The utility of behavioral economics in expanding the free-feed model of obesity

Lack of Bmal1 leads to changes in rhythmicity and impairs motivation towards natural stimuli

Maintaining proper circadian rhythms is essential for coordinating biological functions in mammals. This study investigates the effects of daily arrhythmicity using Bmal1-knockout (KO) mice as a model, aiming to understand behavioural and motivational implications. By employing a new mathematical analysis based on entropy divergence, we identified disrupted intricate activity patterns in mice derived by the complete absence of BMAL1 and quantified the difference regarding the activity oscillation's complexity. Changes in locomotor activity coincided with disturbances in circadian gene expression patterns. Additionally, we found a dysregulated gene expression profile particularly in brain nuclei like the ventral striatum, impacting genes related to reward and motivation. Further investigation revealed that arrhythmic mice exhibited heightened motivation for food and water rewards, indicating a link between circadian disruptions and the reward system. This research sheds light on how circadian clock alterations impact the gene expression regulating the reward system and how this, in turn, can lead to altered seeking behaviour and motivation for natural rewards. In summary, the present study contributes to our understanding of how reward processing is under the regulation of circadian clock machinery.

The Use of Nonmonetary Outcomes in Health-Related Delay Discounting Research: Review and Recommendations

Delay discounting (DD) refers to the tendency to devalue an outcome as a function of its delay. Most contemporary human DD research uses hypothetical money to assess individual rates of DD. However, nonmonetary outcomes such as food, substances of misuse, and sexual outcomes have been used as well, and have advantages because of their connections to health. This article reviews the literature on the use of nonmonetary outcomes of food, drugs, and sexual outcomes in relation to health and reinforcer pathologies such as substance use disorders, obesity, and sexual risk behaviors, respectively, and makes a case for their use in discounting research. First, food, substances, and sex may be more ecologically valid outcomes than money in terms of their connections to health problems and reinforcer pathologies. Second, consistent trends in commodity-specific (i.e., domain) effects, in which nonmonetary outcomes are discounted more steeply than money, enhance variation in discounting values. Third, commodity-specific changes in discounting with treatments designed to change health choices are described. Finally, methodological trends such as test-retest reliability, magnitude effects, the use of hypothetical versus real outcomes, and age-related effects are discussed in relation to the three outcome types and compared to trends with monetary discounting. Limitations that center around individual preferences, nonsystematic data, and deprivation are discussed. We argue that researchers can enhance their DD research, especially those related to health problems and reinforcer pathologies, with the use of nonmonetary outcomes. Recommendations for future directions of research are delineated.

Information, ingestion, and impulsivity: The impact of technology-enabled healthy food labels on online grocery shopping in impulsive and non-impulsive consumers

Introduction

Unhealthy food consumption is a problem for society, companies, and consumers. This study aims to contribute to knowledge regarding such issues by investigating how technology-enabled healthy food labels can impact food choice in an online grocery store context. We conceptualized unhealthy and healthy food choice as a matter of impulsivity problems. Three technology-enabled healthy food labels were derived based on variables that might impact self-control, and their influence on food choice was investigated.

Methods

The empirical study consisted of three parts. In the first part, participants’ impulsivity was measured using an adjusting delay task. Part two investigated the effects of self-monitoring, pre-commitment, and social comparison-based technology-enabled healthy food labels on food choice in a hypothetical online grocery shopping setting using a choice-based conjoint experiment. Lastly, in the third part, three where demographical questions were asked.

Results

The results (n = 405) show that self-monitoring, pre-commitment, and social comparison-based technology-enabled healthy food labels had the most to least impact on food choice in that order. Furthermore, the results indicate that self-monitoring and pre-commitment labels had more impact on the choice for impulsive compared to non-impulsive participants. Similarly, the results indicate that social comparison had more impact on choice for non-impulsive participants. These findings suggest that self-monitoring of previous healthy food choices might be more effective than pre-commitment based on discounts for healthy food products. However, these differences were minor.

Discussion

This finding has managerial implications as grocery stores might increase their revenue by introducing self-monitoring labels in an online grocery shopping setting. Future research should investigate these technology-enabled healthy food labels in natural food purchase settings.

Delay discounting and obesity in food insecure and food secure women

OBJECTIVES

The relation between food insecurity (FI) and delay discounting (DD) and probability discounting (PD) for food and money was tested in women. In addition, discounting was tested as a variable that mediates the relation between obesity and FI.

