Effects of deprivation on salivary flow in the apparent absence of food stimuli

Apprtire, 1988. 20, 143-147

Effects of Deprivation on Salivary Apparent Absence of Food Stimuli JOSEPH

J. FRANCHINA

Department of Psychology, Virginia Polytechnic Institute

and KRISTINE

Flow

in the

L. SLANK

and State University

Salivation performance in the absence of food-related stimuli was measured with an absorbent technique in 19 subjects under no (O-1 h) and moderate (4-6 h) levels of food deprivation. Overall, salivation was reliably (p < 0.05) greater the higher the hours of deprivation. Results also revealed a reliable positive correlation between hours of deprivation and subjective ratings of hunger. For subjects whose hunger ratings coincided with hours of deprivation, analysis of the salivation data yielded highly reliable (p < 0.01) differences due to deprivation/hunger. For subjects who reported the same level of hunger at different hours of deprivation, there were no reliable differences in salivation due to deprivation.

INTRODUCTION

Salivation to the sight and thought of food is among the first of a series of cephalic responses which antecede digestion and, often, the oral acceptance of food (Powley, 1977). Because of its preingestional character, salivation was suggested (Wooley & Wooley, 1973) as a measure of appetite, the individual’s motivation or desire to eat (Bolles, 1980). According to Spiker and Rodin (1981), if salivation is to be a valid measure of appetite, variables which affect eating behaviour, such as hours of food deprivation and food palatability (Hill et al., 1984), should affect salivary responding. Wooley and

Wooley (1973) have reported that increasing hours of food deprivation reliably increased salivation to the sight of palatable foods, and Wooley et al. (1976 a) reported that deprivation reliably enhanced salivation in the presence and in the absence of food cues. Conversely, however, Brummer and Pudel(l981) and Christensen and Navazesh ( 1984) reported no reliable differences between deprived and sated subjects in salivation to the sight of food. These inconsistent findings could be due to procedural differences among the studies, as Christensen

studies (Brummer

and Navazesh

(1984) contend.

Nevertheless,

three of these

& Pudel, 1981; Wooley & Wooley, 1973; Wooley et al., 1976 a) used

similar absorbent measurement procedures (dental rolls) and comparable moderate levels of deprivation; and all four studies used at least one similar food cue (pizza).

These data were presented at the meeting of the Southeastern Psychological March 1986. Requests for reprints should be addressed to: J. J. Franchina, Department Polytechnic Institute and State University, Blacksburg, VA 24061. U.S.A. 0195-6663.:88!020143+05

$03GO/O

Association,

Orlando,

of Psychology,

Virginia

7?; 1988 Academic

Press Limited

144

J. J. FRANCHINA

AND K. L. SLANK

Before inconsistent results are attributed to procedural differences, perhaps a more fundamental study of the effects of deprivation per se on salivation responding is warranted (Sahakian, 1981). Such a study seems warranted especially in view of the finding of Wooley et al. (1976 a) that reliable deprivation effects occurred on baseline trials on which no food was present. Prior studies of deprivation effects on salivation have measured responding at food presentation and typically obtained pretest (baseline) measures of salivation without food present (e.g., Brummer & Pudel, 1981; Wooley et al., 1976a). It is possible that deprivation effects occur because deprivation influences the capability of food cues to elicit salivation. On the other hand, deprivation may act as a dispositional variable which directly determines salivation whether food is present or not. If so, reported differences in salivation to food stimuli between low- and high-deprived subjects (e.g., Wooley & Wooley, 1973) may not necessarily reflect the influence of deprivation on the attractiveness of food cues. These differences may simply be deprivation’s effects on salivation per se. To provide this information the present experiment used a withinsubjects design and investigated salivation under no (O-1 h) and moderate (4-6 h) deprivation in four test sessions (five trials per session) over a 2-week period. No foodrelated cues were ever presented. Deprivation levels were chosen to approximate those of studies (e.g., Wooley & Wooley, 1973: Wooley et al., 1976a; Hodgson & Green, 1980) which reported reliable deprivation effects on salivation to food cues. We know of no data on the effects of deprivation on salivation in which systematic (repeated) assessment of salivation occurred in the absence of food cues. METHOD

