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Salivation and Appetite: Commentary on the Forum
Appetite: lournalfor Intake Research 1981,2,386-389
Salivation and Appetite: Commentary on the Forum B. J. SAHAKIAN M. R. C. Dunn Clinical Nutrition Centre, Cambridge, U.K.
The purpose of this forum was to assess experimenters' varied experiences of the salivation response to food-related stimuli and the usefulness of salivation as a measure of appetite. Table 1 collates a number of aspects ofthe findings presented by participants in the forum. Earlier data have been summarized in the Wooleys' keynote review. Several interesting questions remain to be answered. Is
THERE AN IDEAL SALIVATION TEST PROCEDURE?
From the majority of the contributions (Table 1), it might be concluded that saliva should be collected on one or perhaps two dental rolls over as little as 1 or perhaps 2 min. However, other methods, such as the collection of saliva in cups (Sahakia.n, Lean, Robbins, & James, 1981) may prove equally successful and less obtrusive. There is reason to suggest that frequent or numerous tests disrupt salivation. On the other hand, the contributions in this forum by Brummer and Pudel, and by Durrant suggest that a single, simply administered procedure cannot always be relied on to give a consistent salivation response in all individuals and indeed, certain individuals may fail to show a response. Other variations in procedure have been discussed-such as whether the food is physically present or only symbolically represented, whether the food presentation allows the subject both to see and smell the food, whether or not the subject is on a diet, whether or not the subject is instructed to consume the food following saliva collection, and the experimental atmosphere and setting (see Discussion sections of Pangborn, Witherly, & Jones, 1979 and Sahakian et aI., 1981); however, their importance in obtaining a salivation response has not yet been determined. WHAT DOES SALIVATION MEASURE?
Ultimately the theoretical issue(s) of concern must determine the methodology. So the fundamental question is what the salivation response to food-related stimuli can be used to measure. Wooley and Wooley (1973) suggested that salivation to the sight and thought of food be used to measure "appetite" for food. They treat this variable as an individual's state.ofmotivation to eat-a behavioural disposition or desire (Bolles, 1980) increased by food deprivation, by palatable food and by hope of eating and decreased by anxiety Drs Trevor Robbins, Paul Fray and David Booth are thanked for their helpful comments. Requests for reprints should be sent to Dr B. J. Sahakian, Dunn Clinical Nutrition Centre, M. R. C. Dunn Nutrition Unit, Addenbrooke's Hospital, Trumpington Street, Cambridge CB2 lQE, England. 0195-6663/81/040386+04 $02'00/0
f(
1981 Academic Press Inc. (London) Limited
No
Yes
Yes
Yes
Yes
Yes b
Food presented (pizza)
Yes d
Food presented (individual's preferred food)
Obese + non-obese women
Guy-Grand & Goga
Yese
Food presented (pizza)
Obese + non-obese
No
Yes i See footnotes on following page.
No i
Yes i
Yes g
Food" presented (pizza)
Taste of distilled water, chicken or beef broths
Yes f
Obese women
Rosen
Non-obese men + women
Herman, Polivy, Klajner, Pangborn & & Esses Chung
Salivation response correlated with ratings
Yes C
Food presented
Obese women
Non-obese Non-obese Non-obese men + women men + women men + women
Olfactory Food names only only (honey, (menulemon, or no food) bovril vapour)
Durrant
Herman/Polivy Scale
Desire to eat
Hunger sensations
Salivation response
Eliciting foodrelated stimuli
Subjects
Authors
Booth & Fuller
Brummer & Pudel
Blundell & Freeman
1
Summary offorum participants' findings on salivation and appetite
TABLE
Yes k
No
Yes
Food presented (steak, potato, tomato and mushroom)
Non-obese men + women
Sahakian, Lean, Robbins, & James (1981)
Yes I
Yes
Yes h
Food presented (different types) or imagined
Obese + non-obese
Wooley & Wooley
388
B. J. SAHAKIAN
aSubjects were not allowed to eat pizza, but given the scheduled mean instead. bObtained the basic effect, but it was not affected by deprivation level nor consistent within subjects. cSalivation response was inversely related to energy content of a preload fed to hungry subjects, unless subjects already adapted to a low energy intake. Salivation not reliable from day to day. dSalivation responses of "dynamic" obese subjects greater than those of "static" obese or non-obese subjects. No correlation between food intake as assessed by dietetic interviews and either salivation or hunger ratings. e"Dieter"/"non-dieter" salivation difference negligible when food used was unpalatable. fparotid saliva measured. gSubjects adapted to a low energy intake salivated less in response to food. hDeprivation level (high or low calorie preload) affected the response of "restrained" but not "unrestrained" eaters. Within subjects salivation response was relatively stable. Unpalatable food did not produce salivation response. ipreload conditions. iDieters (restrained eaters) showed a greater salivation response than non-dieters (unrestrained eaters). kRestrained eaters showed a greater salivation response than unrestrained eaters. IUnrestrained eaters showed a greater salivation response than restrained eaters.
