Abstract
At VSS 2008, we presented a method using illusory motion (the Duncker illusion) to study the visual pathways serving cognition and action. Subjects' responses were influenced by illusory motion when asked to report the trajectory of a target using a cognitive-based task, but were not influenced by the illusion in a motor-based task. The purpose of the present study was to determine the magnitude of the illusory effects for cognitive-based tasks that are more comparable to the motor-based task.
Our previous cognitive-recall task could have been influenced by “relational momentum,” defined as an over-extrapolation of displacement when a target passes behind an occlusion. To address this, we had subjects perform an additional cognitive-recall task in which they were to select the location on the display where they last saw the target before the display concluded. This is different from our previous method because rather than extrapolating to the location toward which the target seemed to be heading, the subject directly chose the last remembered location.
In an additional cognitive-recall task, subjects were asked to estimate the target's trajectory. After conclusion of the display, subjects drew a line parallel to the remembered slope of the path of the target. Using this task, we examined how the subject perceived the trajectory of the target, rather than simply the remembered end position of the target.
All subjects reported illusory motion for both tasks; therefore we believe our experiments allow separate examination of the visual pathways utilizing comparable methods. Given these results, we have begun to look at how each of the pathways handle extraneous noise in a display.