Psychologists generally consider biology the substrate of thought and feeling, and therefore an important area of study. Behaviorial neuroscience, also known as biological psychology, involves the application of biological principles to the study of physiological and genetic mechanisms underlying behavior in humans and other animals. The allied field of comparative psychology is the scientific study of the behavior and mental processes of non-human animals. A leading question in behavioral neuroscience has been whether and how mental functions are localized in the brain. From Phineas Gage to H.M. and Clive Wearing, individual people with mental deficits traceable to physical brain damage have inspired new discoveries in this area. Modern behavioral neuroscience could be said to originate in the 1870s, when in France Paul Broca traced production of speech to the left frontal gyrus, thereby also demonstrating hemispheric lateralization of brain function. Soon after, Carl Wernicke identified a related area necessary for the understanding of speech.
The contemporary field of behavioral neuroscience focuses on the physical basis of behavior. Behaviorial neuroscientists use animal models, often relying on rats, to study the neural, genetic, and cellular mechanisms that underlie behaviors involved in learning, memory, and fear responses. Cognitive neuroscientists, by using neural imaging tools, investigate the neural correlates of psychological processes in humans. Neuropsychologists conduct psychological assessments to determine how an individual’s behavior and cognition are related to the brain. The biopsychosocial model is a cross-disciplinary, holistic model that concerns the ways in which interrelationships of biological, psychological, and socio-environmental factors affect health and behavior.
Evolutionary psychology approaches thought and behavior from a modern evolutionary perspective. This perspective suggests that psychological adaptations evolved to solve recurrent problems in human ancestral environments. Evolutionary psychologists attempt to find out how human psychological traits are evolved adaptations, the results of natural selection or sexual selection over the course of human evolution.
The history of the biological foundations of psychology includes evidence of racism. The idea of white supremacy and indeed the modern concept of race itself arose during the process of world conquest by Europeans. Carl von Linnaeus‘s four-fold classification of humans classifies Europeans as intelligent and severe, Americans as contented and free, Asians as ritualistic, and Africans as lazy and capricious. Race was also used to justify the construction of socially specific mental disorders such as drapetomania and dysaesthesia aethiopica—the behavior of uncooperative African slaves. After the creation of experimental psychology, “ethnical psychology” emerged as a subdiscipline, based on the assumption that studying primitive races would provide an important link between animal behavior and the psychology of more evolved humans.