A behavioral economics analysis of food choice in humans

The challenge of identifying behavioral alternatives to food: clinic and field studies

BACKGROUND

One of the basic principles of behavioral economics interventions is identification of alternative behaviors to compete with the reinforcing value of a highly rewarding commodity.

PURPOSE

Two experiments that attempt to increase alternatives to eating in obese youth are presented.

METHODS

A randomized, controlled trial was used in Study 1 to compare a comprehensive family-based behavioral treatment program or an experimental treatment that incorporated reinforcing children for engaging in alternative behaviors to eating for 41 overweight 8- to 12-year-old children. Study 2 used a within-subject design with baseline, enriched environment and a second baseline phase to determine the influence of providing activities that compete with eating for 13 overweight 8- to 12-year-old children. Measurements included body mass index (BMI) change, alternatives to eating, eating, and physical activity.

RESULTS

In Study 1 both treatments were associated with significant (p < .05) and maintained reductions in z-BMI over the 24 months of observation. The experimental group showed a significantly (p < .05) greater increase in alternatives to eating, and both groups showed significant (p < .05) increases in physical activity. In Study 2 alternative behaviors to eating were increased by almost 1 hr/day (p < .001) but were not associated with significant changes in energy intake or physical activity.

CONCLUSION

These results suggest that using the methods studied, increasing behaviors that could compete with eating did not influence relative weight in a clinical outcome study or energy intake in a controlled field study.

Food reinforcement

The reinforcing value of food, measured by how hard someone is willing to work to obtain food, is influenced by food palatability, food deprivation and food variety, and may be a more powerful determinant of food intake than hedonics or liking. The reinforcing value of food is mediated in part by dopaminergic activity. Genotypes that influence dopamine transport and the density of dopamine D2 receptors interact with food reinforcement to influence eating behavior, and D2 receptor genotypes may influence food reinforcement and weight gain after smoking cessation. Inhibition of dopamine transport increases brain dopamine concentrations, which may influence weight gain after smoking cessation and can reduce energy intake in obese adults.

Validation of a questionnaire measure of the relative reinforcing value of food

The traditional method of measuring the relative reinforcing value of food provides subjects a choice of food and non-food alternatives, and defines the relative reinforcing value of food based on the allocation of responses for the two alternatives as the schedules of reinforcement for the alternatives change. Greater allocation of responses for one alternative versus another reflects the relative reinforcing value of the alternatives. This method was designed for laboratory use, but methods are needed to extend measurement of reinforcing value to applied research environments. Two experiments were conducted to assess the validity of a questionnaire measure of the relative reinforcing value of food in normal weight university samples. Study 1 (n=39) assessed the relationship between the relative reinforcing value of snack food versus fruits and vegetables (condition 1) or enjoyable sedentary behaviors (condition 2) as measured by the questionnaire and standardized computerized concurrent schedules criterion. A significant relationship (Pearson r=0.49, p<0.01; Guttman's MU2=0.69) across the two conditions between the two methods of measuring food reinforcement was observed. Experiment 2 (n=10) utilized a within-subject counterbalanced design to manipulate food deprivation and hunger levels to determine if food deprivation increased the reinforcing value of snack food as measured by the questionnaire to provide an index of validity of the questionnaire. Results showed that food deprivation increased the relative reinforcing value of snack food. Results from both studies suggest that the questionnaire has good validity, and may represent an efficient and reliable method of assessing the relative reinforcing value of food.

Development and modification of child food preferences and eating patterns: behavior genetics strategies

Behavioral genetics (BG) designs can offer useful strategies for studying the development of child food preferences and eating patterns. This review summarizes BG designs that tested familial influences on child eating behavior and implicated both genetic and home environmental factors. A range of BG strategies, including family and pseudo-family designs, classic twins designs, discordant sibling designs, cotwin control designs, and high-risk designs, have provided information on child development that could not have been obtained from the analysis of singletons. BG designs can provide can powerful tools for testing environmental theories of child nutrition and, potentially, for better understanding between-child variability in response to dietary interventions for overweight. The term BG may misleadingly imply only the classic twin design or just heritability estimation; BG strategies can be adapted creatively to address a range of questions concerning the development of child appetite and eating regulation.

