'Ruthlessness Gene' Discovered

Researchers at the Hebrew University in Jerusalem found a link between a gene called AVPR1a and ruthless behaviour in an economic exercise called the 'Dictator Game'.

Ebstein and his colleagues decided to look at AVPR1a because it is known to produce receptors in the brain that detect vasopressin, a hormone involved in altruism and 'prosocial' behaviour.

To find out, they tested DNA samples from more than 200 student volunteers, before asking the students to play the dictator game (volunteers were not told the name of the game, lest it influence their behaviour). Students were divided into two groups: 'dictators' and 'receivers' (called 'A' and 'B' to the participants). Each dictator was told that they would receive 50 shekels (worth about US$14), but were free to share as much or as little of this with a receiver, whom they would never have to meet. The receiver's fortunes thus depended entirely on the dictator's generosity.

About 18% of all dictators kept all of the money, Ebstein and his colleagues report in the journal Genes, Brain and Behavior 1. About one-third split the money down the middle, and a generous 6% gave the whole lot away. There was no connection between the participants' gender and their behaviour, the team reports. But there was a link to the length of the AVPR1a gene: people were more likely to behave selfishly the shorter their version of this gene.

It isn't clear how the length of AVPR1a affects vasopressin receptors: it is thought that rather than controlling the number of receptors, it may control where in the brain the receptors are distributed. Ebstein suggests the vasopressin receptors in the brains of people with short AVPR1a may be distributed in such a way to make them less likely to feel rewarded by the act of giving.

I am curious how much difference there was between those with the shorter version of AVPR1a and those with the longer. I found the journal article, but you can only read the abstract for free, so all I found out was:

Participants with short versions (308–325 bp) of the AVPR1a RS3 repeat allocated significantly (likelihood ratio = 14.75, P = 0.001, df = 2) fewer shekels to the ‘other’ than participants with long versions (327–343 bp).

I really don't know what a likelihood ratio, P, or a df mean (if any smart readers out there can explain what this means, please leave a comment).

If your genes can make you more or less altruistic based on how the brain handles vasopressin, I wonder if you will see 'altruism steroids' in the future. There is a nasal spray for oxytocin which is said to increase trust, and oxytocin and vasopressin are very similar. Will we see a nasal spray for vasopressin in the future, with prescriptions for those that are genetically deficient in altruism?

via Nature

Update: This gene is also linked to a propensity for men to skip out on women, or to have marital problems if they do tie the knot.