The oxytocin receptor (OXTR) contributes to prosocial fund allocations in the dictator game and the social value orientations task

Abstract

Background: Economic games observe social decision making in the laboratory that involves real money payoffs. Previously we have shown that allocation of funds in the Dictator Game (DG), a paradigm that illustrates costly altruistic behavior, is partially determined by promoter-region repeat region variants in the arginine vasopressin 1a receptor gene (AVPR1a). In the current investigation, the gene encoding the related oxytocin receptor (OXTR) was tested for association with the DG and a related paradigm, the Social Values Orientation (SVO) task.

Methodology/principal findings: Association (101 male and 102 female students) using a robust-family based test between 15 single tagging SNPs (htSNPs) across the OXTR was demonstrated with both the DG and SVO. Three htSNPs across the gene region showed significant association with both of the two games. The most significant association was observed with rs1042778 (p = 0.001). Haplotype analysis also showed significant associations for both DG and SVO. Following permutation test adjustment, significance was observed for 2-5 locus haplotypes (p<0.05). A second sample of 98 female subjects was subsequently and independently recruited to play the dictator game and was genotyped for the three significant SNPs found in the first sample. The rs1042778 SNP was shown to be significant for the second sample as well (p = 0.004, Fisher's exact test).

Conclusions: The demonstration that genetic polymorphisms for the OXTR are associated with human prosocial decision making converges with a large body of animal research showing that oxytocin is an important social hormone across vertebrates including Homo sapiens. Individual differences in prosocial behavior have been shown by twin studies to have a substantial genetic basis and the current investigation demonstrates that common variants in the oxytocin receptor gene, an important element of mammalian social circuitry, underlie such individual differences.

Figure 1. Distribution of Dictator allocations for student and mother samples.

Allocation sums by participants grouped in 5 increments ( 5≈$1.17). For both samples, the modal value of 25 was used as the cutoff point to divide participants into low and high allocators.

Figure 2. Cross tabulation of Dictator and SVO allocation of funds.

Cross tabulation of Dictator giving with Social Value Orientation (SVO). High givers in the DG were significantly more likely to maintain prosocial value orientations as compared to low givers.

Figure 3. Visual schematic of the oxytocin receptor.

Schematic representation of chromosome 3 and the oxytocin receptor (OXTR) gene with the location of the 16 tagging single-nucleotide polymorphisms (SNPs).

Figure 4. Comparison of SVO Prosocial Responses by OXTR SNPs.

Average number of prosocial responses in the Social Value Orientation task categorized by the three most significant OXTR SNPs. A family-based analysis for the three SNPs showed significant association with prosocial value orientations (PBAT dominant model: rs1042778 p = 0.001, rs2268490 p = 0.011, and rs237887 p = 0.005).

Figure 5. Association between OXTR haplotypes and allocation of funds in the Dictator Game (high versus low allocators) and Social Value Orientations. Haplotypes are indicated in outlined blocks.

¹ UNPHASED global p-value, additive model ² UNPHASED permutation test for the haplotype block ³ PBAT multi-variate statistic, dominant model.