Craving and startle modification during in vivo exposure to food cues

RATIONALE AND OBJECTIVES

Food craving and reactivity to food cues are related to food intake. Research has shown that both startle magnitude and prepulse inhibition of startle may be useful indices of cue reactivity and drug craving. The goal of this study was to assess the utility of these paradigms for the study of food craving in food-deprived participants.

METHODS

Twenty-nine non-smoking, food-deprived undergraduate participants were exposed to a counterbalanced series of food, cigarette, and neutral cues. During each 4.5-min cue, nine startle probes (102-dB white noise) were presented, and a prepulse (20-ms noise 8 dB above background) preceded 2/3 of the probes by 60 or 120 ms. Subjects were divided into those high and low in food-craving on the basis of subjective craving to food cues. Responses to food cues were compared to smoking cues to control for attention and arousal.

RESULTS

Both probe-alone startle magnitude and percent prepulse inhibition were significantly reduced during the food cue compared to the smoking cue among high food cravers, but not low food cravers. These processes seemed to be independent, as cue-induced changes in prepulse inhibition were uncorrelated with cue effects on probe-alone startle magnitude.

CONCLUSIONS

Both probe-alone startle magnitude and prepulse inhibition are sensitive to cue-induced craving for food, but appear to assess separate processes. Startle methodologies may prove useful in understanding basic processes that regulate food intake.

Body Mass Index and Alcohol Use

BACKGROUND

Obesity, inactivity and being overweight are leading causes of morbidity and mortality in the United States. The relationship between eating, overeating, and addiction have been discussed, debated and more recently investigated. We have hypothesized that drugs of abuse compete with food for brain reward sites. Overeating and obesity may act as protective factors reducing drug reward and addiction.

METHODS

In the first part of this study, 374 charts of all active weight management patients in a 12-month period were examined. Demographic information, laboratory testing, psychiatric diagnostic interview, alcohol and drug history were reviewed. A detailed alcohol use, abuse, dependence history was present in 298 charts as part of the pre-bariatric evaluation. The relationship between BMI and alcohol use among female patients (n = 298) was then analyzed.

RESULTS

We found a significant (p <.05) inverse relationship between BMI and alcohol consumption. The more obese the patient was, the less alcohol they consumed. The percentage of women who consumed alcohol in the past year decreased as BMI level increased. These results confirmed our surgeons' perception that it is rare to find a morbidly obese patient excluded for bariatric surgery because of excessive alcohol consumption.

CONCLUSIONS

Obese patients have lower rates of alcohol use than found in the general population of women. As BMI increases, lower rates of alcohol consumption are found. Overeating may compete with alcohol for brain reward sites, making alcohol ingestion less reinforcing.

Relation between food reinforcement and dopamine genotypes and its effect on food intake in smokers

BACKGROUND

Food reinforcement and dopaminergic activity may influence food consumption, but research on whether they interact has not been performed.

OBJECTIVE

We assessed the effects of food reinforcement and the interaction of food reinforcement with the dopamine transporter (SLC6A3) genotype and the dopamine D(2) receptor (DRD(2)) genotype on energy consumption.

DESIGN

We studied food-consumption and reinforcing-value-of-food tasks in 88 smokers of European ancestry before they enrolled in smoking-cessation treatment. In the food-consumption task, subjects tasted and consumed 8 snack foods ad libitum. The reinforcing-value-of-food task assessed how hard subjects would work for food.

RESULTS

Significant interactions between dopamine genotypes and food reinforcement were observed. Subjects high in food reinforcement who lacked an SLC6A3*9 allele consumed significantly more calories (>150 kcal; P = 0.015) than did subjects low in food reinforcement or those high in food reinforcement who carried at least one SLC6A3*9 allele. Similarly, subjects high in food reinforcement who carried at least one DRD(2)*A1 allele consumed >130 kcal more (P = 0.021) than did subjects low in food reinforcement or those high in food reinforcement who lacked a DRD(2)*A1 allele. There was also a main effect of food reinforcement on energy intake (P = 0.005), with subjects high in food reinforcement consuming 104 kcal (or 30%) more than did subjects low in food reinforcement.

