Social intelligence hypothesis

Nick Humphreys, in " The Social Function of Intellect"  (1976) ,  first proposed that the adaptive value of intelligent behaviour in animals lies not just in technical domains such as tool use for extractive foraging (the so-called "ecological intelligence hypothesis"), but through group living a  variety  of different selective pressures would lead to the evolution of more "intelligent" behavior. The social intelligence hypothesis thus encompasses the  Machiavellian intelligence hypothesis  and social brain hypothesis  which can be seen as related theories as to how social living would lead to greater intelligence.

Humphreys posited a variety different consequences of group living, such as: The research program of social intelligence has mostly explored in comparative cognition research, comparing the cogntiive abilities of different animals. Much less work has been done on providing concrete evidence that adaptations for social living (i.e. social learning) are actually adaptive. .
 * Social Learning allows for intelligent behavior to spread without the need for individuals innovating, and can actually "substitute" intelligence in some ways.
 * Exploiting, deciving and out-manoeuvring conspecifics will be adaptive and require being able to understand both the consequences of their own behavior and to calculate the behavior of others, as well as a variety of other complex abilities. The latter ability is now called "theory of mind" and has been studied intesively in the comparative perspective. The Machiavellian intelligence hypothesis specifically refers to the evolution of social intelligence in this domain.
 * Co-operation between conspecifics, what Humphreys termed sympathy, may evolve in conjuction with more selfish forms of behavior as outlined in the machiavellian intelligence hypothesis. Humphreys believed that relationships based on  "mutual give and take", will also be adaptive for individuals.

Social learning and its adaptiveness
Social learning is a widespread skill amongst animals, however it varies in complexity across taxa, although research many speces other than primates is still in its infancy. There are varying views on its adaptive value, however, with the prevailing assumption that it is an adaptive skill being questioned by some.