dots) per intersection condition by surface feature difference (ΔF). Consistent with previous studies, the results revealed a significant bias to perceive streaming (on average 80% with ΔF=0) in the transparent and occluder conditions, which decreased as a function of ΔF. By contrast, the likelihood of perceiving streaming in the occlusion condition rarely exceeded 30%. These results also interacted with trajectory and surface feature. Taken together, these results suggest that multiple processes are involved in individuating objects.
Vision Sciences Society Annual Meeting (VSS)
Harding, Samuel, Ty W. Boyer, Bennett I. Bertenthal.
"Object Tracking via Spatiotemporal Continuity Vs. Surface Features."
Psychology Faculty Presentations.