Physiological psychology explains behavior from a biological point of view. According to a physiological psychologist, only the accepted facts and theories of biology can help to understand human behavior. The purpose is to reveal the relationship between behavior and the underlying physiological mechanisms.
Some of the investigations that a physiological psychologist does include exploring the relationship of biochemistry to memory, studying the activities in individual nerve cells, reactions of blood vessels and sweat glands in the skin and their relation to changes in emotion, etc. Some approaches to study physiological psychology include: a comparative approach, developmental approach, and clinical approach.
In a comparative approach, experiments on animals are conducted, known damages are produced, and the effects are compared with the results of damage to other regions. A comparison is made between several species of animals. In the developmental approach, problems are approached from a developmental point of view. In the clinical approach, clinical psychologists who investigate patients with brain damage use methods drawn from classical neurobiology and neurosurgery, experimental psychology as well as physiological psychology.