Color Biases and Preferences in Zoo-Housed Chimpanzees (Pan troglodytes), Gorillas (Gorilla gorilla gorilla), and Japanese Macaques (Macaca fuscata).

Colors are an important signal for many primate species and have the potential to influence behavior and cognition. Primates may consciously or unconsciously prioritize their attention toward certain color stimuli to quickly identify consequential events, conspecifics, or resources. On the other hand, primates' color preferences can be modulated by memory, experiences, and affective responses. Few studies have explored the multifaceted nature of attention to colors in primate species that vary in their socioecologies and phenotypes, both of which may influence their responses to specific colors. The colors that rapidly capture primates' attention, and those they prefer, thus remain poorly understood. In a series of touchscreen experiments, we investigated responses to 9 perceptually distinct colored squares by 7 chimpanzees (Pan troglodytes), 11 gorillas (Gorilla gorilla gorilla), and 10 Japanese macaques (Macaca fuscata). We controlled for contextual cues known to influence color responses and assessed attentional biases using a dot probe task (Experiment 1) and preferences using a two-item forced-choice task (Experiments 2 and 3). In Experiment 1, we found that chimpanzees and gorillas showed the strongest attentional bias toward black, whereas the Japanese macaques showed the strongest bias toward red. These attentional biases suggest a potential relationship between species coloration and their attention to colors. In Experiments 2 and 3, all three species preferentially selected red, with Japanese macaques showing the strongest preference, supporting earlier findings that highlighted red as a particularly salient color to primates. Future research is needed to investigate the role of prior experience on primates' responses to colors.