I believe psychologists study human behavior, thought processes, and how these two are linked. Psychologists study the human brain and how the brain works. They study human behavior and conduct experiments to answer a hypothesis or research question being asked on human behavior. Sometimes the experiment turns out to be correct with the hypothesis being tested and sometimes it's not depending on the outcome of the experiment and how the participants reacted to the experiment. Psychologists also study the mental processes of a person's brain and answers the question why people behave the way they do.