Collective Sensing and Decision-Making in Animal Groups: From Fish Schools to Primate Societies

Understanding how social influence shapes biological processes is a central challenge in contemporary science, essential for achieving progress in a variety of fields ranging from the organization and evolution of coordinated collective action among cells, or animals, to the dynamics of information exchange in human societies. Using an integrated experimental and theoretical approach I will address how, and why, animals exhibit highly-coordinated collective behavior. A major limitation in the study of large animal groups is that it has not been possible to observe directly the pathways of communication, and social networks are typically based on proxies [1]. I will demonstrate new imaging technology that allows us to reconstruct (automatically) the dynamic, time-varying networks that correspond to the visual cues employed by organisms when making movement decisions. Sensory networks are shown to provide a much more accurate representation of how social influence propagates in groups [2], and their analysis allows us to identify, for any instant in time, the most socially-influential individuals within groups, and to predict the magnitude of complex behavioral cascades at the moment of their initiation, before they actually occur [3]. I will also investigate the coupling between spatial and information dynamics in groups and reveal that emergent problem solving is the predominant mechanism by which mobile groups sense, and respond to complex environmental gradients [4]. This distributed sensing requires rudimentary cognition and is shown to be highly robust to noise. Evolutionary modeling demonstrates such behavior readily evolves within populations of selfish organisms, allowing individuals to compute collectively the spatial distribution of resources and to allocate themselves effectively among distinct, and distant, resource patches, without requiring information about the number, location or size of patches. Finally I will reveal the critical role uninformed individuals (those who have no information about the feature upon which a collective decision is being made) play in fast, and effective, democratic consensus decision-making in collectives [5,6] and will test these predictions with experiments involving schooling fish [6] and wild baboons [7].

1. Couzin, I.D. (2007) Collective minds. Nature 455, 715.

2. Strandburg-Peshkin, A., Twomey, C.R., Bode, N.W., Kao, A.B., Katz, Y., Ioannou, C.C., Rosenthal, S.B., Torney, C.J., Wu, H., Levin, S.A. & Couzin, I.D. (2013) Visual sensory networks and effective information transfer in animal groups, Current Biology 23(17), R709-711.

3. Rosenthal, S.B., Twomey, C.R., Hartnett, A.T., Wu, H.S. & Couzin, I.D. (2015) Revealing the hidden networks of interaction in mobile animal groups allows prediction of complex behavioral contagion, PNAS 112(15), 4690-4695.

4. Berdahl, A., Torney, C.J., Ioannou, C.C., Faria, J. & Couzin, I.D. (2013) Emergent sensing of complex environments by mobile animal groups, Science 339(6119) 574-576.

5. Couzin, I.D., Krause, J., Franks, N.R. & Levin, S.A. (2005) Effective leadership and decision making in animal groups on the move. Nature 433, 513-516.

6. Couzin, I.D., Ioannou, C.C., Demirel, G., Gross, T., Torney, C.J., Hartnett, A., Conradt, L., Levin, S.A. & Leonard, N.E. (2011) Uninformed individuals promote democratic consensus in animal groups. Science 334(6062) 1578-1580.

7. Strandburg-Peshkin, A., Farine, D.R., Couzin, I.D. & Crofoot, M.C. (2015) Shared decision-making drives collective movement in wild baboons. Science 348(6241), 1358-1361