Aggression is the mark of unsettled dominance order. Productive group cooperation requires that both dominance order and territorial arrangements (identity, self-concept) be settled with respect to the common goal and within the particular group. Some individuals may withdraw from interaction or be excluded from the developing group. Depending on the number of individuals in the original collection of strangers, and the number of "hangers-on" that are tolerated, one or more competing groups of ten or less may form, and the competition for territory and dominance will then also be manifested in the inter group transactions.