Final answer:
Psychoanalysis, developed by Sigmund Freud, examined mental processes in the unconscious mind to explain behavior.
Step-by-step explanation:
The school of thought that examined mental processes in the unconscious mind to explain behavior is Psychoanalysis. Sigmund Freud, an Austrian neurologist, developed this theory and method to understand the hidden elements of the mind that influence behavior. Freud believed that the unconscious mind played a crucial role in shaping conscious behavior, and he used techniques like dream analysis and free association to access this unconscious realm.