Summary
All the experiments show that perceptual organization is time dependent. Proximity grouping can be perceived much faster than similarity (shape or luminance) based grouping. Our experimental paradigm shows that shape similarity and luminance similarity are built up between 60 and 160 msec SOA while proximity is built up in less than 60 msec. While proximity grouping is a fast process, it can be taken over by similarity cues when they are later perceived. The system appears to be very sensitive to small variations in spacing ratios.