How non-human animals recognize infants?
Caring infants is important but takes lots of cost. In many species not only mother but also other group members take care of infants and behave tolerantly toward them. What makes it possible?
I've studying cognitive mechanism underlying infant care in primates (i.e. capuchin monkeys, chimpanzees, bonobos) by comparative cognitive approach. For example, I adopted touch-panel task, eye-tracking, thermo-imaging etc. Infants of each species have specific features of their appearance. Interestingly, some of them are seen in many species while other are seen only certain species. For example, certain morphological features such as relatively bigger eyes and forehead, small nose and mouth, are observed in many species and called baby schema. On the other hand, in some species, infants have different coat or skin color from adults and the coloration differs among the species.
I am especially interested in how non-human primates recognize these features.
I've studying cognitive mechanism underlying infant care in primates (i.e. capuchin monkeys, chimpanzees, bonobos) by comparative cognitive approach. For example, I adopted touch-panel task, eye-tracking, thermo-imaging etc. Infants of each species have specific features of their appearance. Interestingly, some of them are seen in many species while other are seen only certain species. For example, certain morphological features such as relatively bigger eyes and forehead, small nose and mouth, are observed in many species and called baby schema. On the other hand, in some species, infants have different coat or skin color from adults and the coloration differs among the species.
I am especially interested in how non-human primates recognize these features.
Key Words
•Comparative cognition
•Primates
•Infant care
•Face recognition
•Infantile color
•Comparative cognition
•Primates
•Infant care
•Face recognition
•Infantile color
Capuchin monkeys can differentiate adult and infant of conspecifics and humans
Our study investigated whether capuchin monkeys can discriminate adult and infant from faces by using matching-to-sample task. We found that they can discriminate age category of both conspecifics and humans, but the learned age category did not generalized other species without additional training. This results indicate that capuchin monkeys are sensitive facial features signaling age category and they attend species-specific features.
Kawaguchi, Y, Kuroshima, H, & Fujita, K (2019). Age categorization of conspecific and heterospecific faces in capuchin monkeys (Sapajus apella). Journal of Comparative Psychology. |
Chimpanzees, but not bonobos prefer to look infants of conspecifics
Previous human studies found that we prefer to look infants. Interestingly, humans prefer infants of other species as well. We investigated whether chimpanzees and bonobos have such visual preference by using non-invasive eye-tracking. We presented the images of mother-and infants of chimpnazees, bonobos, Japanese macaques and tested how apes looked adult and infant faces. Results indicated that chimpanzees prefer to look conspecific infants than adults, but this preference was limited to own species. On the other hand, bonobos did not show any infant preference. Chimpanzee but not bonobo infants have special coloration on their faces. Our additional experiment found that this infantile colouration plays an important role for infant preference in chimpanzees. Chimpanzees and bonobos have interesting difference in their sociality. For example, infanticide is reported only in chimpanzees. Such infanticidal risk may have something to do with visual attention to infants. In addition, our study revealed that human's preference for infants of other species may be evolved relatively recently.
Kawaguchi Y, Kano F, Tomonaga M (2019). Chimpanzees, but not bonobos, attend more to infant than adult conspecifics. Animal Behaviour, Volume 154, Pages 171-181 |
Face color plays an more important role for age categorization than face shape
Chimpanzee faces change both in color and shape in accordance with their development. We investigated which feature they use to differentiate adult and infant faces. Chimpanzees were trained to differentiate adult faces and infant faces with a touch panel task. Then, we tested how their age category judgments transferred to a series of morphed faces which systematically differed in facial shape and color. Image analysis revealed significant differences both in shape and colour between adult and infant faces. However, we found that chimpanzees relay more on coloration for age categorization than facial shape. Our results showed that chimpanzees use unique infantile facial coloration as a salient cue when discriminating between adult and infant faces. The display of their developmental stages through facial colour may help chimpanzees to induce appropriate behavior from other individuals.
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Kawaguchi, Y., Nakamura, K. & Tomonaga, M.(2020). Colour matters more than shape for chimpanzees’ recognition of developmental face changes. Scientific Reports, 10.