PERCEPTION OF APPARENT MOTION BETWEEN DISSIMILAR GRATINGS - SPATIOTEMPORAL PROPERTIES

What determines the strength of texture-defined apparent motion percep tion when the stimulus has no net directional energy in the Fourier do main? In a previous paper [Werkhoven, Sperling and Chubb (1993) Vision Research, 33,463-485] we demonstrated the counterintuitive finding th at the correspondence in spatial frequency and in modulation amplitude between neighboring patches of texture in a spatiotemporal motion pat h are irrelevant to motion strength. Instead, we found strong support for what we call a single channel or one-dimensional motion computatio n: a simple nonlinear transformation of the image, followed by standar d motion analysis. Here, we further studied the dimensionality of the motion computation in a parameter space that includes texture orientat ion and stimulus display rate in addition to texture spatial frequency and modulation amplitude. We used ambiguous motion displays in which one motion path, consisting of patches of nonsimilar texture, competes with another motion path comprised entirely of similar texture patche s. The data show that motion between dissimilar patches of texture tha t ace orthogonally oriented, have a two octave difference in spatial f requency and differ 50% in modulation amplitude can easily dominate mo tion between similar patches of texture. A single channel accounts for more than 70% of texture-from-motion strength for the parameter space examined and this channel is invariant for stimulus display rates var ying over a four-fold range.