Information transmission via movement behaviour improves decision accuracy in human groups

<p>A major advantage of group living is increased decision accuracy. In animal groups information is often transmitted via movement. For example, an individual quickly moving away from its group may indicate approaching predators. However, individuals also make mistakes which can initiate information cascades. How responsive should individuals then be to escaping group members? Increasing responsiveness increases true positives (i.e. escape when a predator is present) but at the cost of increased false positives (i.e. escape when a predator is absent). Conversely, reducing responsiveness decreases not only false positives but also true positives, resulting in a fundamental trade-off in decision accuracy. Here we investigated how socially responsive individuals are to information transmission via movement. We performed a simulated predator detection task using human groups in which humans stepped forward if they wanted to escape. We confirm that this simple movement mechanism allows individuals in groups to simultaneously increase true positives and decrease false positives. The increase in the number of escapees over time during collective decisions depended on the personal information of the group members. Individual predator detection by only a few group members rarely resulted in anyone stepping forward. Individual predator detection by a quarter of the group often resulted in the entire group escaping. Finally, individual predator detection by at least half of the group led to a rapid escape of the whole group. Overall, the increase in the number of escapees over time followed a linear response. Since information transmission via movement is widespread in animal groups, this mechanism is expected to be relevant for many animal groups to improve decision accuracy.