Ori Weisel

Oxytocin, but not vasopressin, increases both parochial and universal altruism

In todays increasingly interconnected world, deciding with whom and at what level to cooperate becomes a matter of increasing importance as societies become more globalized and large-scale cooperation becomes a viable means of addressing global issues. This tension can play out via competition between local (e.g. within a group) and global (e.g., between groups) interests. Despite research highlighting factors influencing cooperation in such multi-layered situations, their biological basis is not well understood. In a double-blind placebo controlled study, we investigated the influence of intranasally administered oxytocin and arginine vasopressin on cooperative behavior at local and global levels. We find that oxytocin causes an increase in both the willingness to cooperate and the expectation that others will cooperate at both levels. In contrast, participants receiving vasopressin did not differ from those receiving placebo in their cooperative behavior. Our results highlight the selective role of oxytocin in intergroup cooperative behavior.

Punishment, cooperation, and cheater detection in 'noisy' social exchange

Explaining human cooperation in large groups of non-kin is a major challenge to both rational choice theory and the theory of evolution. Recent research suggests that group cooperation can be explained by positing that cooperators can punish non-cooperators or cheaters. The experimental evidence comes from public goods games in which group members are fully informed about the behavior of all others and cheating occurs in full view. We demonstrate that under more realistic information conditions, where cheating is less obvious, punishment is much less effective in enforcing cooperation. Evidently, the explanatory power of punishment is constrained by the visibility of cheating.

A Flexible z-Tree Implementation of the Social Value Orientation Slider Measure (Murphy et al. 2011) – Manual

This manual describes a z-Tree (Fischbacher, 2007) implementation of the paper-based Social Vaule Orientation (SVO) Slider Measure by Murphy et al. (2011). Using the paper-based version instead of the slider-based version (as implemented on the SVO-Website) avoids server-traffic related delays we experienced in the latter implementation.

Negative and positive externalities in intergroup conflict: exposure to the opportunity to help the outgroup reduces the inclination to harm it

Outgroup hate, in the context of intergroup conflict, can be expressed by harming the outgroup, but also by denying it help. Previous work established that this distinction—whether the externality on the outgroup is negative or positive—has an important effect on the likelihood of outgroup hate emerging as a motivation for individual participation in intergroup conflict. The current work uses a within-subject design to examine the behavior of the same individuals in intergroup conflict with negative and positive externalities on the outgroup. Each participant made two choices, one for each type of externality, and the order was counter balanced. The main results are that (1) behavior is fairly consistent across negative and positive externalities, i.e., the tendency to display outgroup hate by harming the outgroup is correlated with the tendency to display outgroup hate by avoiding to help the outgroup; (2) People are reluctant to harm the outgroup after being exposed to the opportunity to help it; (3) Groupness—the degree to which people care about their group and its well-being—is related to outgroup hate only when participants encounter the opportunity to harm the outgroup first (before they encounter the opportunity to help it). In this setting the relationship between groupness and outgroup hate spilled over to the subsequent interaction, where it was possible to help the outgroup. When the opportunity to help the outgroup was encountered first, groupness was not related to outgroup hate.