boys in situations of mutual interdependence, an effort which eventually resulted in relative harmony between the two groups. Sherif concluded from this experiment that negative attitudes toward out-groups arise when groups compete for limited resources. However, he also theorized that inter-group frictions could be reduced and positive relations created, but only in the presence of an overarching goal, which could only be achieved with the two groups' cooperation. Self-esteem According to social identity theory, one of the key determinants of group biases is the need to improve self-esteem. The desire to view one's self positively is transferred onto the group, creating a tendency to view one's own group in a positive light, and by comparison, outside groups in a negative light. That is, individuals will find a reason, no matter how insignificant, to prove to themselves why their own group is superior. This phenomenon was pioneered and studied most extensively by Henri Tajfel, a British social psychologist who looked at the psychological root of in-group/out-group bias. To study this in the lab, Tajfel and colleagues created minimal groups (see minimal group paradigm), which occur when "complete strangers are formed into groups using the most trivial criteria imaginable". In Tajfel's studies, participants were split into groups by flipping a coin, and each group then was told to appreciate a certain style of painting none of the participants were familiar with when the experiment began. What Tajfel and his colleagues discovered was that—regardless of the facts that a) participants did not know each other, b) their groups were completely meaningless, and c) none of the participants had any inclination as to which "style" they like better—participants almost always "liked the members of their own group better and they rated the members of their in-group as more likely to have pleasant personalities". By having a more positive impression of individuals in the in-group, individuals are able to boost their own self-esteem as members of that group. Robert Cialdini and his research team looked at the number of university T-shirts being worn on college campuses following either a win or loss at the football game. They found that the Monday after a win, there were more T-shirts being worn, on average, than following a loss. In another set of studies, done in the 1980s by Jennifer Crocker and colleagues using the minimal group paradigm, individuals with high self-esteem who suffered a threat to the