a) Sigmund Freud was an Austrian neurologist who found the discipline of psychoanalysis. His ideas had such a strong impact on psychology that an entire school of thought emerges from his work. While it was eventually replaced by the rise of behaviorism, psychoanalysis had a lasting impact on both psychology and psychotherapy.

b) He developed Seduction theory, in which he posited the solution to the problem of the origins of hysteria and obsessional neurosis. According to the theory, a repressed memory of an early childhood sexual abuse or molestation experience was the essential precondition for hysterical or obsessional symptoms, with the addition of an active sexual experience up to the age of eight for the later.

c) He also developed “psychodynamics” to describe the processes of the mind as flow of psychological energy in an organically complex brain. This theory is based on the premise that human behavior and relationships are shaped by conscious and unconscious influence.