about temptation to break a diet, by prior ingestion of food, and by the action of appetite-suppressant drugs (Wooley & Wooley 1981). Hunger is another word for the same desire, although the attempt is sometimes made to restrict "hunger" to the eating motivation created by food deprivation or even to the allied sensations or physiological processes-correlatively restricting "appetite" to the effects of palatability on eating motivation. Some contributors follow these conventions, even attempting to impose them on subjects' ratings or assuming appetite to be a private state expressible only in ratings. However, other contributors nest the construct of appetite in the independent variables used by the Wooleys and/or in the dependent variable offood intake. Both rating procedures and salivation tests require validation against these variables if they are to be accepted as measures of appetite. Ifboth ratings and salivation express the same set of dispositions (even only in part) then the salivation response should correlate with the relevant ratings (Table 1). Furthermore, the question arises whether salivation, or indeed other cephalic responses (Powley, 1977), such as insulin secretion, can be more sensitive than some ratings (or even intake measurements) as an assessment of the disposition to eat (Table 1). Even if it cannot, a physiological expression of a motivational state can be more suitable than a verbal expression or a behavioural expression of the motivation, although this forum makes it quite clear that a validated salivation test would remain an instrument to be used with care and psychological circumspection, not as a supposedly physically operationalized and invariant objective handle on a behavioural state. The correlation between ratings and salivation depends on as yet unspecified variations in procedure, perhaps in both types of assessment. For example, while Blundell and Freeman (1981), Guy-Grand and Goga (1981), and Sahakian et al. (1981) found no correlation between salivation responses and ratings of hunger sensations, Durrant and Royston (1979) and Booth and Fuller (1981) in contrast report such correlations. Also, Sahakian et al. (1981) found that food appeal ratings did not correlate with salivation response, and yet Wooley and Wooley (1973) in an ad hoc condition in which unappealing food was presented, found a blockade ofthe increase in
COMMENTARY ON THE FORUM
389
salivation in response to food presentation. Certain of these variations mentioned above in regard to their importance in obtaining a salivation response may prove useful also in clarifying the conditions under which ratings of degree of hunger and of the appeal of the food stimulus are correlated with the size of the salivation response induced by food. In particular, the effect of palatability on salivation will depend on whether the subject is on a diet or not (Herman, Polivy, Klajner, &Esses, 1981; Wooley, & Wooley, 1981). CONCLUSION
It seems that considerably more systematic attention to the cognitive and sensory processes involved in both salivation and appetite ratings will be needed before the exact value of salivation (or the ratings) as a measure of appetite is determined. Experiments which measure the amount of food ingested by dieters and non-dieters after measuring salivation, as well as other cephalic responses, are clearly warranted. What is clear already is that the study of salivation responses in relation to appetite will be highly productive of improvements of our understanding of the control of eating, both generally and when clinically desirable in particular. REFERENCES
