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Hunger induced changes in food choice. When beggars cannot be choosers even if they are allowed to choose
Appetite 54 (2010) 603–606
Contents lists available at ScienceDirect
Appetite journal homepage: www.elsevier.com/locate/appet
Short communication
Hunger induced changes in food choice. When beggars cannot be choosers even if they are allowed to choose Atilla Hoefling *, Fritz Strack Department of Psychology, University of Wu¨rzburg, Ro¨ntgenring 10, D-97070 Wu¨rzburg, Germany
A R T I C L E I N F O
A B S T R A C T
Article history: Received 16 September 2009 Received in revised form 23 February 2010 Accepted 25 February 2010
The present work was to examine the influence of food deprivation on food choice. For this purpose hungry versus satiated subjects were presented with a series of choices between two snacks in a complete block design of pairwise comparisons. Snacks systematically varied with respect to subjects’ idiosyncratic taste preferences (preferred versus un-preferred snack), portion size (large portion versus very small portion), and availability in terms of time (immediately available versus available only after a substantial time delay). Food choices were analyzed with a conjoint analysis which corroborated the assumption that food deprivation decreases the relative importance of taste preference and increases the importance of immediate availability of food. ß 2010 Elsevier Ltd. All rights reserved.
Keywords: Food deprivation Food choice Food preferences Taste preferences Conjoint analysis
Prior research on human food choice revealed that good flavor and sensory appeal seem to be of major importance when deciding which foods to pick for consumption, and which foods to reject (e.g., Eertmans, Baeyens, & Van den Bergh, 2001; Martins & Pliner, 1998, 2005; Rozin & Zellner, 1985; Scheibehenne, Miesler, & Todd, 2007; Stafleu, de Graaf, van Staveren, & Schroots, 1991; Steptoe, Pollard, & Wardle, 1995). In addition, factors like health and weight concerns, ethical considerations, convenience, price, familiarity, and anticipated emotional effects were found to be important decision criteria for human food choices, too (e.g., Candel, 2001; Connors, Bisogni, Sobal, & Devine, 2001; Eertmans, Victoir, Vansant, & Van den Bergh, 2005; Green, Draper, & Dowler, 2003; Marquis, 2005; Martins & Pliner, 1998; Roininen, La¨hteenma¨ki, & Tuorila, 1999; Roininen et al., 2001; Rozin & Zellner, 1985; Scheibehenne et al., 2007; Stafleu et al., 1991; Steptoe et al., 1995; Zandstra, de Graaf, & Van Staveren, 2001). Noteworthy, past research also yielded that there exist stable interindividual differences in the importance of these factors (e.g., Glanz, Basil, Maibach, Goldberg, & Snyder, 1998; Lindeman & Sirelius, 2001; Oakes & Slotterback, 2001; Pilgrim, 1957; Prescott, Young, O’Neill, Yau, & Stevens, 2002; Rappoport, Peters, Downey, McCann, & Huff-Corzine, 1993; Wardle et al., 2004). The influence of food deprivation on food choice It was acknowledged elsewhere that the importance of a given factor might also vary as a function of contextual cues. In
* Corresponding author. E-mail address: hoefl[email protected] (A. Hoefling). 0195-6663/$ – see front matter ß 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.appet.2010.02.016
particular, it was speculated that an organism’s physiological need state might provide a contextual cue that has the potential to increase the relative importance of nutritional value (compared to other food attributes like price) in the realm of food choice (Scheibehenne et al., 2007). This reasoning is in line with the commonsensical assumption that the eating behavior of hungry organisms should be determined by physiological demands rather than by psychological influences (Herman & Polivy, 1984; Jacobs & Sharma, 1969; Nisbett, 1972), which is also reflected in the proverb ‘‘Beggars cannot be Choosers’’. To put it in simple terms, immediate satiation should matter more for the food deprived organism than exquisite flavor or gourmet-like presentation. Despite having face validity the above mentioned assumptions are anecdotal and were never put under systematic experimental investigation to the present day. Some relevant studies yielded that food deprived subjects were more willing than satiated subjects to consume even unpalatable (bitter) foods when nothing else was available, thereby giving at best a first hint that the importance of certain food attributes (e.g., good flavor) may be moderated by physiological need states (e.g., Bellisle, Lucas, Amrani, & Le Magnen, 1984; Desor, Maller, & Green, 1977; Hill, 1974; Hill & McCutcheon, 1975; Nisbett, 1968; but see also Kauffman, Herman, & Polivy, 1995 or Pliner, Herman, & Polivy, 1990 for conflicting results and for an integration of these incompatible findings). Noteworthy, the influence of food deprivation on the relative importance of food attributes like palatability or nutrient content was never assessed directly before. To bridge this gap, a computerized food choice task was conducted, and relative weights of three critical food attributes were computed in a conjoint analysis. In short, different snack options (two at a time) were presented on a
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computer screen that varied with respect to subjects’ idiosyncratic taste preferences (preferred versus un-preferred snack), portion size (very small portion versus large portion), and availability in terms of time (immediately available versus available only after a delay of 90 min). Subjects were asked to choose their preferred snack option across a number of different trials and the relative importance for each snack attribute was computed separately for hungry and satiated subjects on the basis of these choices. Hypotheses. It is assumed that the utility derived from good flavor decreases for the starving organism, whereas the utility derived from immediate availability and large portion size increases. As a result, the relative part worth (or weighting) of idiosyncratic taste preference in a conjoint analysis should be significantly smaller for food deprived participants than for satiated participants, whereas the importance of both, (large) portion size and (short) waiting time should be larger. Furthermore, it was expected that the utility structure within each experimental group should be affected by food deprivation, too. That is, idiosyncratic taste preference (compared to portion size and waiting time) should be more important for satiated subjects, but less important for food deprived subjects.
