Interacting personalities: behavioural ecology meets quantitative genetics

• Individuals vary in their response to phenotypes of conspecifics.
• Social responsiveness research is key to behavioural ecology and quantitative genetics.
• A reaction-norm framework integrates personality and social responsiveness research.
• Social responsiveness must incorporate the multilevel nature of behaviour.

Behavioural ecologists increasingly study behavioural variation within and among individuals in conjunction, thereby integrating research on phenotypic plasticity and animal personality within a single adaptive framework. Interactions between individuals (cf. social environments) constitute a major causative factor of behavioural variation at both of these hierarchical levels. Social interactions give rise to complex ‘interactive phenotypes’ and group-level emergent properties. This type of phenotype has intriguing evolutionary implications, warranting a cohesive framework for its study. We detail here how a reaction-norm framework might be applied to usefully integrate social environment theory developed in behavioural ecology and quantitative genetics. The proposed emergent framework facilitates firm integration of social environments in adaptive research on phenotypic characters that vary within and among individuals.