Blundell, J. E., & Freeman, D. G. Sensitivity of stimulus-induced-salivation (SIS) hunger ratings and alliesthesia to a glucose load: SIS as a measure of specific satiation. Appetite: Journalfor Intake Research, 1981,2,373-375. Bolles, R. C. Historical note on the term "appetite". Appetite: Journalfor Intake Research, 1980, 1,3-6. Booth, D. A., & Fuller, J. Salivation as a measure of appetite: a sensitivity issue. Appetite Journal for Intake Research, 1981, 2, 370-375. Brummer, A., & Pudel, V. E. An attempt to demonstrate reliable salivary increases in the hungry state. Appetite: Journal for Intake Research, 1981,2, 376-379. Durrant, M. Salivation: a useful research tool? Appetite: Journal for Intake Research, 1981,2, 362-365. Durrant, M., & Royston, P. Short-term effects of energy density on salivation, hunger and appetite in obese subjects. International Journal of Obesity, 1979, 3, 335-347. Guy-Grand, B., & Goga, H. Salivation in static or dynamic obesity. Appetite Journalfor Intake Research, 1981,2, 351-355. Herman, C. P., Polivy , J., Klajner, F., & Esses, V. M. Salivation in dieters and non-dieters. Appetite: Journal for Intake Research, 1981, 2, 356-361. Pangborn, R. M., & Chung, C. M. Paratoid salivation in response to sodium chloride and monosodium glutamate in water and in broths. Appetite: Journalfor Intake Research, 1981, 380-385. Pangborn, R. M., Witherly, S. A., & Jones, F. Parotid and whole-mouth secretion in response to viewing, handling and sniffing food. Perception, 1979,8, 339-346. Powley, T. L. The ventromedial hypothalamic syndrome, satiety and a cephalic phase hypothesis. Psychological Review, 1977, 84, 89-126. Rosen, J. C. Effects oflow-calorie dieting and exposure to diet-prohibited food on appetite and behaviour. Appetite: Journal for Intake Research, 1981,2, 366-369. Sahakian, B.J., Lean, M. E.J. Robbins, T. W., & James, W. P. T. Salivation and insulin secretion in response to food in non-obese men and women. Appetite: Journalfor Intake Research, 1981, 2, 209-216. Wooley, S. c., & Wooley, O. W. Salivation to the sight and thought of food: a new measure of appetite. Psychosomatic Medicine, 1973,35, 136-142. Wooley, S. c., & Wooley, O. W. Relationship of salivation in humans to deprivation, inhibition and the encephalization of hunger. Appetite: Journalfor Intake Research, 1981,2,331-350.
Received 23 August, 1981
Salivation and Appetite: Commentary on the Forum B. J. SAHAKIAN M. R. C. Dunn Clinical Nutrition Centre, Cambridge, U.K.
The purpose of this forum was to assess experimenters' varied experiences of the salivation response to food-related stimuli and the usefulness of salivation as a measure of appetite. Table 1 collates a number of aspects ofthe findings presented by participants in the forum. Earlier data have been summarized in the Wooleys' keynote review. Several interesting questions remain to be answered. Is
THERE AN IDEAL SALIVATION TEST PROCEDURE?
From the majority of the contributions (Table 1), it might be concluded that saliva should be collected on one or perhaps two dental rolls over as little as 1 or perhaps 2 min. However, other methods, such as the collection of saliva in cups (Sahakia.n, Lean, Robbins, & James, 1981) may prove equally successful and less obtrusive. There is reason to suggest that frequent or numerous tests disrupt salivation. On the other hand, the contributions in this forum by Brummer and Pudel, and by Durrant suggest that a single, simply administered procedure cannot always be relied on to give a consistent salivation response in all individuals and indeed, certain individuals may fail to show a response. Other variations in procedure have been discussed-such as whether the food is physically present or only symbolically represented, whether the food presentation allows the subject both to see and smell the food, whether or not the subject is on a diet, whether or not the subject is instructed to consume the food following saliva collection, and the experimental atmosphere and setting (see Discussion sections of Pangborn, Witherly, & Jones, 1979 and Sahakian et aI., 1981); however, their importance in obtaining a salivation response has not yet been determined. WHAT DOES SALIVATION MEASURE?
