Biological psychology deals mainly with the relationship between the psychological processes and the underlying physiological events; in other words, with the mind-body phenomenon. The focus of its attention is the functioning of the brain and of the other parts of the nervous system, considered in different activities (thinking, learning, feeling, perceiving). Biological psychology is involved in the study of the physical basis of the reception of internal and external stimuli by the nervous system, as regards particularly the visual and auditory system. Other areas of study include the physiological bases of motivated behavior, emotions, learning, memory, cognition and mental disorders. Physical factors that directly affect the nervous system are also considered, including heredity, metabolism, hormones, diseases, drugs and diet.