CONCLUSIONS

Food reinforcement has a significant effect on energy intake, and the effect is moderated by the dopamine loci SLC6A3 and DRD(2).

Habituation of salivation and motivated responding for food in children

Repeated presentation of food cues results in habituation in adults, as demonstrated by a decrement in salivary responding that is reversed by presenting a new food cue in adults. Food reinforced behavior in animals shows the same pattern of responding, with a decrease in responding to obtain the food, followed by a recovery of responding when a new food is presented. The present study assessed whether children would show the same pattern of a decrement of food reinforced responding followed by recovery of responding when a new food is presented for both salivation and food reinforcement tasks. Subjects were assigned to one of two groups that differed in the trial that the new food stimulus was presented to ensure recovery was specific to the introduction of the new food stimulus. In the salivation task, subjects were provided repeated olfactory presentations of a cheeseburger with apple pie as the new food stimulus, while in the food reinforcement task subjects worked for the opportunity to consume a cheeseburger, followed by the opportunity to work for consumption of apple pie. Subjects in both groups showed a decrement in salivary and food reinforced responding to repeated food cues followed by immediate recovery of responding on the trial when a new food was presented. Subjects increased their energy intake by over 30% in the food reinforcement task when a new food was presented. These results are consistent with the general process theory of motivation that suggests that changes in food reinforced responding may be due in part to habituation.

Physical activity and sedentary behavior: a population-based study of barriers, enjoyment, and preference

The associations of physical activity and sedentary behavior with barriers, enjoyment, and preferences were examined in a population-based mail survey of 1,332 adults. Respondents reporting high enjoyment and preference for physical activity were more likely to report high levels of activity. Those reporting cost, the weather, and personal barriers to physical activity were less likely to be physically active. Preference for sedentary behavior was associated with the decreased likelihood of being physically active, and the weather a barrier to physical activity was associated with the increased likelihood of sedentary behavior. These constructs can be used to examine individual and environmental influences on physical activity and sedentary behavior in specific populations and could inform the development of targeted interventions.

Desire to eat high- and low-fat foods following a low-fat dietary intervention

OBJECTIVE

This study examined changes in desires to eat high-fat and low-fat foods across an obesity treatment program. The hypotheses under examination were (1) preferences for low-fat foods would increase across time and (2) preferences for high-fat foods would decrease across time.

DESIGN

Single-group, prospective examination of desires to eat 48 foods, categorized according to fat content, before and after the 16-week treatment program.

SETTING

University clinic, Memphis, Tennessee.

PARTICIPANTS

118 obese (mean weight = 194.4 lbs) women (mean age = 45.24 years) participating in an obesity treatment program.

INTERVENTION

A 16-week cognitive-behavioral program for obesity.

VARIABLES MEASURED

Desires to eat 48 foods varying in fat content and whether or not participants actually ate these foods.

ANALYSIS

Analysis of variance, multiple regression, and paired t tests.

RESULTS

The results indicate that during the program, preferences for low-fat foods increased, whereas preferences for high-fat foods decreased. These changes mirrored the changes in consumption of both low-fat and high-fat foods.

CONCLUSIONS AND IMPLICATIONS

Within a behavioral economic perspective, the reinforcement value of low-fat foods may increase following a low-fat dietary intervention, whereas the reinforcing properties of high-fat foods may decline. This is desirable as low-fat foods hold many advantages over high-fat foods in terms of weight maintenance.

Effects of deprivation on hedonics and reinforcing value of food

Eating is influenced by both the hedonic preferences and reinforcing value of food. Incentive salience theory predicts these are separate influences. This study tested whether hedonics reliably change as a function of increasing the reinforcing value of food by deprivation in 17 non-obese, non-dietary restrained females. Baseline measures of hedonics for pleasant (chocolate milk), unpleasant (lemon juice) and neutral (water) tastes were determined under deprived conditions. Participants were then randomly assigned to fed or maintained in deprived conditions, and after food consumption, a second determination of hedonics was obtained, followed by assessing the reinforcing value of food. Hedonics was measured by subjective ratings and behavioral observations in a taste reactivity paradigm. Results showed food was more reinforcing for the deprived than the fed group, but no influences of group were observed for the subjective or objective hedonic measures. These results suggest that hedonics and the reinforcing value of food are separate processes in humans, and they may independently influence eating behavior.

