The usual approach in livestock genetic improvement is to consider the phenotype as a sum of a heritable component and a residual non-genetic component, referred to as environment, P = A + E. However, when individuals are kept in groups, the environment that an individual experiences contains a social component due to its group members. In contrast to the physical environment, this social component may have a heritable basis and therefore respond to selection. Thus, for traits affected by social interactions among individuals, current selection strategies can be improved by including the social effects of individuals in the selection decisions. Here we present some basic theory for improving traits affected by interactions, and first empirical results in three populations of layer chickens.