Discrimination learning decreases perceived similarity according to an objective measure.

UNLABELLED: Initial identification discriminations between two sizes and between two slants produced better overall performances on subsequent size and slant same-different discriminations, respectively. This size- and slant-specific transfer was due to an improvement on only the different pairs. Time-duration identification discriminations with the identical stimuli and response assignments improved neither overall same-different performances nor performances on different pairs. A good performance on different pairs relative to same pairs should indicate a low perceived similarity. The literature indicates that A-X and B-Y pairings produce a positive transfer on an A-versus-B discrimination when X and Y are relatively low in similarity, and also indicates that a low perceived (not physical) similarity improves discrimination learning. An increase in salience should have also improved performance on the same pairs. THE
CONCLUSION: 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.