This paper presents a general theory of child development that incorporates interactive learning and identity formation in social interactions with caregivers. The model sheds light on many puzzling aspects of child development. Child learning responds nonmonotonically to caregivers' attention and approval in social interactions. I highlight key parental characteristics associated with child learning, and identity formation. The theory also explains why media devices widen human inequality. Lessons are finally drawn for the design of policies that alleviate human inequality.