The note is restricted to three types of group models: 1) conflict model; 2) structural and functional model; and 3) cybernetic-growth model. The conflict model assumes that no group has sufficient resources to fulfil either all internal needs or all external demands. As some members of the group are more competent, conflict is unavoidable. The structural-functional model assumes that the group will stay intact and grow if the members share the view that it is progressing towards its goal. The model is biased and favours status quo. The cybernetic-growth model assumes the presence of group agents who observe and assess the situation, and act to preserve and promote the group's survival and growth. But the model does not explain human drives or the directions such drives tend to take.