||A model for behavior of agents, connected by a private positive externality, is presented. Maximization of the probability of survival of the receiver of externality is presumed. The survival depends on survival of another agent. For that reason the receiver of externality hands over information to him. It increases his productivity and probability of his survival. The model shows, that creation a handover of information is useful for both subjects and that increasing effect of information can paradoxically lead to increasing donation by information of the receiver of the externality.