title: Chimpanzees can visually perceive differences in the freshness of foods.
abstract: Colour vision in primates is believed to be an adaptation for finding ripe fruit and young leaves. The contribution of the luminance distribution, which influences how humans evaluate the freshness of food, has not been explored with respect to the detection of subtle distinctions in food quality in non-human primates. We examined how chimpanzees, which are closely related to humans, perceive the freshness of foods. The findings suggest that chimpanzees were able to choose fresher cabbage based on both colour and grey-scale images. Additional tests with images of novel cabbage, spinach, and strawberries revealed that one chimpanzee could detect the freshness of other fruits and vegetables. The critical factor in determining the judgements of freshness made by the chimpanzees was the spatial layout of luminance information. These findings provide the first known evidence that chimpanzees discriminate between images representing various degrees of freshness based solely on luminance information.
authors.affiliation: Department of Information Systems, Faculty of Information Culture, Niigata University of International and Information Studies, 3-1-1, Mizukino, Nishi-ku, Niigata, 950-2292, Japan.
authors.forename: Tomoko
authors.initials: T
authors.lastname: Imura
authors.affiliation: Faculty of Human Sciences, Bunkyo University, 3337, Minami-ogishima, Koshigaya, Saitama, 343-8511, Japan.
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Masuda
authors.affiliation: Laboratory of Sensory Science, Food Research Institute, National Agriculture and Food Research Organization, 2-1-12, Kannondai, Tsukuba, Ibaraki, 305-8642, Japan.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Wada
authors.affiliation: Language and Intelligence Section, Primate Research Institute, Kyoto University, 41-2 Kanrin, Inuyama, Aichi 484-8506, Japan.
authors.forename: Masaki
authors.initials: M
authors.lastname: Tomonaga
authors.affiliation: Faculty of Environment and Information Sciences, Yokohama National University, 79-7, Tokiwadai, Hodogaya-ku, Yokohama, Kanagawa, 240-8501, Japan.
authors.forename: Katsunori
authors.initials: K
authors.lastname: Okajima
mesh_terms: D000818:Animals; D003116:Color; D005260:Female; D063427:Food Quality; D005638:Fruit; D007600:Judgment; D008297:Male; D002679:Pan troglodytes / Q000502:physiology*; D010775:Photic Stimulation; D014796:Visual Perception / Q000502:physiology*