Shared decision-making drives collective movement in wild baboons

Abstract

Conflicts of interest about where to go and what to do are a primary challenge of group living. However, it remains unclear how consensus is achieved in stable groups with stratified social relationships. Tracking wild baboons with high-resolution GPS and analyzing their movements relative to one another reveals that a process of shared decision-making governs baboon movement. Rather than preferentially following dominant individuals, baboons are more likely to follow when multiple initiators agree. When conflicts arise over the direction of movement, baboons choose one direction over the other when the angle between them is large, but compromise if not. These results are consistent with models of collective motion, suggesting that democratic collective action emerging from simple rules is widespread, even in complex, socially-stratified societies.

Evaluating reproductive decisions as discrete choices under social influence

“…Number of imitators would then be analogous to social influence in our model, in which the social pay-off is proportional to the product of the social-learning parameter and the difference in popularity between the two choices (electronic supplementary material, appendix). As shown in figure 2, we see a correspondence between Strandburg-Peshkin et al's [27] directional agreement and our transparency and between their number of initiators and our strength of social influence. Both approaches find the highest predictability of following in the northeast corner, where leadership is transparent [28].…”

“…(a) Field data among wild baboons [27] showing directional agreement among initiators of movement on the vertical axis and the number of initiators on the horizontal axis. (b) A contour plot in the framework of figure 1, showing the maximum fitness for three choices when that fitness is defined as a function of both the inherent utility of the choice and its social popularity [28].…”

The wisdom of crowds for visual search

“…group decision rules | signal detection theory | ideal observer analyses | wisdom of crowds G roups of insects (1)(2)(3)(4), fish (5-7), birds (8)(9)(10), mammals (11)(12)(13)(14), and primates (15)(16)(17)(18) have been shown to aggregate their individual judgments into group decisions for various tasks (19,20). Although some groups seem to have leaders who make decisions alone on behalf of their groups (17,(21)(22)(23), it is difficult for individuals to outperform even simple aggregations of the entire group's individual judgments (4,7,9,10,19,(24)(25)(26).…”

Démocratie, compromis et consensus dans les déplacements collectifs chez le babouin

“…Mais ces mêmes règles peuvent-elles s'appliquer à un groupe d'animaux plus hiérarchisé comme celui des babouins (Papio anubis) ? C'est cette intéressante problématique que des chercheurs de l'université de Davis, en Californie, ont récemment approfondie au centre de recherche Mpala au Kenya [3]. Cette étude, qui a fait la couverture du prestigieux magazine Science, innove par sa méthodologie, permettant pour la première fois de modéliser avec précision les dynamiques de déplacements et les déci-sions collectives d'un groupe de primates dans son milieu naturel.…”