Do the insights into human behavior generated by laboratory experiments hold outside the lab? This is a crucial question that naturally troubles both experimentalists and their critics. We address this question by adopting Popper's injunction that hypotheses should be tested, not by seeking...

Do the insights into human behavior generated by laboratory experiments hold outside the lab? This is the crucial question of external validity that naturally troubles both experimentalists and their critics. We address this question by adopting Popper's injunction that hypotheses should be...

In-group favouritism, the practice of treating fellow members of a group better than outsiders is commonplace in social life. It has been observed in the field and the laboratory. Treating people differently in this way is not only a source of tension between groups, when conflict occurs between...