Quorum responses and consensus decision making

Abstract

Animal groups are said to make consensus decisions when group members come to agree on the same option. Consensus decisions are taxonomically widespread and potentially offer three key benefits: maintenance of group cohesion, enhancement of decision accuracy compared with lone individuals and improvement in decision speed. In the absence of centralized control, arriving at a consensus depends on local interactions in which each individual's likelihood of choosing an option increases with the number of others already committed to that option. The resulting positive feedback can effectively direct most or all group members to the best available choice. In this paper, we examine the functional form of the individual response to others' behaviour that lies at the heart of this process. We review recent theoretical and empirical work on consensus decisions, and we develop a simple mathematical model to show the central importance to speedy and accurate decisions of quorum responses, in which an animal's probability of exhibiting a behaviour is a sharply nonlinear function of the number of other individuals already performing this behaviour. We argue that systems relying on such quorum rules can achieve cohesive choice of the best option while also permitting adaptive tuning of the trade-off between decision speed and accuracy.

Leadership, consensus decision making and collective behaviour in humans

“…They are very important for both animal and human groups as they allow groups to remain together despite individual differences in preference and consequently help prevent individuals from losing the benefits associated with being part of a large group (Conradt & Roper 2009;Sumpter & Pratt 2009). Decision making almost always involves some form of leadership.…”

The effect of individual variation on the structure and function of interaction networks in harvester ants

“…The speed of information flow on a social insect network can determine how fast a colony responds to stimuli and achieves a collective decision [35]. For example, in the rock ant, Temnothorax albipennis, the more individuals visit the location of a new nest site, the higher the recruitment to the new nest, the more information about the nest's location arrives at the nest, and the faster the colony will move into it, thus decreasing exposure to the danger associated with emigration [36].…”

Hysteretic dynamics of active particles in a periodic orienting field

“…The loop area is related to both the 'persistence' of the group's motion (dynamic remanence-the amount of drift after the field is removed) and its 'stubbornness' (dynamic coercivity-the field magnitude required to revert the motion of the group). For example, these observations can be interpreted in terms of opinion dynamics [13,16,[46][47][48], where the consensus can be associated with the aligned state with a non-zero order parameter, while the alternating field would model the frequent contradictory stimuli. Our results suggest that the prominent social (aligning) interactions can enhance the persistence of the group's opinion at relatively low signal frequencies, while frequent contradictory signals prevent the development of a collective response.…”

“…The level of consciousness of the individuals apparently plays a minor role in the large-scale dynamics as the same principles of self-organization that govern the dynamics of groups of animals or cells apply to human social phenomena, traffic, robotics and decisionmaking [11][12][13][14][15][16][17]. One of the best-studied collective dynamics phenomena is the onset of globally aligned motion in active swarms [18][19][20][21][22][23][24][25][26][27][28].…”