Visual pattern-discrimination in the vertebrates - III. Effective differences in width of visible striae for the monkey and the chick.

Abstract

Ascertained the difference in width of 2 regular systems of striae that was necessary to effect discrimination between the two systems by the animals. The discriminands were 2 interchangeable circular fields, 6 cms in diameter and equal in brightness and color. A young male Capuchin monkey and 2 Indian gamecocks were used. The bird's eyes were refracted by skiascopy. Results show that the monkey could distinguish difference in width of striae of less than 3%. Chick 2 ceased to discriminate when difference in width was reduced to between 33% and 42%. The discriminative ability shown by the monkey was 10 times as great as that shown by Chick 2. This disparity suggested that difference of width between 2 systems of visible striae constituted a more difficult basis of discrimination for the chicken than the mere presence of striae. (PsycINFO Database Record (c) 2006 APA, all rights reserved)