lunch immediately before the experiment (which was said to heighten their blood glucose level). Satiated participants were free to eat what they want, but were instructed to have at least a warm main course, a desert and a non-alcoholic drink. Experimental sessions started at noon or 1:30 p.m., and participants (groups up to three persons who were tested at a separate table) signed a consent form and reported their current mood before rank ordering 8 different, customary snacks according to their momentary taste preference. Then, subjects completed the aforementioned measure of concentration followed by the computerized food choice task (paired comparisons) and a set of demographic questions including subjective feelings of hunger serving as a manipulation check. Finally, subjects were probed for suspicion and debriefed Mood assessment In order to ensure that a priori mood differences are not responsible for any of the reported findings (food deprived subjects might be in a worse mood due to their state of deprivation), subjects were asked how strongly they agree with the statement ‘‘I am in a good mood right now’’ on a scale ranging from 1 (totally disagree) to 6 (totally agree) at the beginning of the session.
Methods Participants and design Fifty-nine undergraduate psychology students (43 female) at the University of Wu¨rzburg (Germany) took part in an experiment that was introduced as consisting of several studies including one experiment on the effects of blood glucose levels on concentration (concentration test) and one experiment on consumer psychology. In fact, the only purpose of the concentration test (for details see Brickenkamp, 1962; Oswald, Hagen, & Brickenkamp, 1997) was to cover the manipulation of need state and to minimize demand effects that might arise when subjects form an explicit link between their need state and the food choice task. Hence it will not be reported any further. All subjects received course credits for participation. Aside from need state, three critical attributes of experimental foods were manipulated within a food choice task, resulting in a 2 (need state: deprived versus satiated) 2 (idiosyncratic taste preference: preferred snack versus non-preferred snack) 2 (portion size: very small portion versus large portion) 2 2 (availability: immediately available versus available only after 90 min delay) mixed factorial design with need state being manipulated between participants. To minimize the role of health and weight concerns (that were not of interest in the present study) only normal eating, normal weight subjects were included. That is, persons being on a diet during the period of data collection or having food-relevant allergies were not invited for participation, and subjects with a Body Mass Index (BMI) below 17.5 (n = 1), or above 25 (n = 5) were excluded from the analyses. Vegetarians were included because no food stimuli were presented that included meat. Two more subjects had to be excluded because of computer errors. The resulting sample consisted of 14 men and 37 women, aged between 18 and 41 years (M = 21.64, SD = 3.76). Experimental groups did not differ in the percentage of women (hungry: 74.1% versus satiated: 70.8%), x2 (1; N = 51) < 1, BMI (Mhungry = 21.46, SD = 2.03 versus Msatiated = 21.35, SD = 1.92), t(49) < 1, or age (Mhungry = 21.30, SD = 2.54 versus Msatiated = 22.08, SD = 4.75), t(49) < 1. Procedure and materials Procedure Participants were either asked to refrain from eating for 15 h (which was said to lower their blood glucose level), or to have
Rank ordering procedure To vary taste preference on an idiosyncratic level (see following paragraph) participants rank ordered 8 different, customary snacks according to their momentary preference from 1 (most preferred snack) to 8 (least preferred snack). The snacks were potato chips, salty peanuts, M&M’s chocolate peanuts, gummy bears, milk chocolate, salty crackers, cheese sticks, and butter muffins. Food choice task (paired comparisons) Paired comparisons were introduced as a study on consumer psychology consisting of several food choices. In each trial, subjects were instructed to choose between two snack options depicted on ‘‘randomly chosen photographs’’ on a computer screen. The position of each option on the screen (right versus left side) was determined randomly in each trial. In fact, each subject processed a specific computer file that included only photographs of the two snacks ranked on position 2 (preferred snack) and 6 (un-preferred snack) in the rank ordering procedure (manipulation of idiosyncratic taste preference). Extreme ranks were not selected in order to ensure that all critical features are related to each other in a compensatory manner, and that taste preference would not act as a ‘‘K.O.-criterion’’ in the conjoint analysis (see Backhaus, Erichson, Plinke, & Weber, 2003). Portion size was manipulated by photographing each snack on a plate under standardized conditions, both, in a small and large portion size version. The actual amount of food used for each version was determined in such a way that subjects from a separate pretest sample expected only the large portion of each snack to be filling, but not the small portion. Availability in terms of time was manipulated by giving written information on top of each photograph (immediately available versus available in 90 min). Systematically combining these three features of twofold gradation resulted in a total number of 8 different snack options that served as objects in a complete block design of 28 paired comparisons (Thurstone, 1927). Importantly, a snack option (or object, respectively) is defined as a photograph plus written information. Since all factors were discrete and of twofold gradation, the utility of the second parameter value represents the mere reciprocal of the first parameter value for each factor and was not relevant for further analysis (see SPSS, 2009). Thus, utility scores (uj) were only computed for the following specific food attributes (j): getting a favored snack, getting a large portion, and getting a snack immediately. In particular, utility scores were
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estimated for each subject separately by rank ordering all snack options (objects) according to the number of trials in which they had been preferred, and applying an Ordinary Least Squares regression algorithm on these ordinal data. That is, the part worth for each attribute (j) was computed as the difference between its mean rank and the unweighted mean rank of the respective factor. Afterwards, scores of relative importance (impj) were calculated P for each attribute (j) as 100 (uj/ uj) and aggregated for hungry and satiated subjects separately. Noteworthy, scores of relative importance represent percent-values that can be interpreted in an absolute manner. Hunger ratings Subjective feelings of hunger were reported on a scale ranging from 1 (not hungry at all) to 7 (very hungry) after the food choice task and served as a manipulation check. Albeit the exposure to food stimuli might have influenced subsequent hunger ratings, this positioning seemed most appropriate to prevent subjects from explicitly linking the hunger manipulation to the food choice task.