Subjects

Subjects were ten female and nine male student volunteers in the normal weight range and with no reported history of eating problems. Subjects were remunerated for their participation in the study. Design and Procedures

Salivation measures were obtained between 1600 and 1800 hrs on 2 days of the week, typically Monday and Thursday, for 2 consecutive weeks. For subjects who were tested at 1800 hrs, O-1 h had elapsed since their most recent meal (no deprivation condition). For subjects tested at 1600 hrs, 4-6 h had elapsed since their most recent meal (deprivation condition). All subjects were tested under both conditions in each week, thereby providing a within-subject manipulation of food deprivation, repeated over the 2 weeks. Ten randomly selected subjects received salivation testing under a sequence of deprivation, no deprivation, no deprivation, deprivation across the 2 weeks; nine subjects received testing in a sequence of no deprivation, deprivation, deprivation, no deprivation. For a test session, subjects were seated in an easy chair in a semi-darkened room. They filled out a questionnaire to indicate (a) the time since their most recent meal, (b) whether they had a snack since that meal, and (c) how hungry they were feeling on a scale from 0 (not at ail hungry) to 5 (extremely hungry). Each subject was familiarized with the use of the dental rolls (sample trial) prior to testing. For a test trial, the subject was asked to swallow and then insert a 1.5 in. dental roll, laterally, into each side of the lowerjaw between teeth and gums. The subject was urged

SALIVATION

145

AND DEPRIVATION

to relax, keep his/her jaw and head still, and avoid swallowing. Each test trial lasted 2 min. At the end of a trial, the subject removed the dental rolls and placed them into a sealable plastic bag. During the intertrial interval (2 min) the experimenter engaged the subject in casual conversation. There were five test trials per session. The performance measure was amount salivated, calculated as the difference to the nearest 0.1 mg in the weight of the dental rolls (and container) from pretest to post-test.

RESULTS

Figure 1 shows mean amount (g) of salivation on the sample trial and on trials I 5 for deprivation and no deprivation conditions. Because the same difference in salivation due to deprivation occurred in weeks 1 and 2, the data were collapsed across weeks in this figure. Salivation was lower in week 2 than that in week 1. Figure 1 shows that, over trials 1-5, deprivation yielded greater salivation than did no deprivation. Salivary flow decreased over test trials for both deprivation conditions. ANOVA over all the test data of both weeks yielded reliable effects for Deprivation, Test Trials and Weeks but not for any interactions, F( l/18, 4/72 and l/18) =4.44, 4.90 and 4.79; p < 0.05, < 0.002 and
T

I

I

I

I

I

I

s

I

2

3

4

5

T

Tr1&

FIGURE 1. Mean salivation groups under deprivation, O--a,

(g) in 2-min periods for the sample trial (S) and trials I 5. for and no deprivation,

0~~~0,

conditions.

146

J. J. FRANCHINAAND K. L. SLANK

they were in the same state of hunger despite being under different hours of deprivation in a week. ANOVA over these data yielded no reliable effects for Deprivation (F < l), Trials [F(4,56) = 2.44, p < 0061 or Deprivation x Trials (F < 1). In other cases (N = 23), subjects’ hunger ratings paralleled deprivation. For these subjects, salivation was greater for the deprivation/hunger rating condition than for the no deprivation/hunger condition: Deprivation/Hunger Level and Trials, F(1/22 and 4/88) =7.05 and 3.13, ~~0.01 and 0.02, respectively.

