“motivation: Factors within a human being or animal that arouse and direct goal-oriented behavior. Motivation has long been a central subject of study in psychology. Early researchers, influenced by Charles Darwin, ascribed much of animal and human behavior to instinct. Sigmund Freud believed that much of human behavior was also based on irrational instinctive urges or unconscious motives. Walter Cannon proposed that basic human drives served homeostatic functions by directing energies toward the reduction of physiological tensions. Behavioral psychologists, in contrast, stress the importance of external goals in prompting action, while humanistic psychologists examine the role of felt needs. Cognitive psychologists have found that a motive sensitizes a person to information relating to that motive: a hungry subject, for example, will perceive food stimuli as larger than other stimuli. See also behavior genetics, human nature, learning.”
Excerpted from: Stevens, Mark A., Ed. Merriam-Webster’s Collegiate Encyclopedia. Springfield, Massachusetts: Merriam-Webster, 2000.