Final answer:
A child's cognitive understanding of sex differences is referred to as his or her gender schema, which involves internalizing societal expectations associated with gender roles.
Step-by-step explanation:
A child's cognitive understanding of sex differences would be his or her gender schema. This concept falls under the study of cognitive development and socialization. Gender schema is a theory that refers to the way children learn about the cultural construction of gender roles and develop an internalized understanding of these roles. Through observations and social interactions, children pick up on the societal expectations associated with being male or female and incorporate this information into their own gender identity. In contrast, Electra complex and Oedipal complex are concepts from Freudian psychoanalytic theory that deal with psychological conflicts during the phallic stage of development. The superego represents the moral component of personality in Freud's theory and is not directly related to a child's understanding of sex differences.