Color discrimination by rhesus monkeys

Rhesus monkeys (Macaca mulatta) were trained to discriminate standard stimuli which were Munsell papers differing considerably in Hue, Value, and Chroma. They were then given stimuli lying between the standards and were required to match each stimulus to one of the standards. Matching depended on changes in one dimension, as well as simultaneous changes in two or more dimensions, e.g. a change in Hue and Value was more likely to lead to a shift in matching than a change in either alone. Other Es using unlike stimulus dimensions, e.g. form, size, and color, reported that cues must be equally potent to summate. In the present study, however, additivity occurred in spite of cue dominance.