Ingestive Classics
P. T. Young and the Hedonic Control of Eating


Psychologic factors regulating the feeding process. American Journal of Clinical Nutrition 5: 154-161, 1957.

Comments by Kent Berridge (July 2014)

Paul Thomas Young was a pioneer in the study of hedonic controls of eating, or the role of palatability in ingestive behavior. As he puts it in this classic article, “The hedonic hypothesis states that animals learn to select and to seek foods which they like rather than foods which they need, or require nutritionally” ([1], p. 158). Needs, Young proposed, do not control intake directly but may interact with taste to change what is liked. Further, for a physiological need to be actually expressed in behavior as an alteration in food selection or amount eaten, special circumstances may be required.

Young completed his PhD in 1918 in Titchener’s introspectionist psychology laboratory at Cornell University. His PhD studied human subjects’ ratings of sensory pleasure of mixtures of stimuli, including10 taste stimuli (e.g., sucrose, NaCl, quinine, vinegar, apple, castor oil, etc). In those studies, Young gave combined stimuli (e.g., sour and bitter tastes) to people, and asked them to try to rate simultaneously the mixture of sensory pleasantness and unpleasantness of the mixture. He was tackling an age-old question that continues to be debated in affective psychology today. One side of that debate posits pleasantness-unpleasantness to be essentially a single dimension, and by implication to be mediated potentially by a single affective mechanism in the brain. Empirically, this 1-dimension view predicts that any shift away from positive taste pleasantness will also necessarily be a shift towards hedonic zero and eventually toward negative displeasure. This view began with Wilhelm Wundt. The other side of the debate holds pleasure to be a distinct dimension from displeasure, so that each might have its own distinct mechanism in the brain. This 2-dimension view allows pleasure to change without necessarily altering displeasure; and vice versa. Based on his PhD results, Young supported the 1-dimension side: he found that any increase in rated taste unpleasantness always produced a corresponding opposite decrease in pleasantness of the taste mixture. He concluded that people could simultaneously register the different stimuli, but the hedonics were blended. In my own PhD studies with Harvey Grill on taste reactivity in rats, we reached an opposite 2-dimension conclusion [2,3]. In retrospect, I think the question is still open.

At the time two mechanisms for terminating a meal had been proposed. One was increased glucose utilization in the brain (Mayer, 1953). But if decreased glucose utilization was not the mechanism for the control of initiating and eating meals under usual conditions (Smith et al., 1972), then increased glucose utilization was not a mechanism for the termination of eating.

Young shifted his studies to rats and ingestive behavior in the 1920s, and stayed with that topic for the rest of his career. Much of his work continued to use tastes and sometimes mixtures of tastes. For example, he studied ‘isohedonic curves’, or conditions under which two different tastant solutions would become equally preferred (e.g., a dilute sucrose concentration versus a concentrated sucrose/quinine mixture). Young focused on short-term preference tests between two choices, and on effects induced by physiological hunger states, specific appetites, and nutrient deficiencies in altering taste preference.

In this classic review article of 1957, Young stresses that food selection and intake is never controlled by a single ‘appetite’ factor. Instead, he argues that several different factors always occur together, and interact and compete to control ingestion (and need to be teased apart by experimenters). Palatability is one factor, and is influenced by the individual’s relevant physiological state as well as by the taste itself. Since physiological state can change over time, the palatability of a given taste can also change. This is an early premonition of the concept of alliesthesia, later to be demonstrated so well by Michel Cabanac [4] and others.

However, Young showed that a shifted preference may not be expressed once food selection has become habitual. That is, a learned selection habit can sometimes mask the preference shift induced by a physiological deficit state. But if an entirely new choice situation is arranged, the new, shifted preference is revealed. In an illustrative experiment, he describes rats given the choice between sucrose and a concentrated protein (casein). Ordinarily rats clearly prefer sucrose over casein. Then the rats were put on a protein-deficient diet, to the point they became severely protein deficient (developing gastric lesions, etc.). Remarkably, the rats still preferred sucrose over casein in their familiar choice test (i.e., they failed to show a ‘wisdom of the body’ change to select the food that would correct their deficiency). But equally remarkably, if the protein-deficient rats were instead tested on the same foods in a different and novel Y-maze test, so they had to run to the end of one arm to get sucrose or to the other arm to get casein, they rapidly displayed a preference for casein. As Young describes it “The initial preference of sugar to casein was based upon palatability relations. It is commonly known that rats like sugar and do not like casein (although they will accept it). The first preferential habit (for sugar) was persistent;” but the new Y maze task “required the animals to form a new habit and this new habit developed in agreement with manifest bodily needs” ([1], p. 157; italics original). It is not the preference per se, in other words, but the change in preference revealed in the new situation that best reflects food acceptability, determined by the interaction between food taste and nutritional state

Young surveyed similar effects with thiamine or B1 vitamin deficiency, a phenomenon later shown by Paul Rozin in another classic series of studies [5,6] to be mediated by an acquired taste avoidance that the deficient rat gradually learns to all the familiar thiamin-lacking foods. In another demonstration of how physiological thirst state modulates palatability, Young also showed here how rats ordinarily prefer tap water over distilled water, but that preference becomes obliterated and equalized when tested thirsty. He interpreted that change as showing that thirst massively magnified the palatability of both water tastes, so that any slight pre-existing differences between them were lost in thirst (again, an alliesthesia effect).

P.T. Young worked with very limited tools of his era: manipulating food content, a few physiological states, two-choice preference tests and runway tests. He was constrained by the limitations of those tools, by the lack of nearly any neuroscience, and by the poverty of the psychological concepts available. But he helped keep alive the study of food palatability and hedonic processes during ‘dark decades’ of behaviorism between 1920-1960, when hedonic concepts were shunned by nearly everyone else in both physiology and psychology. Young made thoughtful attempts to study an important topic, and deserves to be remembered by all who study ingestive behavior today.

Acknowledgment: I thank Nori Geary for pointing out this particular article as being available for reproduction, and thank Barry Levin and Nori Geary together for the invitation to contribute to this ‘classics’ series.


[1] Young PT. Psychologic factors regulating the feeding process. Am J Clin Nutr 5: 154-161, 1957.

[2] Berridge KC, Grill HJ. Alternating ingestive and aversive consummatory responses suggest a two-dimensional analysis of palatability in rats. Behav Neurosci 97: 563-573, 1983.

[3] Berridge KC, Grill HJ. Isohedonic tastes support a two-dimensional hypothesis of palatability. Appetite 5: 221-231, 1984.

[4] Cabanac M. Physiological role of pleasure. Science 173: 1103-1107, 1971.

[5] Rozin P. Specific aversions as a component of specific hungers. J Comp Physiol Psychol 64: 237-242, 1967.

[6] Rozin P, Kalat JW. Specific hungers and poison avoidance as adaptive specializations of learning. Psychol Rev 78: 459-486, 1971.