Ultimately the theoretical issue(s) of concern must determine the methodology. So the fundamental question is what the salivation response to food-related stimuli can be used to measure. Wooley and Wooley (1973) suggested that salivation to the sight and thought of food be used to measure "appetite" for food. They treat this variable as an individual's state.ofmotivation to eat-a behavioural disposition or desire (Bolles, 1980) increased by food deprivation, by palatable food and by hope of eating and decreased by anxiety Drs Trevor Robbins, Paul Fray and David Booth are thanked for their helpful comments. Requests for reprints should be sent to Dr B. J. Sahakian, Dunn Clinical Nutrition Centre, M. R. C. Dunn Nutrition Unit, Addenbrooke's Hospital, Trumpington Street, Cambridge CB2 lQE, England. 0195-6663/81/040386+04 $02'00/0
f(
1981 Academic Press Inc. (London) Limited
No
Yes
Yes
Yes
Yes
Yes b
Food presented (pizza)
Yes d
Food presented (individual's preferred food)
Obese + non-obese women
Guy-Grand & Goga
Yese
Food presented (pizza)
Obese + non-obese
No
Yes i See footnotes on following page.
No i
Yes i
Yes g
Food" presented (pizza)
Taste of distilled water, chicken or beef broths
Yes f
Obese women
Rosen
Non-obese men + women
Herman, Polivy, Klajner, Pangborn & & Esses Chung
Salivation response correlated with ratings
Yes C
Food presented
Obese women
Non-obese Non-obese Non-obese men + women men + women men + women
Olfactory Food names only only (honey, (menulemon, or no food) bovril vapour)
Durrant
Herman/Polivy Scale
Desire to eat
Hunger sensations
Salivation response
Eliciting foodrelated stimuli
Subjects
Authors
Booth & Fuller
Brummer & Pudel
Blundell & Freeman
1
Summary offorum participants' findings on salivation and appetite
TABLE
Yes k
No
Yes
Food presented (steak, potato, tomato and mushroom)
Non-obese men + women
Sahakian, Lean, Robbins, & James (1981)
Yes I
Yes
Yes h
Food presented (different types) or imagined
Obese + non-obese
Wooley & Wooley
388
B. J. SAHAKIAN
aSubjects were not allowed to eat pizza, but given the scheduled mean instead. bObtained the basic effect, but it was not affected by deprivation level nor consistent within subjects. cSalivation response was inversely related to energy content of a preload fed to hungry subjects, unless subjects already adapted to a low energy intake. Salivation not reliable from day to day. dSalivation responses of "dynamic" obese subjects greater than those of "static" obese or non-obese subjects. No correlation between food intake as assessed by dietetic interviews and either salivation or hunger ratings. e"Dieter"/"non-dieter" salivation difference negligible when food used was unpalatable. fparotid saliva measured. gSubjects adapted to a low energy intake salivated less in response to food. hDeprivation level (high or low calorie preload) affected the response of "restrained" but not "unrestrained" eaters. Within subjects salivation response was relatively stable. Unpalatable food did not produce salivation response. ipreload conditions. iDieters (restrained eaters) showed a greater salivation response than non-dieters (unrestrained eaters). kRestrained eaters showed a greater salivation response than unrestrained eaters. IUnrestrained eaters showed a greater salivation response than restrained eaters.
about temptation to break a diet, by prior ingestion of food, and by the action of appetite-suppressant drugs (Wooley & Wooley 1981). Hunger is another word for the same desire, although the attempt is sometimes made to restrict "hunger" to the eating motivation created by food deprivation or even to the allied sensations or physiological processes-correlatively restricting "appetite" to the effects of palatability on eating motivation. Some contributors follow these conventions, even attempting to impose them on subjects' ratings or assuming appetite to be a private state expressible only in ratings. However, other contributors nest the construct of appetite in the independent variables used by the Wooleys and/or in the dependent variable offood intake. Both rating procedures and salivation tests require validation against these variables if they are to be accepted as measures of appetite. Ifboth ratings and salivation express the same set of dispositions (even only in part) then the salivation response should correlate with the relevant ratings (Table 1). Furthermore, the question arises whether salivation, or indeed other cephalic responses (Powley, 1977), such as insulin secretion, can be more sensitive than some ratings (or even intake measurements) as an assessment of the disposition to eat (Table 1). Even if it cannot, a