Archived Abstracts
A Coevolutionary Relationship Between Striatum Size and Social Play in Nonhuman Primates
Authors: Kerrie Lewis Graham
This article analyses the evolutionary relationship between the frequency of social play behaviour among primates and the size of the striatum - a part of the brain that functions in the experience and anticipation of pleasure, reward, cognition, social modulation, and the sequence-selection of motor patterns. These are all behaviors deeply connected with playfulness. The striatum is additionally interesting to play researchers because it is connected to other brain regions associated with social play. This article demonstrates that striatum size has increased over evolutionary time in conjunction with increases in social play frequency in primates. That this relationship is not found with solitary play behavior, suggests that different types of play may have different evolutionary paths. For some animals (including humans), experiencing fun is considered rewarding and is crucial to risk-taking behavior, including some patterns of play. This is due to dopamine uptake in the striatum and other parts of the brain. Risk-taking could be beneficial if it helps animals learn and improve new physical and social skills, especially if the player can utilize those skills during emergency situations. For example, misjudging a branch during playful chase presents a real danger, but learning physical maneuvers to still reach safety might eventually prove invaluable. As such, brain regions including the striatum have been identified as important structures for play behavior, and may even have evolved as a functional network to support social play behavior. This article is important because it supports existing laboratory research, but extends the findings into an evolutionary framework.
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