Final answer:
The theory that minimized the role of the unconscious is the D) Behaviorist theory. Behaviorism differs significantly from the Psychoanalytic perspective by focusing on observable behaviors over internal mental states like the unconscious.
Step-by-step explanation:
The theory that minimized the role of the unconscious is the Behaviorist theory. Unlike Sigmund Freud's Psychoanalytic theory, which emphasizes the unconscious mind's significant influence on behavior, Behaviorist theory focuses on observable and measurable behaviors, largely discounting internal mental states like the unconscious.
Freud's Psychoanalytic perspective viewed the unconscious as a repository of feelings, thoughts, urges, and memories outside of conscious awareness, strongly affecting our behavior. On the contrary, Behaviorism posits that behavior is the result of environmental stimuli and responses, without the need to consider the unconscious.
Therefore, the correct completion for the given statement is: The theory that minimized the role of the unconscious is (D) Behaviorist. Sigmund Freud's research approach, which led to the development of his theory, is best described as a case study, as he conducted in-depth interviews with a few clients over an extended period.