Sensory processes.

Learning and Color Discrimination in the American Black Bear

“…For example, Walls (1942) in his compendium on the eye mentions research on color vision, much of which yielded questionable o r conflicting results, for only ten non-primates. The primates a r e the only mammals in which both behavioral and physiological data convincingly establish widespread hue perception (Grether 1940;Walls 1942;Diicker 1965;Rosengren 1969;Hess 1973). However, behavioral research since 1950 indicates that several non-primates, including swine (Klopfer 1966) and horses, squirrels and prairie dogs (see review in Hess 1973)) can readily discriminate between hues.…”

Sensory capacities of the chimpanzee: A review.

“…Using nine tones ranging from 14,400 to 37,500 cps the upper limit, defined as that value of the stimulus to which responses were made 50% of the time, for chimpanzees was 26,000 to 33,000 cps and for children was 22,600 to 23,700 cps. These values have been quoted by Maier and Schneirla (1935), Yerkes (1943), andHess (1960). On the basis of this apparently greater sensitivity to high frequencies, Yerkes (1943) speculated that the chimpanzee's sound world must be richer than the human's because he can perceive more natural sounds such as those made by insects.…”