Speaker
Description
No two individuals are alike. Even individuals of the same sex, age, size and social background tend to differ consistently in temperament, motivation, cognition and behaviour. In virtually all species studied, ranging from spiders to sticklebacks and from octopuses to chimpanzees, individuals differ systematically in whole suites of correlated behaviours. For example, one often finds stable differences in aggressiveness, and aggressive individuals tend to differ from non-aggressive conspecifics in a multitude of ways: they are bolder, more explorative, less philopatric, less ‘social’ (but not necessarily less cooperative), have a lower learning performance, and exhibit less parental care. The existence of such ‘personalities’ (also termed behavioural syndromes, coping styles or temperaments) provides a challenge for evolutionary theory. First, why do different personality types stably coexist? Should we not expect a single optimal phenotype? Second, why are behavioural differences consistent over extended periods of time? Should we not expect a more flexible structure of behaviour that is fine-tuned to the local circumstances? And third, why are quite different types of traits correlated, and why are similar correlations observed in very different taxa? Should we not expect pronounced differences in the behavioural architecture of molluscs, insects and mammals, reflecting the differences in their physiology, life history and ecology?
Evolutionary game theory can cope relatively easily with the first two challenges. Behavioural polymorphism can be explained by diversifying frequency-dependent selection or condition-dependent strategies (where individuals differ subtly in ‘condition’). Time consistency can be explained by positive feedbacks (such as training effects) that make regularly performed behaviours more efficient or less costly. I will focus on the third challenge and discuss various (adaptive and non-adaptive) explanations for frequently observed behavioural correlations. This challenge is a serious one, as it undermines the standard approach of evolutionary game theory. Game theorists are used to studying different types of behaviour in isolation. But does it make sense to investigate aggressive behaviour, foraging behaviour, mating behaviour, and parental behaviour in independent game models if these behaviours are intrinsically linked via the structure of personalities? To what extent is it possible to incorporate ‘personality thinking’ into the framework of evolutionary game theory?
