LOCAL AND GLOBAL FACTORS AFFECTING THE COHERENT MOTION OF GRATINGS PRESENTED IN MULTIPLE APERTURES

Using stimuli composed of two independent gratings viewed through mult iple apertures. we investigate a number of parameters affecting the in tegration of locally ambiguous motions into globally coherent motion. In four experiments, we varied local factors (grating spatial frequenc y, speed, contrast, duty cycle, orientation) and global factors (degre e of similarity and common fate between the gratings, and symmetry in the configuration of the grating pattern) and examined their effects o n global motion coherence. Our results, confirming accounts offered by previous investigators, indicate that local competition between motio n signals generated by contours (ambiguous) and their line termination s (unambiguous) is important in determining global motion coherence in multiple-aperture stimuli. Our results also indicate that global fact ors can affect perceived coherence independently of local motion signa ls, suggesting the involvement of higher-level motion areas and a role for non-motion processes such as those involved in pattern and form p erception. Comparing motion coherence with other two-dimensional (2-D) stimuli (plaids) shows that 2-D multiple-aperture stimuli are not ana logous and that coherence models derived from plaid stimuli do not acc ount for the data. (C) 1998 Elsevier Science Ltd. All rights reserved.