"I know you don't know I know…" children use second-order false-belief reasoning for peer coordination.

Numerous studies have investigated children's abilities to attribute mental states, but few have examined their ability to recruit these abilities in social interactions. Here, 6-year-olds (N = 104) were tested on whether they can use first- and second-order false-belief understanding to coordinate with peers. Children adjusted their decisions in a coordination game in response to either their partner's erroneous belief or their partner's erroneous belief about their own belief-a result that contrasts with previous findings on the use of higher order "theory of mind" (TOM) reasoning at this age. Six-year-olds are thus able to use their higher order TOM capacities for peer coordination, which marks an important achievement in becoming competent social collaborators.