Teamwork, pleasure and bargaining in animal social behaviour

Intimate behaviour between animals is hypothesized to enable teamwork. The pleasure experienced in grooming, preening, dancing, mating and singing in synchrony is hypothesized to motivate participants to coordinate actions directed towards a shared goal that enhances each individual's fitness. This cooperative behaviour evolves as a mutual direct benefit, not as altruism. Teamwork leads to an equilibrium set of returns to the participants that may be modelled as a Nash bargaining solution instead of as the more familiar Nash equilibrium. The dynamics leading to that equilibrium may be modelled based on joint action instead of the more familiar individualistic action. Confusions by Binmore (J. Evol. Biol. 2010; 23: 1351) about this hypothesis are corrected.