Fig. 1. Relative importance of idiosyncratic taste preference, (large) portion size, and (short) waiting time as a function of need state. Error bars indicate standard errors of the means.
Hunger ratings were analyzed with a simple t-test. As expected, food deprived participants (M = 5.56, SD = 1.50) reported stronger feelings of hunger than satiated participants (M = 2.54, SD = 1.82), t(49) = 6.77, p < .001, d = 1.81.
important than portion size or waiting time amongst hungry subjects. An inspection of Fig. 1 reveals that (for satiated subjects) idiosyncratic taste preference was indeed more important than (short) waiting time, t(23) = 3.73, p = .001, d = 1.32, or (large) portion size, t(23) = 2.02, p = .056, d = .75. Amongst hungry subjects this pattern disappeared but did not reverse. That is, taste preference was only slightly less important than portion size, t(23) = 2.02, p = .15, but not less important than waiting time, t < 1.
Preliminary analyses
Discussion
Self-reports of mood were analyzed with a simple t-test that yielded no a priori differences in mood between satiated subjects (M = 4.00, SD = 1.22) and food deprived subjects (M = 3.74, SD = 1.29), t(49) < 1. Consequently, this variable was discarded.
The results of the present study strongly corroborate the assumption that food deprivation decreases the importance of idiosyncratic taste preferences for the benefit of immediate availability in the realm of food choice. That is, compared to satiated participants, food deprived participants did not predominantly select a preferred snack but were more intent on getting anything to eat immediately. In sharp contrast, idiosyncratic taste preference was clearly the most important selection criterion amongst satiated subjects (see also Rozin & Zellner, 1985; Scheibehenne et al., 2007; Stafleu et al., 1991), who predominantly insisted on getting their favored snack and were willing to accept small portion sizes and long waiting times for it. The finding that all food features were nearly equally important for hungry subjects make clear that these priorities change, but do not completely reverse under conditions of starvation. That is, taste preferences become less important, but not insignificant in a state of food deprivation. One anonymous reviewer noted that the observed data pattern might also indicate that food choices may be based on different underlying mechanisms amongst food deprived and satiated subjects. That is, maybe hungry subjects make more complex and weighted decisions whereas satiated subjects base their choices just on taste as the most important criterion. It is true that both complex weighted additive mechanisms (e.g., Eertmans et al., 2005; Glanz et al., 1998; Rappoport et al., 1993; Scheibehenne et al., 2007), and simple heuristics (e.g., Connors et al., 2001; Scheibehenne et al., 2007) were put forward as adequate explanatory frameworks in the realm of food choice. However, given that it was not investigated to the present day if food deprivation has an impact on these procedural factors a pronouncement on this issue would go beyond the scope of the present paper and remains an issue for further research. Noteworthy, food deprived subjects’ willingness to choose unpreferred but immediately available foods in the present study is in line with previous studies on food intake yielding greater
Results Manipulation check
Relative importance of food attributes The relative importance of food attributes was analyzed with a 2 (need state: deprived versus satiated) 3 (food attribute: idiosyncratic taste preference versus portion size versus waiting time) mixed model ANOVA with need state being manipulated between subjects. The analysis revealed a significant main effect of food attribute, multivariate F(2,48) = 4.41, p = .017, d = .44, that was qualified by a significant need state food attribute interaction, multivariate F(2,48) = 6.21, p = .004, d = .52 (see Fig. 1). Follow-up t-tests were conducted to specify this interaction. In line with the central predictions it was found that the relative importance of idiosyncratic taste preference was greater for satiated subjects than for food deprived subjects,1 t(39.58) = 3.26, p = .002, d = .93. This indicates that it was more important for satiated subjects to get their favored snack than for food deprived subjects. In contrast, the relative importance of (short) waiting time was greater for food deprived subjects than for satiated subjects, t(49) = 2.52, p = .015, d = .71. The importance of (large) portion size however did not differ significantly between groups, t(49) = 1.27, p = .21. A second issue pertains to the trade-off between the three attributes within each experimental group. For this purpose, t-tests for dependent measures were conducted for food deprived and satiated subjects separately. To repeat, it was hypothesized that idiosyncratic taste preferences should be the most important selection criterion for satiated subjects, but should be less 1 Due to inhomogeneity of variances, a correction of degrees of freedom (df) was used.
