EFFECTS OF SOCIAL GROUP-SIZE ON INFORMATION-TRANSFER AND TASK ALLOCATION

Social animals exchange information during social interaction. The rat e of interaction and, hence, the rate of information exchange, typical ly changes with density and density may be affected by the size of the social group. We investigate models in which each individual may be e ngaged in one of several tasks. For example, the different tasks could represent alternative foraging locations exploited by an ant colony. An individual's decision about which task to pursue depends both on en vironmental stimuli and on interactions among individuals. We examine how group size affects the allocation of individuals among the various tasks. Analysis of the models shows the following. (1) Simple interac tions among individuals with limited ability to process information ca n lead to group behaviour that closely approximates the predictions of evolutionary optimality models, (2) Because per capita rates of socia l interaction may increase with group size, larger groups may be more efficient than smaller ones at tracking a changing environment, (3) Gr oup behaviour is determined both by each individual's interaction with environmental stimuli and by social exchange of information. To keep these processes in balance across a range of group sizes, organisms ar e predicted to regulate per capita rates of social interaction and (4) Stochastic models show, at least in some cases, that the results desc ribed here occur even in small groups of approximately ten individuals .