The relative-reinforcing value of food under differing levels of food deprivation and restriction

Food deprivation and restriction both increase food consumption. Food deprivation also increases the reinforcing value of food, but it is unknown if food restriction alone or combined with deprivation increases the reinforcing value of food. Forty, normal-weight, college-aged, unrestrained females were randomized to one of four conditions that crossed food deprivation (Dep) and restriction (Res): Dep/Res, Dep/No Res, No Dep/Res, No Dep/No Res. All participants arrived at least 13h food-deprived, and non-deprived participants consumed at least 365cal from a drink during the session. Restriction was manipulated by placing snack food in front of participants, without access for 15min during the session, or having no snack food placed in front of participants. Following the experimental manipulations, participants completed a computer choice task to determine the reinforcing value of food. Repeated measures analysis of variance found a significant main effect of deprivation (p<0.05) and trials (p<0.001) for food points earned. Deprived participants found food to be more reinforcing, and the reinforcing value of food decreased over time. This suggests that while short-term food deprivation increases the relative-reinforcing value of food, short-term food restriction has no effect on the relative-reinforcing value of food in unrestrained eaters.

Temporal discounting: basic research and the analysis of socially important behavior

Recent basic research on human temporal discounting is reviewed to illustrate procedures, summarize key findings, and draw parallels with both nonhuman animal research and conceptual writings on self-control. Lessons derived from this research are then applied to the challenge of analyzing socially important behaviors such as drug abuse, eating and exercise, and impulsiveness associated with attention deficit hyperactivity disorder. Attending to the broader temporal context in which behavior occurs may aid in the analysis of socially important behavior. Applying this perspective to the study of behavior in natural environments also highlights the importance of combining methodological flexibility with conceptual rigor to promote the extension of applied behavior analysis to a broader array of socially important behaviors.

A behavioral economic analysis of fat appetite in rats

A behavioral economic analysis of rats' consumption of various fat and sweet solutions was conducted in order to assess whether rats' fat appetite is readily modifiable. According to economic demand theory, changes in the price of a reinforcer will produce substantial changes in its consumption under conditions in which a substitutable reinforcer is available. Results from income-compensated price changes revealed that sucrose, mineral oil and saccharin solutions substituted for a corn oil solution: increases in the price of the corn oil led to large decreases in its consumption and sizable increases in consumption of these alternatives. On the other hand, plain water did not substitute for the corn oil solution: increasing the price of the corn oil did not result in nearly as marked a change in its consumption nor in consumption of the water. Neither the strength of preference for the corn oil under baseline conditions nor the caloric content of the alternative solution predicted whether the alternative reinforcer substituted for the corn oil. Rather, palatability appeared to be a dimension along which substitution was based. These results suggest that fat appetite is modified when palatable alternatives are available, independent of how strongly the fat is preferred.

Effect of the number of high-fat and low-fat cues on food choice

This study examined the effects on food choice of increasing the number of healthy items available (fruit) and decreasing the number of unhealthy items available (candy bars). A similar choice, involving nonfood items, was also examined. Two hundred eighty-nine men and women were randomly assigned to 1 of 4 experimental groups: (a) control group, (b) increased number of fruits, (c) decreased number of candy bars, and (d) combination. Between 30% and 40% of participants chose fruit regardless of the amount of fruit and candy presented: there was no effect of increasing fruit or decreasing candy bars. However, restrained participants and current dieters were more likely to choose fruit. In contrast, both stimulus control techniques were effective in increasing the percentage of participants choosing a nonfood item. These results suggest that stimulus control may not be sufficient to modify food choice: other powerful factors affect eating behavior, and these must be considered.

