Johnson and Johnson argue that Co-operative Learning works because it encourages social interdependence and facilitates relationships:
Caring and committed friendships come from a sense of mutual accomplishment, mutual pride in joint work, and the bonding that results from joint efforts.
The more students care about each other, the harder they will work to achieve mutual learning goals. Long-term and persistent efforts to achieve do not come from the head; they come from the heart. Individuals seek out opportunities to work with those they care about. As caring increases, so do feelings of personal responsibility to do one's share of the work, a willingness to take on difficult tasks, motivation and persistence in working toward goal achievement, and a willingness to endure pain and frustration on behalf of the group. All these contribute to group productivity.
In addition, the joint success experienced in working together to get the job done enhances social competencies, self-esteem, and general psychological health.