The belief that the unconscious mind has an influence on one's behavior is part of what early field of psychology? structuralism functionalism psychoanalysis behaviorism

I believe the answer is: psychoanalysis

Psychoanalysis refers to a technique to study a certain psychological problem by analyzing the unconscious mind. This type of analysis usually would be carried out by making the subject take an abstract psychological test (such as rorschach test) and having an expert in psychology to interpret the result of the test.