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consumption of un-preferred foods amongst food deprived subjects (e.g., Bellisle et al., 1984; Desor et al., 1977; Hill, 1974; Hill & McCutcheon, 1975; Kauffman et al., 1995; Nisbett, 1968; Nisbett, Hanson, Harris, & Stair, 1973). However, while indicating that food deprived subjects will readily accept even un-preferred foods if nothing else is available, these latter studies are quite uninformative about the underlying mental mechanisms at the same time. By pitting taste preferences, portion size and availability in terms of time against each other in a conjoint analysis it was possible to determine more precisely why food deprived subjects do accept un-preferred foods more readily than satiated subjects. In essence, this might be the case because taste preferences loose their importance when being in a state of homeostatic dysregulation. With respect to the mental mechanisms underlying food deprived participants’ greater acceptance of unpalatable foods, the present study also relates to prior work on food deprivation and food related disgust. Hoefling et al. (2009) found for example that food deprived subjects exhibited weaker facial disgust reactions than satiated subjects when being confronted with disgusting foods despite evaluating them equally negative on an explicit level of information processing. It was concluded from this finding that food deprived participants’ greater consumption of unpalatable foods might also be due to an involuntary shift in their immediate affective reactions towards these foods. Although the un-preferred snacks in the present study were probably not rejected to the same extent as disgusting foods, the presented results are nevertheless informative about another possible mental mechanism underlying food deprived subjects’ greater acceptance and consumption of unpalatable foods, namely the change in the relative importance of mere palatability versus more functional food features. Based on the present findings it might also be interesting to examine if food deprivation does affect the importance of other factors (e.g., price, healthiness) too, and to compare restrained eaters/ eating disordered subjects’ food choices to those of normal eating subjects. Since determinants of food choices might be quite different in these samples, future studies might focus on the trade-off between the need for immediate satiation and health concerns under conditions of starvation and check whether restrained and normal eating subjects do value critical aspects of food to the same extent. References Backhaus, K., Erichson, B., Plinke, W., & Weber, R. (2003). Multivariate Analysemethoden. Eine anwendungsorientierte Einfu¨hrung. Berlin: Springer. Bellisle, F., Lucas, F., Amrani, R., & Le Magnen, J. (1984). Deprivation, palatability, and the micro-structure of meals in human subjects. Appetite, 5, 85–94. Brickenkamp, R. (1962). Aufmerksamkeits-Belastungs-Test (Test d2). Go¨ttingen: Hogrefe. Candel, M.J.J.M.. (2001). Consumers’ convenience orientation towards meal preparation: conceptualization and measurement. Appetite, 36, 15–28. Connors, M., Bisogni, C. A., Sobal, J., & Devine, C. M. (2001). Managing values in personal food systems. Appetite, 36, 189–200. Desor, J. A., Maller, O., & Green, L. S. (1977). Preference for sweet in humans: infants, children, and adults. In J. M. Weiffenbach (Ed.), Taste and development: the genesis of sweet preference (pp. 161–172). Washington: Government Printing Office. Eertmans, A., Baeyens, F., & Van den Bergh, O. (2001). Food likes and their relative importance in human eating behavior: review and preliminary suggestions for health promotion. Health Education Research, 16, 443–456. Eertmans, A., Victoir, A., Vansant, G., & Van den Bergh, O. (2005). Food-related personality traits, food choice motives and food intake: mediator and moderator relationships. Food Quality and Preferences, 16, 714–726. Glanz, K., Basil, M., Maibach, E., Goldberg, J., & Snyder, D. (1998). Why Americans eat what they do: taste, nutrition, cost, convenience, and weight control concerns as
influences on food consumption. Journal of the American Dietetic Association, 98, 1118–1126. Green, J. M., Draper, A. K., & Dowler, E. A. (2003). Short cuts to safety: risk and rules of thumb in accounts of food choice. Health, Risk & Society, 5, 33–52. Herman, C. P., & Polivy, J. (1984). A boundary model for the regulation of eating. In A. J. Stunkard & E. Stellar (Eds.), Eating and its disorders (pp. 141–156). New York: Raven Press. Hill, S. W. (1974). Eating responses of humans during dinner meals. Journal of Comparative and Physiological Psychology, 86, 652–657. Hill, S. W., & McCutcheon, N. B. (1975). Eating responses of obese and non-obese humans during dinner meals. Psychosomatic Medicine, 37, 395–401. Hoefling, A., Likowski, K. U., Deutsch, R., Ha¨fner, M., Seibt, B., Mu¨hlberger, A., et al. (2009). When hunger finds no fault with moldy corn: food deprivation moderates facial disgust reactions towards disgusting foods. Emotion, 9, 50–58. Jacobs, H. L., & Sharma, K. N. (1969). Taste versus calories: sensory and metabolic signals in the control of food intake. Annals of the New York Academy of Sciences, 157, 1084–1125. Kauffman, N. A., Herman, C. P., & Polivy, J. (1995). Hunger-induced finickiness in humans. Appetite, 24, 203–218. Lindeman, M., & Sirelius, M. (2001). Food choice ideologies: the modern manifestations of normative and humanist views of the world. Appetite, 37, 175–184. Marquis, M. (2005). Exploring convenience orientation as a food motivation for college students living in residence halls. International Journal of Consumer Studies, 29, 55– 63. Martins, Y., & Pliner, P. (1998). The development of the food motivation scale. Appetite, 30, 94. Martins, Y., & Pliner, P. (2005). Human food choices: an examination of the factors underlying acceptance/rejection of novel and familiar animal and nonanimal foods. Appetite, 45, 214–224. Nisbett, R. E. (1968). Taste, deprivation, and weight determinants of eating behavior. 