Two experiments were carried out in order to clarify the color perception in sheep. In Exp.I, one Suffolk ewe was trained, using a T maze in which she went behind the color card in order to obtain feed, to discriminate between simultaneously presented colored and gray cards. Three colors, red, green and blue, were used as the positive stimuli. Negative stimuli using discrimination from these colors were seven gray cards including the same luminosity as each color. In Exp.II, twin Corridale lambs were trained using an operant conditioning technique to press a switch under the positive stimulus color card to receive feed as a reward. It was tested whether or not the lambs could discriminate between three colors (red, green and blue) and gray with the same luminosity as each color, and between red and green, as well as yellow and blue with the same luminosity. In both experiments, the sheep succeeded in all discrimination tests except for one case in which the one of twins could not distinguish between green and gray.
