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.

Social learning (learning through observation or interaction with other individuals) is widespread in nature and is central to the remarkable success of humanity, yet it remains unclear why it pays to copy, and how best to do so. To address these questions we organised a computer tournament in which entrants submitted strategies specifying how to use social learning and its asocial alternative (e.g. trial-and-error) to acquire adaptive behavior in a complex environment. Most current theory predicts the emergence of mixed strategies that rely on some combination of the two types of learning. In the tournament, however, strategies that relied heavily on social learning were found to be remarkably successful, even when asocial information was no more costly than social information. Social learning proved advantageous because individuals frequently demonstrated the highest-payoff behavior in their repertoire, inadvertently filtering information for copiers. The winning strategy (discountmachine) relied exclusively on social learning, and weighted information according to the time since acquisition.Human culture is widely thought to underlie the extraordinary demographic success of our species, manifest in virtually every terrestrial habitat (1-2). Cultural processes facilitate the spread of adaptive knowledge, accumulated over generations, allowing individuals to acquire vital life skills. One of the foundations of culture is social learning -learning influenced by observation or interaction with other individuals (3) -which occurs widely, in various forms, * To whom correspondence should be addressed. ler4@st-andrews.ac.uk.One sentence summary: A computer tournament helps to explain why social learning is common in nature and why human beings happen to be so good at it. NIH Public Access Author ManuscriptScience. Author manuscript; available in PMC 2010 November 22. Published in final edited form as:Science. 2010 April 9; 328(5975): 208-213. doi:10.1126/science.1184719. NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript across the animal kingdom (4). Yet it remains something of a mystery why it pays individuals to copy others, and how best to do this.At first sight, social learning appears advantageous because it allows individuals to avoid the costs, in terms of effort and risk, of trial-and-error learning. However, social learning can also cost time and effort, and theoretical work reveals that it can be error prone, leading individuals to acquire inappropriate or outdated information in nonuniform and changing environments (5-11). Current theory suggests that to avoid these errors individuals should be selective in when and how they use social learning, so as to balance its advantages against the risks inherent in its indiscriminate use (9). Accordingly, natural selection is expected to have favoured social learning strategies, psychological mechanisms that specify when individuals copy, and from whom they learn (12-13).These issues lie at the interface of multiple academic fields,...

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The remarkable ecological and demographic success of humanity is largely attributed to our capacity for cumulative culture, with knowledge and technology accumulating over time, yet the social and cognitive capabilities that have enabled cumulative culture remain unclear. In a comparative study of sequential problem solving, we provided groups of capuchin monkeys, chimpanzees, and children with an experimental puzzlebox that could be solved in three stages to retrieve rewards of increasing desirability. The success of the children, but not of the chimpanzees or capuchins, in reaching higher-level solutions was strongly associated with a package of sociocognitive processes—including teaching through verbal instruction, imitation, and prosociality—that were observed only in the children and covaried with performance.