This paper addresses a new cooperation technique for multi-agent systems. This technique is based on human social behavior. Multiple robot cooperation has a potential to flexible and adaptable to environment and task variations. In this paper, the personality of each agent is controlled autonomously by interaction among agents. We especially focus on human behavior imitating other persons who work well. We implement an egoistic parameter and an altruistic parameter as personality to the agents. By the combination of these parameters, the personality is decided. Each agent updates these parameters automatically every constant time to improve performance of the whole system.