Biopsychology represents the approach to psychology that studies the biological events that shape actions, thoughts and feelings. The research conducted by biopsychologists investigates the neural, genetic and endocrine processes that affect behavior. Physiological processes associated with organs other than the brain, such as the stomach and various glands, are also studied to determine their effect on behavioral responses and emotional disorders.
The beginnings of biopsychology, also known as behavioral neuroscience or biological psychology, can be traced as far back as the 17th century when Rene Descartes suggested that physiological factors, such as the pineal gland and the movements of bodily fluid, played a role in human behavior. Descartes was incorrect in the specifics of his assumptions regarding the connections between mind and body, but he and other similarly minded philosophers helped give birth to the emerging science of psychology.
William James, who was trained as a physiologist, wrote what is considered to be one of the earliest textbooks in psychology. In his 1890 book, "The Principles of Psychology," he argued that the new field must be grounded in a study of biology, and that "a certain amount of brain-physiology" must be included in the study of the mind.
In their search to find correlations between physiological events and behavior, biopsychologists look to bodily indicators such as lesions in neural tissue, pharmacological interference in neurotransmissions and, in experiments involving laboratory animals, the results of genetic engineering. As technical sophistication progresses and more non-invasive experimental procedures are developed for human subjects, the biological approach to psychology is contributing to a much greater degree in the areas of consciousness, linguistics, reasoning and decision-making.