Caffeine withdrawal symptoms and self-administration following caffeine deprivation

This study examined the effects of complete or partial caffeine deprivation on withdrawal symptomatology and self-administration of coffee in caffeine-dependent coffee drinkers. Nine habitual coffee drinkers abstained from dietary sources of caffeine for 33.5 h. Caffeine deprivation was manipulated by administering capsules containing 0%, 50%, or 100% of each subject's daily caffeine intake (complete, partial, and no deprivation conditions). Caffeine withdrawal symptomatology was measured using self-report questionnaires. Caffeine self-administration was measured using: i) the amount of coffee subjects earned on a series of concurrent random-ratio schedules that yielded coffee and money reinforcers; ii) the amount of earned coffee they consumed. Saliva samples revealed that subjects complied with the caffeine abstinence instructions. Caffeine withdrawal symptoms occurred reliably following complete caffeine deprivation, though not in the partial deprivation condition. Caffeine self-administration was not related to deprivation condition. We conclude that caffeine withdrawal symptomatology is not necessarily associated with increased caffeine consumption.

Gender, dietary restraint, and smoking's influence on hunger and the reinforcing value of food

Smoking may enhance satiety following meal consumption, thereby reducing subsequent eating (i.e., between-meal snacks), especially in women high in dietary restraint. Female smokers (n = 20, 10 high and 10 low restraint) and male smokers (n = 10) participated in two sessions, involving overnight abstinence from food and smoking (smoking abstinence day) or from food only (smoking day), in a within-subjects design. The reinforcing value of food was determined by the number of responses made to obtain food reinforcers (100-kcal snack portions) vs. money using a concurrent schedules computer task. Subjects were given a small caloric load on each day followed by access to food vs. money. On the smoking day, subjects were allowed to smoke every 30 min during the session as well as ad lib before the session. Self-reported hunger was also assessed upon arrival (after fasting) and following the caloric load during each session. Results indicated no effect of smoking on initial hunger rating, after fasting, but hunger ratings following the caloric load declined significantly more during smoking vs. abstinence days for all subjects, consistent with an enhancement of postmeal satiety due to smoking. There was no overall main effect of smoking on food-reinforced responding. However, responding for food was significantly less during the smoking vs. abstinence days for high-restraint females only and not for low-restraint females or for males. These findings indicate that smoking's acute influence on reducing food intake does not reflect a broad gender difference but may be specific to dietary restraint.

Effects of reinforcing increases in active behavior versus decreases in sedentary behavior for obese children

This experiment tested the effects of reinforcing obese children lo be more active or less sedentary in their choice of active versus sedentary behaviors. On days I and 5, there were no contingencies for sedentary or active behaviors. During days 2 through 4, children in the Activity group were reinforced for being more active, and they significantly increased their activity and decreased time spent on preferred sedentary activities. Children in the Sedentary group were reinforced for not engaging in preferred sedentary behaviors, and they significantly decreased time spent on these sedentary behaviors, with lime reallocated both to being more active and to substitution of lower preference sedentary behaviors. Children randomized to the Control group were reinforced for attendance and made choices among the alternatives as usual, allocating most or their time during all 5 days for their preferred sedentary behaviors. These laboratory results support the idea that activity can be increased by either reinforcing children for being more active or for reducing lime spent in sedentary activities.

Tobacco abstinence, smoking cues, and the reinforcing value of smoking

One definition of the reinforcing value of a drug is the degree to which an organism will work to obtain it. Male and female smokers (n = 8 each) engaged in a task involving concurrent schedules of reinforcement for responding to receive cigarette puffs versus money on four occasions, following overnight abstinence versus no abstinence and in the presence of a lit cigarette (smoking "cue") or with no cigarette (2 x 2 design). Reinforcement schedule for puffs ranged from variable ratio 4 (VR4) to VR32, with schedule order during the first five trials (VR4 first, VR32 first) counterbalanced and repeated in reverse sequence during the second five trials. Schedule for money remained at VR4 during all trials. Results indicated significantly greater responding for puffs after overnight abstinence and in the presence of the smoking cue, although effect of the cue was specific to the "leaner" VR schedules (VR16, VR32). Unexpectedly, not only was reinforcement schedule for puffs a significant determinant of responding, but the order of these schedules (i.e., VR4 first vs. VR32 first) produced a significant overall difference in responding for puffs, especially in the presence of the cue. There was no difference in responding between males and females. These findings indicate that the reinforcing value of smoking is increased by overnight abstinence, the presence of a lit cigarette under lean reinforcement conditions, and the order in which reinforcement schedules are presented.

