The effect of spatial layout on motion transparency

MARTÍN A.; BARRAZA J.F.; COLOMBO E.M.

Arezzo, Italia

Congreso; European Conference on Visual Perception; 2007

Universidad de Florencia, Dpto. de Psicología

It remains unclear how the visual system uses speed cues to segment images. Verghese and Stone (1997 Vision Research 37 397 - 406) showed that speed discrimination increases for segmented stimuli, suggesting that each discrete entity provides independent estimates of speed, which are combined across space. We present here evidence that motion transparency is constrained by spatial layout in the same direction as that reported by Verghese and Stone. We performed an experiment in which subjects had to discriminate between two stimuli, one containing two speeds (transparent) and the other containing five speeds. We measured the minimum speed difference as a function of the four layouts of Verghese and Stone. Stimuli were random-dot patterns displayed on circular patches located 9° away from the fixation point. We found that the smallest threshold was obtained for the maximally separated patch configuration and the threshold increased as the patches were brought closer. Results suggest that the effect of parsing the image into entities on speed discrimination facilitates the segmentation of layers in motion transparency.