Cognitive performance is linked to group size and affects fitness in Australian magpies

Abstract

The Social Intelligence Hypothesis argues that the demands of social life drive cognitive evolution1–3. This idea receives support from comparative studies linking variation in group size or mating systems with cognitive and neuroanatomical differences across species3–7, but findings are contradictory and contentious8–10. To understand the cognitive consequences of sociality it is also important to investigate social variation within species. Here we show that in wild, cooperatively breeding Australian magpies, individuals living in larger groups show elevated cognitive performance, which in turn is linked to increased reproductive success. Individual performance was highly correlated across four cognitive tasks, hinting towards a “general intelligence factor” underlying cognitive performance. Repeated cognitive testing of juveniles at different ages showed that the group size – cognition correlation emerged in early life, suggesting that living in larger groups promotes cognitive development. Furthermore, we found a positive association between female task performance and three indicators of reproductive success, thus identifying a selective benefit of greater cognitive performance. Together, these results provide critical intraspecific evidence that sociality can shape cognitive development and evolution.

Brainpower boost for birds in large groups

“…Humphrey suggested instead that the complex social dynamics experienced when such animals live in a group become the main selective force driving the evolution of primate intelligence. On page 364, Ashton et al 2 offer support for Humphrey's social-intelligence hypothesis, in a study of wild Australian magpies (Cracticus tibicen dorsalis, also known as…”

“…Social cognition has numerous other manifestations 11,12 . Yet, what Ashton et al 2 tested was essentially non-social cognition. What now begs to be fleshed out is the nature of both the social and non-social intelligence skills that may have been at work in the phenomena these authors observed.…”

“…Cognitive performance and associated reproductive success are now linked to group size in wild magpies. See Letter p.364 2 analysed the relationship between the birds' group size and cognitive performance to test the long-debated idea 1 that life in complex social groups can select for intelligence. At the population level, larger groups of birds performed better than smaller groups in cognitive-performance tests, and cognitive performance was also linked to reproductive success.…”

“…Accordingly, our brains are designed with 'yin-yang' systems that guide our actions and influence our feelings. Neurons in the brain's mesolimbic system promote reward-seeking behaviour and help to process information about actions that result in pleasurable outcomes [1][2][3] . By contrast, neurons in the lateral habenula (LHb) encode information related to noxious outcomes and suppress reward-seeking [4][5][6] .…”

“…Humphrey suggested instead that the complex social dynamics experienced when such animals live in a group become the main selective force driving the evolution of primate intelligence. On page 364, Ashton et al 2 offer support for Humphrey's social-intelligence hypothesis, in a study of wild Australian magpies (Cracticus tibicen dorsalis, also known as Gymnorhina tibicen dorsalis).The causal relationships between social complexity, intelligence and reproductive success proposed by Humphrey inspired a generation of primatologists, who uncovered unexpected sophistication in monkeys' and apes' social knowledge and political manoeuvrings [3][4][5] . However, these discoveries arguably made it difficult to test Humphrey's hypothesis directly, because intelligenceboth in social interactions and in non-social realms, such as foraging or tool use -and social complexity were revealed to be composed of many components 4,5 .…”