A psychologist is trained to study human behavior and the human mind.  Those who work as research psychologists investigate the cognitive, physical, social, and emotional aspects of human behavior.  Those working in applied settings, such as for the government, in industry or business, or for nonprofit organizations are responsible for conducting research, providing training, designing systems, and being an advocate for psychology.  Those within the health services field provide mental care in clinics, hospitals, private settings, and schools.

In order to do their jobs, psychologists must develop hypotheses and collect data in order to test their hypotheses.  The type of research methods utilized vary according to what is being studied.  For example, a psychologist may gather information through a controlled laboratory experiment.   Or, the psychologist might administer performance, personality, intelligence, or aptitude tests.  Other methods for collecting data include interviews, observation, clinical studies, questionnaires, and surveys.  A psychologist may choose to specialize in one particular area.