“Like chess, a social interaction is typically a transaction between social partners. One animal may, for instance, wish by his own behaviour to change the behaviour of another; but since the second animal is himself reactive and intelligent the interaction soon becomes a two-way argument where each ‘player’ must be ready to change his tactics — and maybe his goals – as the game proceeds. Thus, over and above the cognitive skills which are required merely to perceive the current state of play (and they may be considerable), the social gamesman, like the chess player, must be capable of a special sort of forward planning. Given that each move in the game may call forth several alternative responses from the other player this forward planning will take the form of a decision tree, having its root in the current situation and growing branches corresponding to the moves considered in looking ahead at different possibilities. It asks for a level of intelligence which is, I submit, unparalleled in any other sphere of living. There may be, of course, strong and weak players – yet, as master or novice, we and most other members of complex primate societies have been in this game since we were babies.”
Nicholas K. Humphrey. The social function of intellect. In P. P. G. Bateson and R. A. Hinde, editors, Growing Points in Ethology, pages 303–317. Cambridge University Press, 1976.