Friends or foes: Infants use shared evaluations to infer others’ social relationships.

Predicting others' affiliative relationships is critical to social cognition, but there is little evidence of how this ability develops. We examined 9-month-old infants' inferences about 3rd-party affiliation based on shared and opposing evaluations. Infants expected 2 people who expressed shared evaluations to interact positively, whereas they expected 2 people who expressed opposing evaluations to interact negatively. A control condition revealed that infants' expectations could not be due to mere perceptual repetition. Thus, an abstract understanding that 3rd-party affiliation can be based on shared intentions has roots in the 1st year of life. These findings have implications for understanding humans' earliest representations of the social world.