Saturday, July 14, 2012

David Berreby - Altrusim Linked to Empathy Circuitry in the Brain

Writing in the Mind Matters column at Big Think, David Berreby offers a brief overview of the findings in a new study suggesting altruism is linked to the same brain circuitry (the right temporoparietal junction) as moral decision making and empathy.

[For more on the link to empathy, see Jean Decety's work in this area, including this 2007 article (Neuroscientist; 13; 580) that outlines the role of the right temporoparietal junction in social interactions - he examines how lower-level computational functions are essential to the meta-cognitive processes of self/other distinction, agency, and empathy.]

The study is pay-walled, so here is that material available at Neuron's site. Berreby has not read the full paper yet either, but his knowledge of the neuroscience allows him to comment on the study in general.
  • Econometric evidence reveals large individual differences in behavioral altruism
  • Gray matter volume in the right TPJ predicts subjects' behavioral altruism
  • GM in right TPJ predicts functional activity profile in TPJ during altruistic choice
  • Individual differences in altruism relate to both structure and function of right TPJ


Human altruism shaped our evolutionary history and pervades social and political life. There are, however, enormous individual differences in altruism. Some people are almost completely selfish, while others display strong altruism, and the factors behind this heterogeneity are only poorly understood. We examine the neuroanatomical basis of these differences with voxel-based morphometry and show that gray matter (GM) volume in the right temporoparietal junction (TPJ) is strongly associated with both individuals' altruism and the individual-specific conditions under which this brain region is recruited during altruistic decision making. Thus, individual differences in GM volume in TPJ not only translate into individual differences in the general propensity to behave altruistically, but they also create a link between brain structure and brain function by indicating the conditions under which individuals are likely to recruit this region when they face a conflict between altruistic and selfish acts.
As Berreby points out, "None of this means that Morishima et al. have proved that some people are born selfish while others are destined by their brains for sainthood." Based on what we know about how brain circuitry develops, the likelier explanation is that the more altruistic people have learned that behavior from infancy forward, thus re-enforcing those behaviors.

Study: The More Altruistic You Are, The Bigger Will Be This Part of Your Brain

File_vertebrate-brain-regions.png%20-%20wikimedia%20commonsIn pursuit of the biological basis of morality, researchers are interested in an area of the brain at the boundary of the right temporal lobe and the right parietal lobe (very roughly, it's located maybe 2 inches above the midpoint of a line between your right eyebrow and your right ear, not that I recommend digging around for it). This right temporoparietal junction has been linked in various ways to moral judgments about the self and others. Now this paper, out today in the journal Neuron, supplies some striking new evidence for this area's importance. In lab experiments, people with more brain cells in this region were more altruistic than people with fewer.

Yosuke Morishima and his co-authors ran a functional MRI scan of their volunteers at the University of Zurich as they allocated a sum of money between themselves and an anonymous second person. (By the way, "Yosuke," for an altruism researcher, is an aptonym. It's a name that means "to give help" or "great support.") Some of the participants were quite selfish, while others were much more altruistic, giving up a meaningful amount of cash for another person whom they did not know. And it turned out the volunteer's degree of altruism correlated with the amount of gray matter they possessed at the right temporoparietal junction ("gray matter" consists of neurons (the cells whose activity makes brains brains) as well as the glial cells that support them and their blood supply).

I haven't yet read the paper (it's paywalled and I can't get to the library today to obtain it). So I can't report how many subjects were involved, nor whether the correlation was a statistical average or an absolutely reliable predictor for each individual ("more gray matter equals more altruism"). I'll come back to this post to clarify after I get the paper itself.

Still, I think I'm safe in saying this is an exciting result, because no one has yet shown such a strong link between a physical brain measurement and the complex behavior of giving someone a lift at cost to one's self. Maybe this isn't the biological basis of morality (you can argue, for example, that deciding to give money to a stranger is a way of building up your prestige, or promoting an "one-for-all" ethos that will protect you). But it is, strictly speaking, altruism (I take less than I could so you can get more).

None of this means that Morishima et al. have proved that some people are born selfish while others are destined by their brains for sainthood. As they've said themselves, the authors can't say whether anatomy causes behavior, or behavior causes anatomy. Maybe people born with bigger right temporoparietal regions are more inclined to be unselfish. But it's equally possible that unselfishness makes people use the region more, so that it beefs up like the muscles of a gym rat.

What is significant, though, is the pinpointing of a specific connection between the anatomy of the brain and the complex decisions of the mind.

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