Genetic programming to be generous?

 

Jerusalem, Israel. Are those inclined towards generosity genetically programmed to behave that way? A team of researchers, including Dr. Ariel Knafo of the Psychology Department at The Hebrew University of Jerusalem, believes that this could very well be the case.

 

Researchers constructed a controlled experiment, an online task, that involved a choice of whether or not participants would give away their money.

 

The research team found that those who chose to give away some or all of their money differed genetically from those involved in the exercise who chose not to give their money away.

The scientists conducted the experiment with 203 online "players". Each player could choose to keep the equivalent of $12 he was allocated, or to give all or part of it to an anonymous other player.

 

Those involved also provided DNA samples which were analyzed and compared to their reactions. It was found that those who had certain variants of a gene called AVPR1a gave on average nearly 50 percent more money than those not displaying that variant.

 

The gene AVPR1a codes for the production of a receptor that enables a hormone, arginine vasopressin, to act on brain cells. Vasopressin, in turn, has been implicated in social bonding. The researchers found greater altruism in players in which a key section of the AVPR1a gene, called its promoter, was longer. The promoter is the region of a gene that allows cellular machinery to bind to it and determine how much gene product is made. In the case of this gene, a longer promoter can result in greater activity.

 

The findings could help biologists sort out altruism's evolutionary history, according to the scientists. They noted that a version of AVPR1a also exists in rodents called voles, where it also promotes social bonding. This suggests that altruism has a long rooted genetic history, which may have taken on a new role during human evolution.

 

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Dr. Ariel Knafo conducted the research along with other researchers, including Prof. R. P. Ebstein, Prof. Gary Bornstein, and Salomon Israel of the Psychology Department at the The Hebrew University of Jerusalem. 

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Individual differences in allocation of funds in the dictator game associated with length of the arginine vasopressin 1a receptor RS3 promoter region and correlation between RS3 length and hippocampal mRNA. A. Knafo, S. Israel, A. Darvasi, R. Bachner-Melman, F. Uzefovsky, L. Cohen, E. Feldman, E. Lerer, E. Laiba, Y. Raz, L. Nemanov, I. Gritsenko, C. Dina, G. Agam, B. Dean, G. Bornstein, R. P. Ebstein. Genes, Brain and Behavior. doi:10.1111/j.1601-183X.2007.00341.x.

 

Abstract. Human altruism is a widespread phenomenon that puzzled evolutionary biologists since Darwin. Economic games illustrate human altruism by showing that behavior deviates from economic predictions of profit maximization. A game that most plainly shows this altruistic tendency is the Dictator Game. We hypothesized that human altruistic behavior is to some extent hardwired and that a likely candidate that may contribute to individual differences in altruistic behavior is the arginine vasopressin 1a (AVPR1a) receptor that in some mammals such as the vole has a profound impact on affiliative behaviors. In the current investigation, 203 male and female university students played an online version of the Dictator Game, for real money payoffs. All subjects and their parents were genotyped for AVPR1a RS1 and RS3 promoter-region repeat polymorphisms. Parents did not participate in online game playing. As variation in the length of a repetitive element in the vole AVPR1a promoter region is associated with differences in social behavior, we examined the relationship between RS1 and RS3 repeat length (base pairs) and allocation sums. 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). We also implemented a family-based association test, UNPHASED, to confirm and validate the correlation between the AVPR1a RS3 repeat and monetary allocations in the dictator game. Dictator game allocations were significantly associated with the RS3 repeat (global P value: likelihood ratio χ2 = 11.73, df = 4, P = 0.019). The association between the AVPR1a RS3 repeat and altruism was also confirmed using two self-report scales (the Bardi–Schwartz Universalism and Benevolence Value-expressive Behavior scales). RS3 long alleles were associated with higher scores on both measures. Finally, long AVPR1a RS3 repeats were associated with higher AVPR1a human post-mortem hippocampal messenger RNA levels than short RS3 repeats (one-way analysis of variance (ANOVA): F = 15.04, P = 0.001, df = 14) suggesting a functional molecular genetic basis for the observation that participants with the long RS3 repeats allocate more money than participants with the short repeats. This is the first investigation showing that a common human polymorphism, with antecedents in lower mammals, contributes to decision making in an economic game. The finding that the same gene contributing to social bonding in lower animals also appears to operate similarly in human behavior suggests a common evolutionary mechanism.

 

 

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