Abstract
Primates are some of the most playful animals in the natural world, yet the reason for this remains unclear. One hypothesis posits that primates are so playful because playful activity functions to help develop the sophisticated cognitive and behavioural abilities that they are also renowned for. If this hypothesis were true, then play might be expected to have coevolved with the neural substrates underlying these abilities in primates. Here, we tested this prediction by conducting phylogenetic comparative analyses to determine whether play has coevolved with the cortico-cerebellar system, a neural system known to be involved in complex cognition and the production of complex behaviour. We used phylogenetic generalised least squares analyses to compare the relative volume of the largest constituent parts of the primate cortico-cerebellar system (prefrontal cortex, non-prefrontal heteromodal cortical association areas, and posterior cerebellar hemispheres) to the mean percentage of time budget spent in play by a sample of primate species. Using a second categorical data set on play, we also used phylogenetic analysis of covariance to test for significant differences in the volume of the components of the cortico-cerebellar system among primate species exhibiting one of three different levels of adult-adult social play. Our results suggest that, in general, a positive association exists between the amount of play exhibited and the relative size of the main components of the cortico-cerebellar system in our sample of primate species. Although the explanatory power of this study is limited by the correlational nature of its analyses and by the quantity and quality of the data currently available, this finding nevertheless lends support to the hypothesis that play functions to aid the development of cognitive and behavioural abilities in primates.
Highlights
Positive associations between the mean percentage of time budget spent in play and the relative sizes of: prefrontal cortex grey matter (R2 = 0.743, P = 0.022, k = 0; Fig. 1a), non-prefrontal heteromodal cortical association area grey matter (R2 = 0.717, P = 0.023, k = 0; Fig. 1b), posterior cerebellum (R2 = 0.835, P = 0.012, k = 0; Fig. 1c), prefrontal cortex grey matter and posterior cerebellum (R2 = 0.886, P = 0.012, k = 0; Fig. 1d), and non-prefrontal heteromodal cortical association area grey matter and posterior cerebellum (R2 = 0.930, P = 0.012, k = 0; Fig. 1e)
No significant associations were found between these play data and the relative sizes of the control structures, i.e. the primary visual cortex (R2 = 0.035, P = 0.801, k = 0.754; Fig. 1f) and the medial anterior cerebellum (R2 = 0.003, P = 0.902, k = 1; Fig. 1g)
In the second set of analyses we found significant differences between the most playful and the least playful species in the relative sizes of prefrontal cortex grey matter and non-prefrontal heteromodal cortical association area grey matter (Table 1)
Summary
One hypothesis posits that the distinctive quantity and quality of primate play are the result of a functional link between play and another distinctive characteristic of primates—their sophisticated cognitive and behavioural abilities. These include the capacity for extractive foraging, tool use, behavioural innovation, and complex sociality (e.g. Reader et al 2011). It has been a long-standing idea that the repetitive ‘experimental’. Primates (2017) 58:485–491 activity characteristic of play (Burghardt 2005) may function to train and maintain such abilities. Byers and Walker (1995) have suggested that play may function to develop the motor skills necessary for the execution of complex behaviours, while Pellis and Pellis (2009) and Panksepp and Biven (2012) have argued that play can serve to develop socioemotional intelligence
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