DISCUSSION In this experiment, increasing hours without food reliably increased salivary flow in the absence of food stimuli. Deprivation times were selected to approximate those of studies (e.g., Wooley & Wooley, 1973; Wooley et al., 1976 a; Hodgson & Greene, 1980) which reported reliable deprivation effects at food presentation. The present findings support the conclusions of those studies. In this study, subjects received no information about food presentation; no expectancy to eat was established; no food-related cues were presented. The present data therefore suggest that salivation was due to the physiological state of hunger, a conclusion which concurs with that of Wooley et al. (1976 a). If deprivation influences salivation in the absence of food cues, the use of baseline salivation may be unsuitable as a comparison to assess the role of deprivation on appetitive responding to food stimuli (Wooley et al. 1976a, p. 192). The present results and those of Wooley et al. (1976 a) suggest that future studies of deprivation effects on salivation to food cues might include groups who are tested without food present. The present study did not assess the possible influence of cognitive mediation (e.g., images of food) on salivary flow. White (1978) reported that images of food reliably influenced salivary flow; salivation was reliably greater the more preferred the imagined food was. Staats and Hammond (1972) reported that salivary flow to food words was reliably greater in deprived than in non-deprived subjects. At the start of a test session in the present study, subjects indicated the time since their last meal, whether they had had a snack, and how hungry they were. If providing this information occasioned thoughts of food then cognitive events as well as deprivation effects may be implicated in the present results. In any case, post hoc analyses suggested that the influence of deprivation may have been qualified by subjective feelings of hunger. Hunger rating scores generally increased with deprivation time. However, there was no reliable effect of deprivation on salivation for subjects who reported the same hunger rating under different deprivation levels whereas a highly reliable (p < 001) deprivation effect occurred for subjects whose hunger ratings coincided with deprivation level. These findings may reflect the subjects’ awareness of their physiological condition resulting from deprivation (e.g. an empty stomach) or the subjects’ labelling of their internal state on the basis of contextual cues-namely, knowing the time since they last ate (Schachter & Singer, 1962). Present data provide no basis for choice between these alternatives. In any case, this study suggests that salivary flow is a sensitive index of events related to food deprivation, whether these events are physiological hunger signals or cognitive consequences of time without food.

147

SALIVATION AND DEPRIVATION REFERENCES

Bolles, R. C. (1980) Historical note on the term “appetite”. Appetite, I, 3-6. Brummer, A. & Pudel, V. E. (1981) An attempt to demonstrate reliable salivary increases in the hungry state. Appetite, 2, 376-379. Christensen, C. M. & Navazesh, M. (1984) Anticipatory salivary flow to the sight of different foods. Appetite, 5, 307-315. Hill, A. J., Magson, L. D. & Blundell, J. E. (1984) Hunger and palatability: Tracking ratings of subjective experience before, during and after the consumption of preferred and less preferred foods. Appetite, 5, 361-371. Hodgson, R. J. &Greene, J. B. (1980) The saliva priming effect, eating speed and the measurement of hunger. Behavior Research and Therapy, 18, 2433247. Powley, T. L. (1977) The ventromedial hypothalamic syndrome, satiety and a cephalic phase hypothesis. Psychological Review, 84, 89-126. Sahakian, B. J. (1981) Salivation and appetite: Commentary on the forum. Appetite, 2,386389. Schachter, S. & Singer, J. E. (1962) Cognitive, social, and physiological determinants of emotional state. Psychological Review, 69, 379-399. Spitzer, L. & Rodin, J. (1981) Human eating behavior: A critical review of studies in normal weight and overweight individuals. Appetite, 2, 293-329. Staats, A. W. & Hammond, 0. W. (1972) Natural words as physiological conditioned stimuli: Food-word-elicited salivation and deprivation effects. Journal of Experimental Psychology, 96, 206-208.

White, K. D. (1978) Salivation:

The significance

of imagery

in its voluntary

control.

Psychophysiology, 15, 196-203.

Wooley, 0. W., Wooley, S. C. & Dunham, R. B. (1976 a) Deprivation, expectation and threat: Effects on salivation in the obese and the nonobese. Physiology and Behavior, 17, 187-193. Wooley, 0. W., Wooley, S. C. & Williams, B. S. (1976 b) Salivation as a measure of appetite: Studies of the anorectic effects of calories and amphetamine. In D. Novin, W. Wyrwicka & G. Bray (Eds.), Hunger: Basic mechanisms and clinical implications. Pp. 421429. New York: Raven Press. Wooley, S. C. & Wooley, 0. W. (1973) Salivation to the thought and sight offood: A new measure of appetite. Psychosomatic Medicine, 35, 136- 142. Received

17 June

1987, revision 7 January

1988