When in Rome ... An evolutionary perspective on conformity

Is proportion as important as group size when exploring conformity in small groups? Two tests of Boyd and Richerson’s (1985) conformist transmission model were undertaken. In experiment one, 378 individuals were observed in a computer laboratory. A rare behaviour was modelled by a number of naive models. As each individual entered the laboratory the proportion of models of the behaviour and the behaviour of the newcomer was recorded. In experiment two, 476 participants in psychology experiments took part (unknowingly) in an additional experiment where both proportion and group size were manipulated. Logistic regression indicated that the proportion of models, but not group size, was a significant predictor of conformity in both experiments. The findings are discussed in terms of their contribution to an evolutionary theory of human cooperative behaviour.