Altruistic brains, more or less

Research published in the journal Neuron last week may help to explain why some individuals are more altruistic than others. Experts at the University of Zurich in Switzerland carried out an experiment based on the hypothesis that the temporoparietal junction (TPJ) – a region of the brain previously associated with the ability to understand another’s feelings, motives or beliefs – might be associated with the level of altruism expressed by an individual.

While the term empathy refers to affective experience of another person's affective state (and may affect altruistic behaviour towards the other person due to empathetic concern), showing high levels of empathy does not always increase altruism.

Participants in the experiment had their brain scanned as they played a game which involved dividing money between themselves and an anonymous partner. It was discovered that the more generous players had a larger TPJ in their right hemisphere than those who made less generous decisions.

Not only was brain structure correlated with the extent of an individual’s altruism, but activity in the TPJ was found to be linked to the ease or difficulty which ease subject had in making specific decisions based on the personal cost of an altruistic act.

Dr Yosuke Morishima from the Department of Economics at the University of Zurich, who led the study, spoke to ScienceOmega.com about the not-entirely-expected results and the potential of neurobiology to explain the nature of human altruism.

Did you expect to find differences between individuals in the brain structure involved in altruism?
We did not expect that we would find such a strong association, but this effect was confirmed in our follow-up experiments, which has convinced us of the significance of the findings.

What techniques did you use to establish the link between structure and function?
We used magnetic resonance imaging (MRI) – one of the most widely used non-invasive brain imaging methods – to acquire structural images of the brain and measure functional activation. We particularly used a method called voxel-based brain photometry to quantify the individual amount of grey matter (where neuronal cells exist) in regions of interests.

We found that grey matter volume in the right brain hemisphere of the temporoparietal junction (TPJ) – an area of the brain associated with empathy or moral reasoning – is correlated with behavioural altruism. To establish the link between structure and function we focused on the same brain area and investigated functional activation when the subject decided to give some money to an anonymous player in the experiments. We found that functional activation profiles in that region are predicted by individual differences in behavioural altruism, predicted by individual variation in brain structure. So far we believe we have established a link between functional and structural variations for altruistic acts.

To what extent is the human brain hardwired (or not) for altruism, and to what extent can we train ourselves to be more altruistic?
Our behaviour is highly dependent on given contexts. Even selfish people might help others if they are really deserving of help. However, such selfish people would behave selfishly in general, so that individuals have their own set point for committing altruistic acts. We found the neurobiological accounts for the line between the set point of altruistic acts (structure) and context-dependent altruism (functional activation).

Although we don't expect we can necessarily train our brains in such a way that we become more altruistic, it might be possible for young kids. However, we have no idea as yet how you would go about training the brain for this.

Could neurobiology explain why human altruism extends beyond genetically related individuals?
We still don't have a clear answer to this question. To underpin the question, we need to measure brain activity not only from humans, but also from non-human primates, such as monkeys or gorillas. However, I personally am of the opinion that our brain capacity co-evolved with cultural developments.

This would be termed bidirectional influence: development of the brain allows it to handle more complex information and complex information demands brain capacity, presumably combined with the effects of natural selection. During that process, temporally and spatially separate information, ie interaction with society, is taken into account.

In the real world, helping others would increase the good reputation of the helper and this good reputation would benefit the helper in the long run (but not always). Such an interaction is called indirect reciprocity. I assume indirect reciprocity-driven behaviour is embedded in our behavioural sets. However, the degree of implementation would be varied among individuals and this variation is exactly what we have found in the current study.

How do responses change according to whether inequality for an individual was advantageous or disadvantageous?
We found people behave less altruistically when their payoff is less than that of others. I think this is consistent with our intuitions. We also examined brain regions associated with the altruism parameter in the domain of disadvantageous situations, but we did not find any area to be particularly significant.