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.

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Social intelligence, innovation, and enhanced brain size in primates

Humans are unique in their range of environments and in the nature and diversity of their behavioral adaptations. While a variety of local genetic adaptations exist within our species, it seems certain that the same basic genetic endowment produces arctic foraging, tropical horticulture, and desert pastoralism, a constellation that represents a greater range of subsistence behavior than the rest of the Primate Order combined. The behavioral adaptations that explain the immense success of our species are cultural in the sense that they are transmitted among individuals by social learning and have accumulated over generations. Understanding how and when such culturally evolved adaptations arise requires understanding of both the evolution of the psychological mechanisms that underlie human social learning and the evolutionary (population) dynamics of cultural systems.

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The Evolution of Cultural Evolution

The widely held hypothesis that enlarged brains have evolved as an adaptation to cope with novel or altered environmental conditions lacks firm empirical support. Here, we test this hypothesis for a major animal group (birds) by examining whether large-brained species show higher survival than small-brained species when introduced to nonnative locations. Using a global database documenting the outcome of >600 introduction events, we confirm that avian species with larger brains, relative to their body mass, tend to be more successful at establishing themselves in novel environments. Moreover, we provide evidence that larger brains help birds respond to novel conditions by enhancing their innovation propensity rather than indirectly through noncognitive mechanisms. These findings provide strong evidence for the hypothesis that enlarged brains function, and hence may have evolved, to deal with changes in the environment.

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Big brains, enhanced cognition, and response of birds to novel environments.

https://research.amnh.org/users/rfr/soletal.pdf

Behavioural flexibility and invasion success in birds

Several comparative research programs have focused on the cognitive, life history and ecological traits that account for variation in brain size. We review one of these programs, a program that uses the reported frequency of behavioral innovation as an operational measure of cognition. In both birds and primates, innovation rate is positively correlated with the relative size of association areas in the brain, the hyperstriatum ventrale and neostriatum in birds and the isocortex and striatum in primates. Innovation rate is also positively correlated with the taxonomic distribution of tool use, as well as interspecific differences in learning. Some features of cognition have thus evolved in a remarkably similar way in primates and at least six phyletically-independent avian lineages. In birds, innovation rate is associated with the ability of species to deal with seasonal changes in the environment and to establish themselves in new regions, and it also appears to be related to the rate at which lineages diversify. Innovation rate provides a useful tool to quantify inter-taxon differences in cognition and to test classic hypotheses regarding the evolution of the brain.

/pdf/brains-innovations-and-evolution-in-birds-and-primates-6nkg6zf79d.pdf

Brains, innovations and evolution in birds and primates.

Many authors have proposed that behavioural flexibility in the field is associated with learning ability in captivity, relative forebrain size and rate of structural evolution. In birds, the frequency of feeding innovations reported in the short notes sections of ornithology journals may be a good way to operationalize flexibility. In this paper, we examine in the birds of Australia and New Zealand the relationship between forebrain size and innovation frequency found in a previous study covering North America and the British Isles. From a methodological point of view, the two variables are highly reliable: innovation frequency per taxonomic group is similar when different readers judge innovation reports and when different editorial styles govern journals; relative forebrain size yields very similar estimates whether mean residuals from a log-log regression are used or ratios of forebrain to brainstem mass. Innovation frequency per taxon is correlated between the two Australasian zones and between these zones and the more northerly ones studied previously. Innovation frequency is also associated with relative forebrain size in Australia and, to a lesser extent, in New-Zealand; in Australia, parrots show the high frequency of innovations predicted by their large forebrain, but yield no innovations in the New Zealand sample. The forebrain/innovation trend is independent of juvenile development mode, but phylogeny appears to be an important intervening variable in Australasia, as evidenced by non-significant independent contrasts.

Sherry Dawson

Papers

Feeding innovations and forebrain size in Australasian birds