Theories provide explanations for sexual phenomena. Sociobiologists view human sexual behaviors as the product of natural selection in evolution and thus view these behavioral patterns as being genetically controlled. Contemporary evolutionary theorists view behavior as the result of an interaction between evolved mechanisms and environmental influence.

Among the psychological theories, Freud's psychoanalytic theory views the sex energy, or libido, as a major influence on personality and behavior. Freud introduced the concepts of erogenous zones and psychosexual stages of development. Learning theory emphasizes how sexual behavior is learned and modified through reinforcements and punishments according to principles of operant conditioning. Behavior modification techniques-therapies based on learning theory-are used in treating sexual variations and sexual disorders. Social learning theory adds the concepts of imitation, identification, and self-efficacy to learning theory. Exchange theory highlights the role of rewards and costs in relationships. Cognitive psychologists focus on people's thoughts and perceptions-whether positive or negative-and how these influence sexuality.

Sociologists study the ways in which society influences our sexual expression. At the macro level of analysis, sociologists investigate the ways in which institutions such as religion, the economy, the family, medicine, and the law influence sexuality. Symbolic interaction theory calls attention to processes of communication and interaction. Sexual scripts provide us with guidelines for behavior in many situations. Reiss argues that all societies regard sexuality as important because it is associated with great physical pleasure and self-disclosure.