Approach, avoidance, and their conflict: The problem of anchoring

To understand the neurobiology of individual differences in approach and avoidance behaviour, we must anchor constructs at the behavioural level to the long-term global sensitivities of the neural systems that give rise to the observed stable patterns of behaviour. We will argue that this requires not only appropriate data at both the neural and behavioural levels but also appropriate account to be taken of interactions at the intervening level of the conceptual nervous system (Hebb, 1949; Gray, 1975). In particular, in accounting for approach and avoidance behaviour we must include consideration of the distinction between valuation and motivation (Corr and McNaughton, 2012), of interactions between the approach system and the avoidance system (Gray and Smith, 1969), and of their interaction with a distinct additional system that is activated by approach-avoidance conflict (Gray, 1977; summarised in Corr, 2013). But first we need to ask why would we expect there to be traits linked to global approach and avoidance systems? Simple animals (with little or no brain) can produce approach and avoidance behaviour (towards benefits and ultimately reproduction; and away from dangers and ultimately failure to reproduce) via multiple independent rules of thumb (Krebs et al., 1983). But we can expect more complex brains to have largely integrated these simple elements into systems more generally dedicated to approach or avoidance “because this is how [a few] genes can build a complex system that will produce appropriate but flexible behaviour to increase fitness. … Rather than just pre-programmed movements such as tropisms and taxes, … if the genes are efficiently to control behaviour … they must specify the goals for action.” (Rolls, 2000, p. 190, p. 183). Together with the evolution of general approach and avoidance systems that are not tied to any specific motivating stimulus (reinforcer), we would expect evolution of the long-term adaptive control of their overall sensitivity to adequate inputs. Such stable sensitivity would be the neurobiological basis of approach and avoidance personality traits. Determining the appropriate neurobiological measure for the sensitivity of a highly evolved approach or avoidance system is not simple. These systems have hierarchically organised neural levels with processing ranging from “quick and dirty” to “slow and sophisticated” for both perception (LeDoux, 1994) and action (Graeff, 1994; 2010). Sensitivity to input determines which level of the system is activated and so sensitivity cannot reside in any one of the modules