title: Social information use and the evolution of unresponsiveness in collective systems.
abstract: Animal groups in nature often display an enhanced collective information-processing capacity. It has been speculated that natural selection will tune this response to be optimal, ensuring that the group is reactive while also being robust to noise. Here, we show that this is unlikely to be the case. By using a simple model of decision-making in a dynamic environment, we find that when individuals behave rationally and are subject to selection based on their accuracy, optimality of collective decision-making is not attained. Instead, individuals overly rely on social information and evolve to be too readily influenced by their neighbours. This is due to a classic evolutionary conflict between individual and collective interest. The result is a sub-optimal system that is poised on the cusp of total unresponsiveness. Individuals in the evolved group exhibit delayed reactions to changes in the environment, before responding with rapid, socially reinforced transitions, reminiscent of familiar human and animal social systems (markets, stampedes, fashions, etc.). Our results demonstrate that behaviour of this type may not be pathological, but instead could represent an evolutionary attractor for such collective systems.
authors.affiliation: Centre for Mathematics and the Environment, University of Exeter, Penryn Campus, Cornwall, UK Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, USA colin.j.torney@gmail.com.
authors.forename: Colin J
authors.initials: CJ
authors.lastname: Torney
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 06, UMR 7598, Laboratoire Jacques-Louis Lions, Paris 75005, France Laboratoire Jacques-Louis Lions, CNRS, UMR 7598, Paris 75005, France INRIA-Paris-Rocquencourt, EPC MAMBA, Domaine de Voluceau, BP105, 78153 Le Chesnay Cedex, Paris, France.
authors.forename: Tommaso
authors.initials: T
authors.lastname: Lorenzi
authors.affiliation: Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, USA.
authors.forename: Iain D
authors.initials: ID
authors.lastname: Couzin
authors.affiliation: Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, USA.
authors.forename: Simon A
authors.initials: SA
authors.lastname: Levin
mesh_terms: D000818:Animals; D003657:Decision Making; D006801:Humans; D008962:Models, Theoretical; D012919:Social Behavior
keywords: collective behaviour; evolution; social information