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Capaldi & T. L. Powley (Eds.), Taste, experience, and feeding (pp. 210–226). Washington, DC: American Psychological Association. Prescott, J., Young, O., O’Neill, L., Yau, N. J. N., & Stevens, R. (2002). Cross-cultural differences in motives for food choice: a comparison of consumers from Japan, Taiwan. Malaysia and New Zealand. Food Quality & Preference, 13, 489–495. Rappoport, L. H., Peters, G. R., Downey, R. G., McCann, T., & Huff-Corzine, L. (1993). Gender and age differences in food cognition. Appetite, 20, 33–52. Roininen, K., La¨hteenma¨ki, L., & Tuorila, H. (1999). Quantification of consumer attitudes to health and hedonic characteristics of foods. Appetite, 33, 71–88. Roininen, K., Tuorila, H., Zandstra, E. H., De Graaf, C., Vehkalahti, K., Stubenitsky, K., et al. (2001). Differences in health and taste attitudes and reported behavior among Finnish, Dutch and British consumers: a cross-cultural validation of health and taste attitude scales (HTAS). Appetite, 37, 33–45. Rozin, P., & Zellner, D. (1985). The role of Pavlovian conditioning in the acquisition of food likes and dislikes. Annals of the New York Academy of Sciences, 443, 189–202. Scheibehenne, B., Miesler, L., & Todd, P. M. (2007). Fast and frugal food choices. Uncovering individual decision heuristics. Appetite, 49, 578–589. SPSS Inc.. (2009). SPSS 14. Statistical algorithms. Chicago, IL: CONJOINT. Stafleu, A., de Graaf, C., van Staveren, W. A., & Schroots, J. F. (1991). A review of selected studies assessing social-psychological determinants of fat and cholesterol intake. Food Quality and Preference, 3, 183–200. Steptoe, A., Pollard, T. M., & Wardle, J. (1995). Development of a measure of the motives underlying the selection of food: the Food Choice Questionnaire. Appetite, 25, 267– 284. Thurstone, L. (1927). A law of comparative judgment. Psychological Review, 34, 273– 286. Wardle, A., Haase, A. M., Steptoe, A., Nillapun, M., Jonwutiwes, K., & Bellisie, F. (2004). 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Contents lists available at ScienceDirect
Appetite journal homepage: www.elsevier.com/locate/appet
Short communication
Hunger induced changes in food choice. When beggars cannot be choosers even if they are allowed to choose Atilla Hoefling *, Fritz Strack Department of Psychology, University of Wu¨rzburg, Ro¨ntgenring 10, D-97070 Wu¨rzburg, Germany
A R T I C L E I N F O
A B S T R A C T
Article history: Received 16 September 2009 Received in revised form 23 February 2010 Accepted 25 February 2010
The present work was to examine the influence of food deprivation on food choice. For this purpose hungry versus satiated subjects were presented with a series of choices between two snacks in a complete block design of pairwise comparisons. Snacks systematically varied with respect to subjects’ idiosyncratic taste preferences (preferred versus un-preferred snack), portion size (large portion versus very small portion), and availability in terms of time (immediately available versus available only after a substantial time delay). Food choices were analyzed with a conjoint analysis which corroborated the assumption that food deprivation decreases the relative importance of taste preference and increases the importance of immediate availability of food. ß 2010 Elsevier Ltd. All rights reserved.
Keywords: Food deprivation Food choice Food preferences Taste preferences Conjoint analysis
Prior research on human food choice revealed that good flavor and sensory appeal seem to be of major importance when deciding which foods to pick for consumption, and which foods to reject (e.g., Eertmans, Baeyens, & Van den Bergh, 2001; Martins & Pliner, 1998, 2005; Rozin & Zellner, 1985; Scheibehenne, Miesler, & Todd, 2007; Stafleu, de Graaf, van Staveren, & Schroots, 1991; Steptoe, Pollard, & Wardle, 1995). In addition, factors like health and weight concerns, ethical considerations, convenience, price, familiarity, and anticipated emotional effects were found to be important decision criteria for human food choices, too (e.g., Candel, 2001; Connors, Bisogni, Sobal, & Devine, 2001; Eertmans, Victoir, Vansant, & Van den Bergh, 2005; Green, Draper, & Dowler, 2003; Marquis, 2005; Martins & Pliner, 1998; Roininen, La¨hteenma¨ki, & Tuorila, 1999; Roininen et al., 2001; Rozin & Zellner, 1985; Scheibehenne et al., 2007; Stafleu et al., 1991; Steptoe et al., 1995; Zandstra, de Graaf, & Van Staveren, 2001). Noteworthy, past research also yielded that there exist stable interindividual differences in the importance of these factors (e.g., Glanz, Basil, Maibach, Goldberg, & Snyder, 1998; Lindeman & Sirelius, 2001; Oakes & Slotterback, 2001; Pilgrim, 1957; Prescott, Young, O’Neill, Yau, & Stevens, 2002; Rappoport, Peters, Downey, McCann, & Huff-Corzine, 1993; Wardle et al., 2004). The influence of food deprivation on food choice It was acknowledged elsewhere that the importance of a given factor might also vary as a function of contextual cues. In
* Corresponding author. E-mail address: hoefl[email protected] (A. Hoefling). 0195-6663/$ – see front matter ß 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.appet.2010.02.016
