Social motivation predicts gaze following between 6 and 14 months.

Infants vary in their ability to follow others' gazes, but it is unclear how these individual differences emerge. We tested whether social motivation levels in early infancy predict later gaze following skills. We longitudinally tracked infants' (N = 82) gazes and pupil dilation while they observed videos of a woman looking into the camera simulating eye contact (i.e., mutual gaze) and then gazing toward one of two objects, at 2, 4, 6, 8, and 14 months of age. To improve measurement validity, we used confirmatory factor analysis to combine multiple observed measures to index the underlying constructs of social motivation and gaze following. Infants' social motivation-indexed by their speed of social orienting, duration of mutual gaze, and degree of pupil dilation during mutual gaze-was developmentally stable and positively predicted the development of gaze following-indexed by their proportion of time looking to the target object, first object look difference scores, and first face-to-object saccade difference scores-from 6 to 14 months of age. These findings suggest that infants' social motivation likely plays a role in the development of gaze following and highlight the use of a multi-measure approach to improve measurement sensitivity and validity in infancy research.