similar effects in Israel ( Hertz-Lazarowitz, Sapir, & Sharan, 1982; Sharan & Shachar, 1988).
A variety of factors appear to be operating together to produce these favorable results. Working in cooperative groups tends to undercut ingroup-outgroup bias. Ingroup-outgroup bias is based on identification with the ingroup and rejection of outgroups. When students work together in mixed teams, they come to identify with and favorably evaluate their own team, which contains members of both the ingroup and the outgroup ( Gaertner, Mann, Dovidio, Murrell, & Pomare, 1989; Gaertner, Mann, Murrell, & Dovidio, 1989). The teams thus become superordinate groups in which initial distinctions between ethnic groups are submerged.
Interaction with outgroup members in cooperative groups also provides the students with an opportunity to acquire information that is inconsistent with their stereotypes. This stereotype-disconfirming information can change stereotypes because it occurs frequently, for a variety of outgroup members, and across a variety of situations (cf. Rothbart & John, 1985). The students also learn that outgroup members vary considerably, which can lead to differentiated perceptions of the outgroup. In addition, in this context the students are dependent on one another and dependence leads to an increased focus on individuating information ( Erber & Fiske, 1984). After reviewing more than 600 studies on cooperative learning groups, one set of researchers concluded that interdependence is the key to the positive effects of cooperative learning ( Johnson & Johnson, 1992a). The Johnsons suggest that mutual interdependence leads people in cooperative groups to put aside their own immediate interests in favor of striving to help all members of the group achieve their joint goals. People take pride in the accomplishments of others and become bound to them by ties of mutual obligation and responsibility leading to feelings of cohesion and attraction to other group members.
One problem that often remains in cooperative classroom groups is that the White students are higher in social class and achievement than the minority students. Cohen ( 1980) and her coworkers have found, however, that even these status inequalities can be overcome if the minority students are highly competent on the assigned tasks. In her studies Cohen trained the minority group members to explicitly disconfirm negative stereotypes concerning minority competence. Another solution to the status inequality problem was originally developed by DeVries and Edwards ( 1974). In their cooperative groups, each student's performance contributes to the team's overall standing. To avoid the possibility that low-achieving students will hinder the