particular, it was speculated that an organism’s physiological need state might provide a contextual cue that has the potential to increase the relative importance of nutritional value (compared to other food attributes like price) in the realm of food choice (Scheibehenne et al., 2007). This reasoning is in line with the commonsensical assumption that the eating behavior of hungry organisms should be determined by physiological demands rather than by psychological influences (Herman & Polivy, 1984; Jacobs & Sharma, 1969; Nisbett, 1972), which is also reflected in the proverb ‘‘Beggars cannot be Choosers’’. To put it in simple terms, immediate satiation should matter more for the food deprived organism than exquisite flavor or gourmet-like presentation. Despite having face validity the above mentioned assumptions are anecdotal and were never put under systematic experimental investigation to the present day. Some relevant studies yielded that food deprived subjects were more willing than satiated subjects to consume even unpalatable (bitter) foods when nothing else was available, thereby giving at best a first hint that the importance of certain food attributes (e.g., good flavor) may be moderated by physiological need states (e.g., Bellisle, Lucas, Amrani, & Le Magnen, 1984; Desor, Maller, & Green, 1977; Hill, 1974; Hill & McCutcheon, 1975; Nisbett, 1968; but see also Kauffman, Herman, & Polivy, 1995 or Pliner, Herman, & Polivy, 1990 for conflicting results and for an integration of these incompatible findings). Noteworthy, the influence of food deprivation on the relative importance of food attributes like palatability or nutrient content was never assessed directly before. To bridge this gap, a computerized food choice task was conducted, and relative weights of three critical food attributes were computed in a conjoint analysis. In short, different snack options (two at a time) were presented on a
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computer screen that varied with respect to subjects’ idiosyncratic taste preferences (preferred versus un-preferred snack), portion size (very small portion versus large portion), and availability in terms of time (immediately available versus available only after a delay of 90 min). Subjects were asked to choose their preferred snack option across a number of different trials and the relative importance for each snack attribute was computed separately for hungry and satiated subjects on the basis of these choices. Hypotheses. It is assumed that the utility derived from good flavor decreases for the starving organism, whereas the utility derived from immediate availability and large portion size increases. As a result, the relative part worth (or weighting) of idiosyncratic taste preference in a conjoint analysis should be significantly smaller for food deprived participants than for satiated participants, whereas the importance of both, (large) portion size and (short) waiting time should be larger. Furthermore, it was expected that the utility structure within each experimental group should be affected by food deprivation, too. That is, idiosyncratic taste preference (compared to portion size and waiting time) should be more important for satiated subjects, but less important for food deprived subjects.
lunch immediately before the experiment (which was said to heighten their blood glucose level). Satiated participants were free to eat what they want, but were instructed to have at least a warm main course, a desert and a non-alcoholic drink. Experimental sessions started at noon or 1:30 p.m., and participants (groups up to three persons who were tested at a separate table) signed a consent form and reported their current mood before rank ordering 8 different, customary snacks according to their momentary taste preference. Then, subjects completed the aforementioned measure of concentration followed by the computerized food choice task (paired comparisons) and a set of demographic questions including subjective feelings of hunger serving as a manipulation check. Finally, subjects were probed for suspicion and debriefed Mood assessment In order to ensure that a priori mood differences are not responsible for any of the reported findings (food deprived subjects might be in a worse mood due to their state of deprivation), subjects were asked how strongly they agree with the statement ‘‘I am in a good mood right now’’ on a scale ranging from 1 (totally disagree) to 6 (totally agree) at the beginning of the session.
Methods Participants and design Fifty-nine undergraduate psychology students (43 female) at the University of Wu¨rzburg (Germany) took part in an experiment that was introduced as consisting of several studies including one experiment on the effects of blood glucose levels on concentration (concentration test) and one experiment on consumer psychology. In fact, the only purpose of the concentration test (for details see Brickenkamp, 1962; Oswald, Hagen, & Brickenkamp, 1997) was to cover the manipulation of need state and to minimize demand effects that might arise when subjects form an explicit link between their need state and the food choice task. Hence it will not be reported any further. All subjects received course credits for participation. Aside from need state, three critical attributes of experimental foods were manipulated within a food choice task, resulting in a 2 (need state: deprived versus satiated) 2 (idiosyncratic taste preference: preferred snack versus non-preferred snack) 2 (portion size: very small portion versus large portion) 2 2 (availability: immediately available versus available only after 90 min delay) mixed factorial design with need state being manipulated between participants. To minimize the role of health and weight concerns (that were not of interest in the present study) only normal eating, normal weight subjects were included. That is, persons being on a diet during the period of data collection or having food-relevant allergies were not invited for participation, and subjects with a Body Mass Index (BMI) below 17.5 (n = 1), or above 25 (n = 5) were excluded from the analyses. Vegetarians were included because no food stimuli were presented that included meat. Two more subjects had to be excluded because of computer errors. The resulting sample consisted of 14 men and 37 women, aged between 18 and 41 years (M = 21.64, SD = 3.76). Experimental groups did not differ in the percentage of women (hungry: 74.1% versus satiated: 70.8%), x2 (1; N = 51) < 1, BMI (Mhungry = 21.46, SD = 2.03 versus Msatiated = 21.35, SD = 1.92), t(49) < 1, or age (Mhungry = 21.30, SD = 2.54 versus Msatiated = 22.08, SD = 4.75), t(49) < 1. Procedure and materials Procedure Participants were either asked to refrain from eating for 15 h (which was said to lower their blood glucose level), or to have
