the initial discriminations decreased the perceived similarity of parts (size or slant). This decrease resembles perceptual contrast. A discrimination between two parts also seems to increase the extent to which each part is apprehended as a separate group. Therefore, the conclusion accords with the position that two groups are associated with contrast, including for visibility.

The Weber fraction type of discrimination outcome means that stimuli of high magnitude are difficult to discriminate. Simultaneous and successive discriminations between two long (high magnitude) lines and also between two short (low magnitude) lines were carried out. Over-all performance on the successive discrimination between the two long lines was much poorer than on the three other discriminations. This discrimination also produced the poorest performance on different stimuli relative to same stimuli. The latter result should indicate that the two successive long lines were perceived as most similar. These and additional results support the conclusion that over-all discrimination performance and perceived similarity were consistently associated even though they were not consistently associated with length and time of occurrence (simultaneous versus successive). Nevertheless, the association of discrimination with perceived similarity has received minimal attention in the psychophysics area.

No abstract