Confusion of hues with grays by hooded rats

A total of 16 female Long-Evans rats, divided evenly into four groups, were presented with a chromatic stimulus paired with a chromatically neutral stimulus. The chromatic stimuli used were: red, yellow, green, and blue; each group was rewarded for responding to a different hue. The problem was divided into two phases; in Phase I, the training phase, the hue was paired with either a black or a white stimulus. Phase II consisted of pairing the hue with a chromatically neutral stimulus of various intensities. The neutral stimuli used in Phase II appeared as shades of gray ranging between black and white. All animals confused a hue with some shade of gray. The intensity of the gray which was confused with a hue was called the point of subjective equality (PSE); no evidence of color discrimination ability was found. The controversy over color vision was discussed. It was concluded that if color is salient for the rat, it did not appear so under the conditions and apparatus used in this study.