Behavioral psychology, or behaviorism, is a theory suggesting that environment shapes human behavior. In a most basic sense, behavioral psychology is the study and analysis of observable behavior. This field of psychology influenced thought heavily throughout the middle of the 20th century. It is still used by mental health professionals today, as its concepts and theories remain relevant in fields like psychotherapy and education. Behavioral psychologists perform the following duties: Conduct research utilizing conditioning and stimuli to study human behavior. Work in social work or counseling to help people understand and change negative behavior, such as drug addiction; or help people suffering from mental health disorders.