Neural basis of social decision making

Alan G. Sanfey & James K. Rilling, University of Arizona & Emory University

In:- Neuroscience of Decision Making  –  Eds:- Oshin Vartanian & David Mandel  –  Psychology Press  –  Taylor & Francis Group

The research can be taken to set a query against the attempt to create an orthodoxy that treats dislike of unfairness as part of an illusion of freewill.  The studies show perceived unfairness as leading to increased activity in brain regions such as the anterior insula, the caudate nucleus and the nucleus accumbens, and linking to the emotion-related orbitofrontal, a brain region in parts of which activity is correlated to subjective experience.

The brain is able to process alternative choices for behaviour and choose an optimal behaviour in the face of uncertainty, including uncertainties involved in social interactions. The authors’ studies have particularly observed neural responses to perceived unfairness.

One brain region, the anterior part of the insula, was demonstrated to show increased activity as unfairness was perceived to increase. There was also a higher degree of activation when the unfairness originated from human as opposed to computerised behaviour. Activity in the anterior insula was predictive of whether a financial offer would be accepted or rejected. In situations where one subject cooperated, but this was not reciprocated by another party, there was activity in the anterior insula, and connections between this and the orbitofrontal predicted a withdrawal of the first subject’s cooperation.

The anterior insula region which responds to unfairness is the same brain region that responds to physical pain and disgust, and which maps physiological body states such as touch and visceral responses. The interaction of the anterior insula and limbic related areas such as the orbitofrontal may be relevant to unpleasant social interactions.

The striatum, which is the input region of the basal ganglia, has been shown to track the degree of reciprocation to cooperative behaviour. Positive or negative emotions resulting from reciprocation or non-reciprocation may be encoded in this area. Reciprocation by another subject is seen to lead to increased activity in the caudate nucleus and nucleus accumbens regions of the basal ganglia. Where cooperation and reciprocation is repeated these regions may have a system of prediction errors, in which expected reciprocation is compared with actual reciprocation. Studies also showed activity relative to a willingness to punish non-cooperators even where there was a cost to doing so.


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