Final answer:
Sigmund Freud developed the Psychosexual Theory of Development, which includes five stages centered on different erogenous zones. These stages influence personality and behavior, and challenges during them can lead to adult fixation. The theory is controversial but has been significant in psychoanalytical psychology.
Step-by-step explanation:
The Psychosexual Theory of Development was developed by Sigmund Freud, an influential psychoanalyst. According to Freud, during early childhood, our personalities and behaviors as adults are shaped. His theory delineates five stages in which pleasure-seeking urges, associated with the id, are centered on different erogenous zones of the body.
Freud believed that unconscious sexual and aggressive urges were key to understanding neuroses and personality development. However, his method of using recollections and dream interpretations as proof has been criticized, and later psychologists like Erik Erikson would build on his work while adding more emphasis on the social aspects of personality development.