This study replicates Andreoni's (Journal of Public Economics, 1988, 37, 291-304) public goods experiments. The results are not consistent with simple learning, but are compatible with strategies, unlike Andreoni's original experiment. An investigation of the variance of contributions provides an organizing explanation of previous results.

Many people incur costs to reward strangers who have been kind to others. Theoretical and experimental evidence suggests that such "indirect rewarding" sustains cooperation between unrelated humans. Its emergence is surprising, because rewarders incur costs but receive no immediate benefits. It can prevail in the long run only if rewarders earn higher payoffs than "defectors" who ignore strange...

We compare a partners condition where the same small group of subjects plays a repeated public good game to a strangers condition where subjects play this game in changing group formations. Subjects in the partners condition contribute from the first period on significantly more to the public good than subjects in the strangers condition. In the strangers condition, contributions show a continu...

In a series of studies, we investigated the role of economic structures (farming vs. herding) and source of ostracism (close other vs. stranger) in social exclusion experiences. We first confirmed that herders rely on strangers to a greater extent than do farmers for economic success (validation study). Next, we verified that farmers and herders understand the concept of ostracism, and its emot...

Who is the best judge of a person’s abilities—the person, knowledgeable informant, or strangers just met in 3-min speed date? To test this, we collected ability measures as well self-, informant- and stranger-estimates verbal, numerical spatial intelligence, creativity, intra- interpersonal emotional competence from 175 young adults. While people themselves were most accurate about majority the...

Cooperatively-breeding and socially-monogamous primates, like marmosets and humans, exhibit high levels of social tolerance and prosociality toward others. Oxytocin (OXT) generally facilitates prosocial behavior, but there is growing recognition that OXT modulation of prosocial behavior is shaped by the context of social interactions and by other motivational states such as arousal or anxiety. ...