Cooperation involves individuals or groups working together for the achievement of their individual or collective goals. In its simplest form, cooperation may involve only two people who work together towards a common goal. Two college students working together to complete a laboratory experiment, or two inter-city youths working together to protect their 'turf' from violation by outsiders are examples. In these cases, solidarity between the collaborators is encouraged and they share jointly the reward of their cooperation. Again at the level of two-person interactions, the goals towards which the cooperation parties work may be consistent with each other, but they may not be identical or shared. From the college experience again, student and professor may cooperate towards the student's mastery of professor's discipline, but the student may be working to make a good grade while the professor is working to establish or reinforce his/her reputation as a good teacher. If some of their rewards are shared, some also are individual but