Final answer:
Wilhelm Wundt is the theorist who used structuralism to study human behavior, focusing on the components of consciousness.
Step-by-step explanation:
The theorist who used the structuralism approach to studying human behavior is Wilhelm Wundt. Structuralism is a framework that posits that the human mind and its perceptions can be broken down into elementary components. Wilhelm Wundt, often regarded as the father of psychology, established the first psychology laboratory and utilized introspection to explore the constituents of consciousness, which is the essence of structuralism. He aimed to identify the smallest elements of the mind in much the same way that a chemist breaks down chemicals into their purest elements. This contrasts with the approaches of Sigmund Freud, who developed psychoanalysis, Abraham Maslow, who was a humanistic psychologist, and John B. Watson, who was a behaviorist and heavily focused on observable behavior rather than internal mental processes.