physiological expression of a motivational state can be more suitable than a verbal expression or a behavioural expression of the motivation, although this forum makes it quite clear that a validated salivation test would remain an instrument to be used with care and psychological circumspection, not as a supposedly physically operationalized and invariant objective handle on a behavioural state. The correlation between ratings and salivation depends on as yet unspecified variations in procedure, perhaps in both types of assessment. For example, while Blundell and Freeman (1981), Guy-Grand and Goga (1981), and Sahakian et al. (1981) found no correlation between salivation responses and ratings of hunger sensations, Durrant and Royston (1979) and Booth and Fuller (1981) in contrast report such correlations. Also, Sahakian et al. (1981) found that food appeal ratings did not correlate with salivation response, and yet Wooley and Wooley (1973) in an ad hoc condition in which unappealing food was presented, found a blockade ofthe increase in
COMMENTARY ON THE FORUM
389
salivation in response to food presentation. Certain of these variations mentioned above in regard to their importance in obtaining a salivation response may prove useful also in clarifying the conditions under which ratings of degree of hunger and of the appeal of the food stimulus are correlated with the size of the salivation response induced by food. In particular, the effect of palatability on salivation will depend on whether the subject is on a diet or not (Herman, Polivy, Klajner, &Esses, 1981; Wooley, & Wooley, 1981). CONCLUSION
It seems that considerably more systematic attention to the cognitive and sensory processes involved in both salivation and appetite ratings will be needed before the exact value of salivation (or the ratings) as a measure of appetite is determined. Experiments which measure the amount of food ingested by dieters and non-dieters after measuring salivation, as well as other cephalic responses, are clearly warranted. What is clear already is that the study of salivation responses in relation to appetite will be highly productive of improvements of our understanding of the control of eating, both generally and when clinically desirable in particular. REFERENCES
Blundell, J. E., & Freeman, D. G. Sensitivity of stimulus-induced-salivation (SIS) hunger ratings and alliesthesia to a glucose load: SIS as a measure of specific satiation. Appetite: Journalfor Intake Research, 1981,2,373-375. Bolles, R. C. Historical note on the term "appetite". Appetite: Journalfor Intake Research, 1980, 1,3-6. Booth, D. A., & Fuller, J. Salivation as a measure of appetite: a sensitivity issue. Appetite Journal for Intake Research, 1981, 2, 370-375. Brummer, A., & Pudel, V. E. An attempt to demonstrate reliable salivary increases in the hungry state. Appetite: Journal for Intake Research, 1981,2, 376-379. Durrant, M. Salivation: a useful research tool? Appetite: Journal for Intake Research, 1981,2, 362-365. Durrant, M., & Royston, P. Short-term effects of energy density on salivation, hunger and appetite in obese subjects. International Journal of Obesity, 1979, 3, 335-347. Guy-Grand, B., & Goga, H. Salivation in static or dynamic obesity. Appetite Journalfor Intake Research, 1981,2, 351-355. Herman, C. P., Polivy , J., Klajner, F., & Esses, V. M. Salivation in dieters and non-dieters. Appetite: Journal for Intake Research, 1981, 2, 356-361. Pangborn, R. M., & Chung, C. M. Paratoid salivation in response to sodium chloride and monosodium glutamate in water and in broths. Appetite: Journalfor Intake Research, 1981, 380-385. Pangborn, R. M., Witherly, S. A., & Jones, F. Parotid and whole-mouth secretion in response to viewing, handling and sniffing food. Perception, 1979,8, 339-346. Powley, T. L. The ventromedial hypothalamic syndrome, satiety and a cephalic phase hypothesis. Psychological Review, 1977, 84, 89-126. Rosen, J. C. Effects oflow-calorie dieting and exposure to diet-prohibited food on appetite and behaviour. Appetite: Journal for Intake Research, 1981,2, 366-369. Sahakian, B.J., Lean, M. E.J. Robbins, T. W., & James, W. P. T. Salivation and insulin secretion in response to food in non-obese men and women. Appetite: Journalfor Intake Research, 1981, 2, 209-216. Wooley, S. c., & Wooley, O. W. Salivation to the sight and thought of food: a new measure of appetite. Psychosomatic Medicine, 1973,35, 136-142. Wooley, S. c., & Wooley, O. W. Relationship of salivation in humans to deprivation, inhibition and the encephalization of hunger. Appetite: Journalfor Intake Research, 1981,2,331-350.
Received 23 August, 1981