This document summarizes theories of infant psychosocial development in the first two years. It discusses emotional development in infancy, including specific emotions like pleasure, pain, social smiles, anger, fear, and separation anxiety. It also covers theories from Freud, Erikson, behaviorism, cognitive theory, and sociocultural theory. Attachment styles like secure, avoidant, resistant, and disorganized are defined. The development of social bonds through synchrony, attachment, and social referencing are also summarized.