The modularity of a social group does not affect the transmission speed of a novel, socially learned behaviour, or the formation of local variants

Abstract

The structure of a group is critical in determining how a socially learnt behaviour will spread. Predictions from theoretical models indicate that specific parameters of social structure differentially influence social transmission. Modularity describes how the structure of a group or network is divided into distinct subgroups or clusters. Theoretical modelling indicates that the modularity of a network will predict the rate of behavioural spread within a group, with higher modularity slowing the rate of spread and facilitating the establishment of local behavioural variants which can prelude local cultures. Despite prolific modelling approaches, empirical tests via manipulations of group structure remain scarce. We experimentally manipulated the modularity of populations of domestic fowl chicks, Gallus gallus domesticus, to affect the transmission of a novel foraging behaviour. We compared the spread of behaviour in populations with networks of high or low modularity against control populations where social transmission was prevented. We found the foraging behaviour to spread socially between individuals when the social transmission was permitted; however, modularity did not increase the speed of behavioural spread nor lead to the initial establishments of shared behavioural variants. This result suggests that factors in the social transmission process additional to the network structure may influence behavioural spread.

Keywords: modularity; social structure; social transmission.

Figure 1.

Foraging task apparatus. The novel foraging behaviour required to solve the task involved birds pecking at either the blue (right) or red (left) side to slide the door open in order to access the mealworms behind. Bottom right door opened to reveal well. (Online version in colour.)

Figure 2.

The cumulative probability a bird has of acquiring the solving behaviour in each round when from populations of the high modularity social condition (dark green/triangles), low modularity social condition (light green/squares) and asocial control condition (grey/circles). Ninety-five percentage of confidence intervals shown by coloured bands. (Online version in colour.)

Figure 3.

Social networks of the high (a,b) and low (c,d) modularity populations. Node colours represent an individual's bias in solving technique through a gradient of red (all solves performed were pushing red) to blue (all solves performed were blue), yellow nodes indicate birds that never performed the solving behaviour. Initial seeded demonstrators in each population denoted by ‘D’. Node size is proportional to the total number of solves performed by each bird. (Online version in colour.)