Rank ordering procedure To vary taste preference on an idiosyncratic level (see following paragraph) participants rank ordered 8 different, customary snacks according to their momentary preference from 1 (most preferred snack) to 8 (least preferred snack). The snacks were potato chips, salty peanuts, M&M’s chocolate peanuts, gummy bears, milk chocolate, salty crackers, cheese sticks, and butter muffins. Food choice task (paired comparisons) Paired comparisons were introduced as a study on consumer psychology consisting of several food choices. In each trial, subjects were instructed to choose between two snack options depicted on ‘‘randomly chosen photographs’’ on a computer screen. The position of each option on the screen (right versus left side) was determined randomly in each trial. In fact, each subject processed a specific computer file that included only photographs of the two snacks ranked on position 2 (preferred snack) and 6 (un-preferred snack) in the rank ordering procedure (manipulation of idiosyncratic taste preference). Extreme ranks were not selected in order to ensure that all critical features are related to each other in a compensatory manner, and that taste preference would not act as a ‘‘K.O.-criterion’’ in the conjoint analysis (see Backhaus, Erichson, Plinke, & Weber, 2003). Portion size was manipulated by photographing each snack on a plate under standardized conditions, both, in a small and large portion size version. The actual amount of food used for each version was determined in such a way that subjects from a separate pretest sample expected only the large portion of each snack to be filling, but not the small portion. Availability in terms of time was manipulated by giving written information on top of each photograph (immediately available versus available in 90 min). Systematically combining these three features of twofold gradation resulted in a total number of 8 different snack options that served as objects in a complete block design of 28 paired comparisons (Thurstone, 1927). Importantly, a snack option (or object, respectively) is defined as a photograph plus written information. Since all factors were discrete and of twofold gradation, the utility of the second parameter value represents the mere reciprocal of the first parameter value for each factor and was not relevant for further analysis (see SPSS, 2009). Thus, utility scores (uj) were only computed for the following specific food attributes (j): getting a favored snack, getting a large portion, and getting a snack immediately. In particular, utility scores were
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estimated for each subject separately by rank ordering all snack options (objects) according to the number of trials in which they had been preferred, and applying an Ordinary Least Squares regression algorithm on these ordinal data. That is, the part worth for each attribute (j) was computed as the difference between its mean rank and the unweighted mean rank of the respective factor. Afterwards, scores of relative importance (impj) were calculated P for each attribute (j) as 100 (uj/ uj) and aggregated for hungry and satiated subjects separately. Noteworthy, scores of relative importance represent percent-values that can be interpreted in an absolute manner. Hunger ratings Subjective feelings of hunger were reported on a scale ranging from 1 (not hungry at all) to 7 (very hungry) after the food choice task and served as a manipulation check. Albeit the exposure to food stimuli might have influenced subsequent hunger ratings, this positioning seemed most appropriate to prevent subjects from explicitly linking the hunger manipulation to the food choice task.
Fig. 1. Relative importance of idiosyncratic taste preference, (large) portion size, and (short) waiting time as a function of need state. Error bars indicate standard errors of the means.
Hunger ratings were analyzed with a simple t-test. As expected, food deprived participants (M = 5.56, SD = 1.50) reported stronger feelings of hunger than satiated participants (M = 2.54, SD = 1.82), t(49) = 6.77, p < .001, d = 1.81.
important than portion size or waiting time amongst hungry subjects. An inspection of Fig. 1 reveals that (for satiated subjects) idiosyncratic taste preference was indeed more important than (short) waiting time, t(23) = 3.73, p = .001, d = 1.32, or (large) portion size, t(23) = 2.02, p = .056, d = .75. Amongst hungry subjects this pattern disappeared but did not reverse. That is, taste preference was only slightly less important than portion size, t(23) = 2.02, p = .15, but not less important than waiting time, t < 1.
Preliminary analyses
Discussion
Self-reports of mood were analyzed with a simple t-test that yielded no a priori differences in mood between satiated subjects (M = 4.00, SD = 1.22) and food deprived subjects (M = 3.74, SD = 1.29), t(49) < 1. Consequently, this variable was discarded.
