Behaviour 2019
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A primer on the relationship between group size and group performance
Damien Farine1,2,3, Mauricio Cantor2,3,4,5, Lucy Aplin2,6. 1Department of Collective Behaviour, Max Planck Institute of Animal Behavior, Konstanz, , Germany; 2Centre for the Advanced Study of Collective Behaviour, University of Konstanz, Konstanz, , Germany; 3Department of Biology, University of Konstanz, Konstanz, , Germany; 4Department for the Ecology of Animal Societies, Max Planck Institute of Animal Behavior, Konstanz, , Germany; 5Departamento de Ecologia e Zoologia, Universidade Federal de Santa Catarina, Florianopolis, , Brazil; 6Cognitive and Cultural Ecology, Max Planck Institute of Animal Behavior, Radolfzell, , Germany

There is now widespread evidence that larger groups are better at problem-solving. Several hypotheses, such as the pool of competence, have been put forward to explain these patterns. However, identifying the role of hypothesised mechanisms has been challenging, in part because of a lack of clarity on the null hypothesis—the expected relationship between group size and performance at problem solving under the assumption that all individuals have an identical and independent probability of solving. In this talk, we provide an explanation of the nature of the relationship between group size and group performance. We then highlight how group size can have potentially unexpected downstream consequences on group performance—for example on the speed of acquisition of traits—without needing to invoke any complex mechanisms. Finally, we provide guidance on how best to test alternative hypotheses about the relationship between group size and group performance.