This talk tracks the developmental origins of the adult propensity to evaluate others based on their social behaviors. It will examine findings suggesting that even in the first few months of life, preverbal infants distinguish those who engage in third-party prosocial versus third-party antisocial interactions, and prefer prosocial to antisocial others in a variety of social scenarios. It will then examine the consequences of these judgments for intuitions about reward and punishment and for social learning.