The results of the present study strongly corroborate the assumption that food deprivation decreases the importance of idiosyncratic taste preferences for the benefit of immediate availability in the realm of food choice. That is, compared to satiated participants, food deprived participants did not predominantly select a preferred snack but were more intent on getting anything to eat immediately. In sharp contrast, idiosyncratic taste preference was clearly the most important selection criterion amongst satiated subjects (see also Rozin & Zellner, 1985; Scheibehenne et al., 2007; Stafleu et al., 1991), who predominantly insisted on getting their favored snack and were willing to accept small portion sizes and long waiting times for it. The finding that all food features were nearly equally important for hungry subjects make clear that these priorities change, but do not completely reverse under conditions of starvation. That is, taste preferences become less important, but not insignificant in a state of food deprivation. One anonymous reviewer noted that the observed data pattern might also indicate that food choices may be based on different underlying mechanisms amongst food deprived and satiated subjects. That is, maybe hungry subjects make more complex and weighted decisions whereas satiated subjects base their choices just on taste as the most important criterion. It is true that both complex weighted additive mechanisms (e.g., Eertmans et al., 2005; Glanz et al., 1998; Rappoport et al., 1993; Scheibehenne et al., 2007), and simple heuristics (e.g., Connors et al., 2001; Scheibehenne et al., 2007) were put forward as adequate explanatory frameworks in the realm of food choice. However, given that it was not investigated to the present day if food deprivation has an impact on these procedural factors a pronouncement on this issue would go beyond the scope of the present paper and remains an issue for further research. Noteworthy, food deprived subjects’ willingness to choose unpreferred but immediately available foods in the present study is in line with previous studies on food intake yielding greater
Results Manipulation check
Relative importance of food attributes The relative importance of food attributes was analyzed with a 2 (need state: deprived versus satiated) 3 (food attribute: idiosyncratic taste preference versus portion size versus waiting time) mixed model ANOVA with need state being manipulated between subjects. The analysis revealed a significant main effect of food attribute, multivariate F(2,48) = 4.41, p = .017, d = .44, that was qualified by a significant need state food attribute interaction, multivariate F(2,48) = 6.21, p = .004, d = .52 (see Fig. 1). Follow-up t-tests were conducted to specify this interaction. In line with the central predictions it was found that the relative importance of idiosyncratic taste preference was greater for satiated subjects than for food deprived subjects,1 t(39.58) = 3.26, p = .002, d = .93. This indicates that it was more important for satiated subjects to get their favored snack than for food deprived subjects. In contrast, the relative importance of (short) waiting time was greater for food deprived subjects than for satiated subjects, t(49) = 2.52, p = .015, d = .71. The importance of (large) portion size however did not differ significantly between groups, t(49) = 1.27, p = .21. A second issue pertains to the trade-off between the three attributes within each experimental group. For this purpose, t-tests for dependent measures were conducted for food deprived and satiated subjects separately. To repeat, it was hypothesized that idiosyncratic taste preferences should be the most important selection criterion for satiated subjects, but should be less 1 Due to inhomogeneity of variances, a correction of degrees of freedom (df) was used.
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consumption of un-preferred foods amongst food deprived subjects (e.g., Bellisle et al., 1984; Desor et al., 1977; Hill, 1974; Hill & McCutcheon, 1975; Kauffman et al., 1995; Nisbett, 1968; Nisbett, Hanson, Harris, & Stair, 1973). However, while indicating that food deprived subjects will readily accept even un-preferred foods if nothing else is available, these latter studies are quite uninformative about the underlying mental mechanisms at the same time. By pitting taste preferences, portion size and availability in terms of time against each other in a conjoint analysis it was possible to determine more precisely why food deprived subjects do accept un-preferred foods more readily than satiated subjects. In essence, this might be the case because taste preferences loose their importance when being in a state of homeostatic dysregulation. With respect to the mental mechanisms underlying food deprived participants’ greater acceptance of unpalatable foods, the present study also relates to prior work on food deprivation and food related disgust. Hoefling et al. (2009) found for example that food deprived subjects exhibited weaker facial disgust reactions than satiated subjects when being confronted with disgusting foods despite evaluating them equally negative on an explicit level of information processing. It was concluded from this finding that food deprived participants’ greater consumption of unpalatable foods might also be due to an involuntary shift in their immediate affective reactions towards these foods. Although the un-preferred snacks in the present study were probably not rejected to the same extent as disgusting foods, the presented results are nevertheless informative about another possible mental mechanism underlying food deprived subjects’ greater acceptance and consumption of unpalatable foods, namely the change in the relative importance of mere palatability versus more functional food features. Based on the present findings it might also be interesting to examine if food deprivation does affect the importance of other factors (e.g., price, healthiness) too, and to compare restrained eaters/ eating disordered subjects’ food choices to those of normal eating subjects. Since determinants of food choices might be quite different in these samples, future studies might focus on the trade-off between the need for immediate satiation and health concerns under conditions of starvation and check whether restrained and normal eating subjects do value critical aspects of food to the same extent. References Backhaus, K., Erichson, B., Plinke, W., & Weber, R. (2003). Multivariate Analysemethoden. Eine anwendungsorientierte Einfu¨hrung. Berlin: Springer. Bellisle, F., Lucas, F., Amrani, R., & Le Magnen, J. (1984). Deprivation, palatability, and the micro-structure of meals in human subjects. Appetite, 5, 85–94. Brickenkamp, R. (1962). Aufmerksamkeits-Belastungs-Test (Test d2). Go¨ttingen: Hogrefe. Candel, M.J.J.M.. (2001). Consumers’ convenience orientation towards meal preparation: conceptualization and measurement. Appetite, 36, 15–28. Connors, M., Bisogni, C. A., Sobal, J., & Devine, C. M. (2001). Managing values in personal food systems. Appetite, 36, 189–200. Desor, J. A., Maller, O., & Green, L. S. (1977). Preference for sweet in humans: infants, children, and adults. In J. M. Weiffenbach (Ed.), Taste and development: the genesis of sweet preference (pp. 161–172). Washington: Government Printing Office. Eertmans, A., Baeyens, F., & Van den Bergh, O. (2001). Food likes and their relative importance in human eating behavior: review and preliminary suggestions for health promotion. Health Education Research, 16, 443–456. Eertmans, A., Victoir, A., Vansant, G., & Van den Bergh, O. (2005). Food-related personality traits, food choice motives and food intake: mediator and moderator relationships. Food Quality and Preferences, 16, 714–726. Glanz, K., Basil, M., Maibach, E., Goldberg, J., & Snyder, D. (1998). Why Americans eat what they do: taste, nutrition, cost, convenience, and weight control concerns as
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