Color discrimination and color preferences in Chimpanzees (Pan troglodytes)

Chimpanzees (Pan troglodytes) have been known for a long time to have color vision identical to humans (Grether in J Comp Psychol 29(2):167-177, 1940b; Jacobs et al. in Vis Res 36(16):2587-2594, 1996). With this study, we wonder if chimpanzees, as humans, show preferences for some colors rather than others. During a first range of experiments, we test their ability to discriminate all the colors from our set, through easy matching-to-sample tasks. The seven chimpanzees that participate in this first test show the results we can expect from chimpanzees with normal color vision. Then, six of them are tested for preferences. This range of experiments results in the existence of consistent tendencies across all the trials and situations, as chimpanzees would mostly first choose some particular colors, and conversely choose last different colors. Although the results for color discrimination are identical for all the seven chimpanzees, preference tests demonstrate four different tendencies. This study is the first step toward broader experiments, including more chimpanzee subjects, but also different species, with the only requirement of being trained to the basic use of a touch panel interface.