Consciousness Blog 15 July 2012

A team of researchers at the University of Zurich has shown a strong association between altruistic behaviour and the size of the TPJ (right temporo parietal junction) in human subjects.

It has been known for a long time that the TPJ, at the junction of the parietal and temporal lobes, is involved in Theory of Mind (awareness of other people's mental states) but this is the first time that a direct causal link has been both demonstrated and measured.

Specifically, Ernst Fehr, Director of the Department of Economics, and four colleagues measured the quantity of grey matter in the TPJs in their 30 subjects using voxel-based morphometry, and compared the results with the behaviour of the subjects in a series of situations offering opportunities for altruism. The degree of altruism shown occupied a very wide spectrum.

“The structure of the TPJ strongly predicts an individual’s set point for altruistic behavior, while activity in this brain region predicts an individual’s acceptable cost for altruistic actions,” reports lead author Yosuke Morishima of the Laboratory for Social and Neural Systems Research at the University.

One interesting sidelight was that sense of fairness was strongly implicated in the results: people were much more likely to be altruistic if the results of their altruism were to narrow rather than widen disparities in comparative wealth (in terms of the game being played). But such differences did not affect the overall link between TPJ volume and degree of altruism.

Ernst Fehr adds: "These are exciting results for us. However, one should not jump to the conclusion that altruistic behavior is determined by biological factors alone. The volume of gray matter is also influenced by social processes." Although there seems likely to be a strong genetic component in TPJ volume, Fehr points out that the brain retains considerable plasticity during individual social development; thus appropriate training or social norms may impact both on thhe volume of TPJ grey matter and hence on altruistic behaviour, subconscious though its springs may be.

The expansion and growing sophistication of the human brain is strongly associated with the development of group living; and new methods of brain research have expanded our understanding of the high degree of functional specialization exhibited in the brain. So there will be little surprise that one particular part of the brain should have such a precisely observable role in social relationships.

But what about animals? The TPJ is not peculiar to humans; as a morphological formation it exists in all mammals, and had precursors in reptiles. Theory of Mind has been attributed variously to apes, elephants, dolphins and dogs among other species. Much recent research has emphasized the continuity of brain evolution, and has shown that many of the faculties which we like to believe make us human have their origins way back in evolution. Rather than testing animals for human-type altruistic behaviour, perhaps we should be looking to correlate other types of animal social behaviour with TPJ volume? It probably didn't originate in connection with Theory of Mind.

Read more in Chapter One of Agent Human by Michael Bell, The Origins and Purpose of Consciousness.


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