Abstract: The effect of social value orientation on cooperative behavior in social dilemmas has been widely examined in social psychology research. However, only a small to medium effect size has been found. According to the appropriateness model (Weber, Kopelman, & Messick, 2004), decision making in social dilemmas can be shaped by one’s identity, situational recognition, and the application of rules. Thus, individual characteristics interacting with situational factors affect decision making in social dilemmas. Therefore, the unequal resources with which individuals are endowed in asymmetric social dilemmas set up differences in endowment dominance and serve as contextual cues that may shape cooperative behavior differently for prosocials and proselfs. This study hypothesized that prosocials would be sensitive to difference in endowment dominance whereas proselfs would be immune to the difference (H1) and that, compared to proselfs, prosocials would exhibit a higher level of cooperation when they were endowed with less or when their endowments were worth less (H2).
The current study examined the above hypotheses via two experiments. In Experiment 1, participants were randomly assigned to an advantaged condition or a disadvantaged condition. Their social value orientation was measured with a nine-item decomposed game instrument. 90 participants interacted in a fictional two-person prisoner’s dilemma situation. The main results showed that 1) prosocials allocated more tokens to their partner when their endowments were worth less than when their endowments were worth more; and 2) prosocials allocated more to their partner than did proselfs when their endowments were worth less.
Experiment 2 was conducted in a fictional 4-person public good dilemma situation. 191 participants were randomly assigned to an equal condition, an advantaged condition or a disadvantaged condition. Again, their social value orientations were also measured. The main results showed that 1) the amount of their endowments that prosocials contributed in the disadvantaged condition was significantly higher than the average amount of endowments that they contributed in the equal condition and in the advantaged condition; and 2) prosocials contributed more to the group account than did proselfs only when they were endowed with less. This was not the case in either the equal condition or the advantaged condition.
The results from both experiments supported our hypotheses and indicated that the effect of social value orientation on cooperation was moderated by dominance differences stemming from the initial resources that individuals were endowed. The results enrich our understanding on how prosocials and proselfs differ in their response to different distributions of initial resources. It also suggests that such social value orientation effects are still open for exploration. Future research should further explore how prosocials and proselfs behave differently when they face social dilemmas with different situational characteristics.

Key words: social dilemmas, social value orientation, cooperation