(with Michael Tarr)
Representational momentum (Freyd, 1987) is a phenomenon in which moving objects are remembered as appearing slightly past their actual final position. Freyd hypothesizes that this memory distortion results from dynamic visual representations that reflect an internalization of the inertial properties of real-world object motion. Moreover, she rejects the possibility that this distortion is the result of sensory mechanisms used for perceiving motion. In contrast, by introducing a temporal persistence constraint into the compution of low-level motion, the distortions associated with representational momentum may be explained by sensory mechanisms within early vision. This constraint simply assumes constant velocity for local surface patches over time. The model employing this constraint entails a highly parallel algorithm for computing velocity fields using information available directly in the intensity array, without requiring higher-level representations of visual information. Simulations were run using stimulus sequences that were similar to those used in the original psychophysical studies and were presented to an implementation of the model running on a Connection Machine. Conditions corresponding to coherent motion (under a variety of stimulus manipulations) yielded results in agreement with Freyd's psychophysical data -- exhibiting systematic distortions in the final positions of the objects. Conditions without coherent motion were also in agreement with human data -- lacking any systematic distortions. Thus, using a computational model of motion estimation that assumes temporal persistence we are able to account for the perceptual effects of representational momentum using only sensory mechanisms.
Black, M. J., Robust Incremental Optical Flow, Ph.D. Thesis, Yale University, Department of Computer Science, Research Report YALEU-DCS-RR-923, 1992. (abstract)
Tarr, M. J. and Black, M. J., Psychophysical implications of temporal persistence in early vision: A computational account of representational momentum, Investigative Ophthalmology and Visual Science Supplement, Vol. 33, May 1992, p. 1050.