Fifth, at the other end of the spectrum is the need for psychobiologists to include more data from human experience in our inquiry. In the attempt to be scientific in the past, we may have confused behaviorism with materialism and the avoidance of philosophical dualism. To the psychobiologist, subjective human experience comes from the physical brain, and is as much a function to be measured as overt behavior. The measurement may be difficult, but that does not mean that the function of reportable experience should be ruled out. Therefore, we have included human subjective reports, given on an analogue rating scale or in a magnitude estimation, along with accompanying behavioral data on the same subjects. Taken together with animal data, the human data add a new dimension to the inquiry.
Sixth, in one area, that of brain-stimulation reward, we may be close to identifying the brain substrate in a way that has never been done for a behavioral phenomenon as "psychological" as reward. We have two major clues: a rapidly growing, fine-grained psychophysical characterization of the behaviorally relevant axons that are directly excited by an electrode in the lateral hypothalamus (Gallistel, Shizgal, & Yeomans, 1981), and a strong implication of dopamine as an important neurotransmitter (Wise, 1982). What makes the field even more exciting is the possibility of forming a link between these two clues. That is, the behaviorally relevant axonal characterization suggests a connection between the axons excited by the electrode and the brain area containing dopamine cells.
Finally, we see the study of motivation and reward as moving in two directions. One direction is yielding a better and more powerful biological reductionism, which is coming about because of the development of powerful cellular and neurochemical techniques. Such techniques let us trace anatomic pathways in great detail and specify neurotransmitters and peptide neuromodulators, their agonists and antagonists, and their specific cellular receptor sites and channels. The other direction is our greater ability to use concepts and principles to synthesize and see function as a whole. The principles of hierarchical organization and peri pheraVcentral- neural interaction are fundamental insights. Perhaps broader and of even greater impact is the recognition that motivated behavior is generated by the neurobiological mechanisms responsible for homeostasis and physiological regulation on the one hand, yielding reward and reinforcement/and producing affect and human hedonic experience on the other. (Stellar and Stellar 1985, 4–5)
References
Stellar, James R., and Eliot Stellar. 1985. The neurobiology of motivation and reward. New York: Springer-Verlag.