Final answer:
Sigmund Freud proposed the psychosexual theory of development, focusing on how personality and sexual development are intertwined through various stages of early childhood.
Step-by-step explanation:
The psychosexual theory of development was proposed by Sigmund Freud, who was an influential psychoanalyst. Freud believed that personality develops during early childhood through a series of stages centered around erogenous zones.
These stages include the oral, phallic, latency, and genital stages. Freud suggested that our childhood experiences shape our adult personalities and behaviors, and that any fixation at a particular stage can affect an individual's personality.
His theory emphasized the connection between personality development and sexual maturation, despite the controversy and skepticism surrounding his methods and conclusions.