Step 1: Understanding the Concept:
The question asks for the name of the school of psychology defined by its exclusive focus on observable behavior.
Step 2: Detailed Explanation:
(A) Behaviorism: This is the precise definition of behaviorism, as established by John B. Watson. Behaviorists believe that psychology can only be studied scientifically if it limits its scope to what can be seen and measured: overt behavior and the environmental stimuli that cause it.
(B) Psychoanalysis: This approach, founded by Sigmund Freud, focuses on the influence of the unconscious mind, hidden conflicts, and early childhood experiences on behavior, which are not directly observable.
(C) Gestalt Psychology: This school of thought emphasizes that the whole of experience is greater than the sum of its parts ("The whole is other than the sum of the parts"). It focuses on perception and consciousness, not just overt behavior.
(D) Functionalism: This early school focused on how mental processes help an organism to adapt to its environment. It studied consciousness but was less restrictive than behaviorism.
Step 3: Final Answer:
The science of behavior that focuses only on observable behavior is called Behaviorism.