Leadership, consensus decision making and collective behaviour in humans

Abstract

This paper reviews the literature on leadership in vertebrate groups, including recent work on human groups, before presenting the results of three new experiments looking at leadership and decision making in small and large human groups. In experiment 1, we find that both group size and the presence of uninformed individuals can affect the speed with which small human groups (eight people) decide between two opposing directional preferences and the likelihood of the group splitting. In experiment 2, we show that the spatial positioning of informed individuals within small human groups (10 people) can affect the speed and accuracy of group motion. We find that having a mixture of leaders positioned in the centre and on the edge of a group increases the speed and accuracy with which the group reaches their target. In experiment 3, we use large human crowds (100 and 200 people) to demonstrate that the trends observed from earlier work using small human groups can be applied to larger crowds. We find that only a small minority of informed individuals is needed to guide a large uninformed group. These studies build upon important theoretical and empirical work on leadership and decision making in animal groups.

Videos

1) The 20 informed individuals were wearing turquoise baseball caps and were trying to reach target 4 (out of shot on the centre right). The group quickly became stretched out towards the target as the informed individuals positioned themselves at the edge of the group closest to their target. After 75seconds the whole group reached the target of the informed individuals without splitting.

2) The 20 informed individuals (wearing purple baseball caps) quickly reached their target (number 5, slightly to the left at the top of the shot) and within 60 seconds had taken approximately half of the group with them. The group then proceeded to become stretched out across the arena as the 10 informed individuals (wearing yellow baseball caps) attempted to reach their target (number 11, directly opposite the target of the 20). After approximately 110 seconds they had also reached their target and managed to take at least 40% of the group with them. A bridge of people remained between the 2 targets with a constant oscillation of people between the 2 targets.

3) Interestingly, lane formation in a torus as observed in our experiment has never been described from animal groups. In fish and bats it is unlikely to arise because of the turbulence that opposing lanes would produce which would increase energy expenditure. However, lane formation (though not in a torus context) is well described in ants (Couzin & Franks 2003; Dussutour et al. 2004, 2005) where just like in humans (Helbing & Molnar 1995; Helbing et al 2001) it is unlikely to increase locomotion costs.

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