Predictors of adult humans' self-control and impulsiveness for food reinforcers

Humans vary in the degree to which they demonstrate self-control--choice of larger, more delayed over smaller, less delayed reinforcers. When reinforcers consist of food, individual human subjects' choice behavior varies from virtually exclusive self-control to exclusive impulsiveness. The present experiment, using 26 men and 26 women subjects, explored some possible sources of this individual variation through assessing the correlation of behaviors exhibited in the self-control paradigm with various subject characteristics. The results suggest that self-control is negatively related to individuals' reported susceptibility to hunger (Factor 3 of the Three-Factor Eating Questionnaire) and positively related to overall rating of juice desirability, but not to gender or to various measures of caloric deprivation or personality. Relatively high self-perceived levels of food deprivation may decrease self-control, whereas assigning a relatively high value to the reinforcer may increase self-control. Both tendencies would have been adaptive for evolving humans.

Behavioral economic analysis of food choice in obese children

Behavioral economic analysis has shown food choice in normal weight adults is influenced by both liking and constraints on access to food. The present study assessed the contributions of food liking and environmental constraints to choice of moderately liked, low-calorie foods or highly liked high-calorie foods in obese children. Access to the moderately liked food remained on a VR2 schedule, while response requirements for the highly liked food ranged from VR2 to VR32. Subjects chose to work for the higher-rated food at comparisons up to VR2/VR4, showed no preference at VR2/VR8 and their choice shifted to the lower rated food when response requirements for the highly liked food were increased to VR16. These results show that both subjective and environmental factors contribute to children's choice of foods.

Self-control and impulsiveness in adult humans when food is the reinforcer

Moderately food- and water-deprived women repeatedly chose between longer access to juice after a long delay (the self-control alternative), and shorter access to juice after a short delay (the impulsive alternative). In contrast to previous experiments using points exchangeable for money as the reinforcer, which have found consistent self-control across subjects, behavior of the present subjects varied between complete self-control and complete impulsiveness. Individual subjects' degree of self-control was not related to their majors, to their past or present degree of reported actual food deprivation, to their ratings of desire for the juice, or to their latency to respond. However, subjects who reported that they were currently dieting were significantly more impulsive; they obtained juice earlier within individual trials but had smaller total juice access time. The operant conditioning laboratory paradigm developed for the present research can be useful in investigating general determinants of self-control and impulsiveness for food reinforcers, as well as in investigating the origins of individual differences in food choice.

Behavioral economic analysis of smoking: money and food as alternatives

The relative reinforcing value of smoking versus two nonpharmacological reinforcers, money and food, was evaluated in young female smokers in two experiments. In Experiment 1 eight smokers worked for access to smoking or money on concurrent progressive variable ratio schedules of reinforcement (VR4 to VR50) across two days of Smoking Deprivation or No Deprivation. During No Deprivation money was reliably chosen over smoking. During Deprivation subjects initially (VR4) chose smoking over money, but at subsequent comparisons allocated equal time to work for smoking or money. In Experiment 2 eight smokers were provided access to smoking or food across four conditions: No Deprivation, Smoking Deprivation, Food Deprivation and Smoking + Food Deprivation, using the same progressive variable ratio schedules as in Experiment 1. Results showed an increase in the reinforcing value of food after Food Deprivation and smoking after Smoking Deprivation. On the dual deprivation day, subjects initially (VR4) chose to work for food, showed equal preferences over the next three schedule comparisons (VR8-VR20), and from VR25-VR50 shifted their choice to smoking. An increase in percent of calories as fat was observed during all deprivation conditions. The results demonstrate the use of the concurrent schedule paradigm for assessing choice among pharmacological and nonpharmacological reinforcers, and shows the relative reinforcing value of smoking depends on recent deprivation, response demands to obtain the reinforcer and availability of alternative reinforcers.