Researchers explore how infants infer social dominance relationships
Researchers explore how infants infer social dominance relationships
February 22, 2016 by Christopher Packham
(Medical Xpress)—The adaptive advantage of dominance relationships is obvious: In competition for food, mates and other resources, humans and animals try to minimize the cost of fighting by predicting their chances of succeeding in a conflict. Many species specifically exploit this sensitivity; for example, there are birds and animals that express postures under threat that make them appear to be larger. Biologists and anthropologists broadly accept that evolution has favored sensitivity to dominance relationships, but how these ancient perceptual functions work is still a subject of research.
Existing studies have shown that 10- to 13-month-old human infants are able to represent the dominance relationships between two agents in terms of their physical size, an appraisal in which larger size = more dominant. However, younger infants fail to do so. Are they failing to represent dominance relationships in general? Or do they lack sensitivity to physical size as a dominance cue?
Researchers at the University of British Columbia in Vancouver, B.C. have addressed this question by exploring whether infants younger than 10 months showed sensitivity to another marker for social dominance: numerical group size. They have published their results in the Proceedings of the National Academy of Sciences.
Inferring social dominance from group size is a key adaptive function for many species including lions, primates, birds and humans. The researchers note that while patrolling the borders of their territory, groups of chimpanzees engage in noisy hoot-pant calling in order to advertise their numbers. Biologists have noted that both chimpanzees and lions will refrain from intergroup conflict when outnumbered by such chimpanzee groups.
Noting that previous studies of human children aged six to eight years have demonstrated sensitivity to group size as a cue for social dominance, the researchers designed a video study to test children younger than 10 months old for similar sensitivity. Infants were introduced to two groups of different sizes; they were then introduced to a single agent from each group. When both agents attempted to cross a platform simultaneously, they bumped into each other, and the only way they could progress is if one agent yielded to the other.
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