Social intelligence, innovation, and enhanced brain size in primates

Abstract

Despite considerable current interest in the evolution of intelligence, the intuitively appealing notion that brain volume and ''intelligence'' are linked remains untested. Here, we use ecologically relevant measures of cognitive ability, the reported incidence of behavioral innovation, social learning, and tool use, to show that brain size and cognitive capacity are indeed correlated. A comparative analysis of 533 instances of innovation, 445 observations of social learning, and 607 episodes of tool use established that social learning, innovation, and tool use frequencies are positively correlated with species' relative and absolute ''executive'' brain volumes, after controlling for phylogeny and research effort. Moreover, innovation and social learning frequencies covary across species, in conflict with the view that there is an evolutionary tradeoff between reliance on individual experience and social cues. These findings provide an empirical link between behavioral innovation, social learning capacities, and brain size in mammals. The ability to learn from others, invent new behaviors, and use tools may have played pivotal roles in primate brain evolution.

Explaining brain size variation: from social to cultural brain

“…However, it is entirely consistent with Reader and Laland's [32] proposal that general behavioral flexibility, not tied to any domain in particular (i.e. content-neutral), is the adaptation underlying cognitive performance in primates.…”

“…Across primate species, comparative studies have found that the performance of individual species on different cognitive tasks, involving aspects of spatial, physical and social cognition, is highly correlated [25,26,32,80], suggesting the presence of a general factor underlying this variation. They have also found that this general cognitive performance is correlated quite strongly with brain size, corrected slightly for the effects of body size [25,26].…”

“…These range from the ever-changing distribution of resources, which requires orientation and spatio-temporal memory abilities and some degree of planning of range use [27,28], to technical aspects of foraging, including tool use [19,29,30], to the presence of complex anti-predator strategies [31]. However, among primates these non-social cognitive abilities are mostly found in the same species that excel in the socio-cognitive ones [26,32], and thus do not explain much additional variation.…”

The evolution of social learning rules: Payoff-biased and frequency-dependent biased transmission

“…However, we do not interpret this as necessarily implying that there is an evolutionary tradeoff in social and asocial learning capabilities. To the contrary, the observed propensity for social learning and behavioural innovation (which is largely asocial learning) covaries strongly across non-human primates (Reader and Laland (2002)), and we expect this finding to apply generally. Rather, we interpret our findings as indicating regions of the parameter space in which reliance on social or asocial learning rules will differ in their utility.…”

Endocranial volumes of primate species: scaling analyses using a comprehensive and reliable data set

“…Various lines of evidence suggest that brain size in primates is both Primate endocranial volumes 3 correlated with cognitive abilities (Reader and Laland, 2002;Deaner et al, 2007) and influenced by a variety of social, ecological, and physiological variables (Clutton-Brock and Harvey, 1980;Byrne and Whiten, 1988;Sawaguchi, 1990;Aiello and Wheeler, 1995;Martin, 1996). The scaling relationship between brain size and body mass in primates (and mammals generally) has also been a major topic of debate, in part because the influence of body mass must be considered in comparative analyses of brain evolution (e.g.…”