METHOD

Women recruited from a community sample (N = 92) completed questionnaires. They completed the food choice questionnaire, the monetary choice questionnaire, measures for food and money probability discounting (which quantify sensitivity to risk aversion), and demographic measures.

RESULTS

Women with FI had higher rates of obesity and higher food DD compared to food-secure women. However, DD for money or probability discounting for food or money did not significantly differ between FI and food secure groups when controlling for significant covariates. Neither DD or PD significantly mediated the relation between FI and obesity.

CONCLUSIONS

These results suggest that FI is associated with greater impulsive food choice, but its association with other monetary discounting and probability discounting for food and money appears contingent upon other demographic factors. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Social preference in rats

Rats were given repeated choices between social and nonsocial outcomes, and between familiar and unfamiliar social outcomes. Lever presses on either of 2 levers in the middle chamber of a 3-chamber apparatus opened a door adjacent to the lever, permitting 45-s access to social interaction with the rat in the chosen side chamber. In Experiment 1, rats preferred (a) social over nonsocial options, choosing their cagemate rat over an empty chamber, and (b) an unfamiliar over a familiar rat, choosing a non-cagemate over their cagemate. These findings were replicated in Experiment 2 with 2 different non-cagemate rats. Rats preferred both non-cagemate rats to a similar degree when pitted against their cagemate, but were indifferent when the 2 non-cagemates were pitted against each other. Similar preference for social over nonsocial and non-cagemate over cagemate was seen in Experiment 3, with new non-cagemate rats introduced after every third session. Response rates (for both cagemate and non-cagemate rats) were elevated under conditions of nonsocial (isolated) housing compared to conditions of social (paired) housing, demonstrating a social deprivation effect. Together, the experiments contribute to an experimental analysis of social preference within a social reinforcement framework, drawing on methods with proven efficacy in the analysis of reinforcement more generally.

Blunted satiety in fatty Zucker rats

Levels of weight gain have hit an epidemic level with rates of overweight and obesity diagnoses topping all-time highs. Elevated body weight has been linked to increased rates of cardiac problems, blood pressure issues, and risk of developing type 2 diabetes. Leptin, a hormone produced by the body that is involved in energy balance by inhibiting hunger has been implicated as an underlying mechanism that differentially contributes to food-seeking motivation. Using a scientifically validated animal model of obesity, the fatty Zucker rat, which has mutated leptin receptor genes, leptin's role in behavioral motivation can be assessed. Animals were on a 2 -h food access restriction with one-hour access to rewards in session and one hour of free-feeding access. Pre-session and post-session food access differences were evaluated in looking at motivation for food rewards during satiation while responding on differing levels of fixed-ratio schedules. The results showed robust differential behavior from satiation, demonstrating a basis for a biological mechanism involving leptin sensitivity that could underlie obesity. Although further experimentation is needed, understanding leptin could help bridge the gap in our understanding of satiation and non-satiation.

Healthy Eating: Approaching the Selection, Preparation, and Consumption of Healthy Food as Choice Behavior

Healthy eating has important well-being and financial implications for our society. As such, it is critical that the field of behavior science and behavior analysis conduct more research in this area so that effective interventions may be developed. One barrier to addressing healthy eating may be conceptual. Far from being a single response, eating is comprised of a series of choice responses. These selection, preparation and consumption responses form a temporally delayed behavioral chain. When designing interventions to address healthy eating, therefore, one must not only consider the specific target response, but alternative response options, and the effect of changing one response on other choices in the chain. The purpose of this article is to refine the analysis of healthy eating behavior, provide examples of research conducted in this area, and discuss how these interventions may influence this chain of responses. It is hoped that by doing so, additional research will be conducted and disseminated so that individuals, organizations, and policy makers can implement more effective interventions for healthy eating.

The Demand Curve Analyzer: Behavioral economic software for applied research

Free and open-source software for applying models of operant demand called the Demand Curve Analyzer (DCA) was developed and systematically evaluated for use in research. The software was constructed to streamline the use of recommended screening measures, prepare suitable scaling parameters, fit one of several models of operant demand, and provide publication-quality figures. The DCA allows users to easily import price and consumption data into spreadsheet-based controls and to perform statistical modeling with the aid of a graphical user interface. The results from computer simulations and reanalyses of published study data indicated that the DCA provides results consistent with commercially available software that has been traditionally used to apply these analyses (i.e., GraphPadTM Prism). Further, the DCA provides additional functionality that other statistical packages do not include. Practical issues and future directions related to the determination of scaling parameter k, screening for nonsystematic data, and the incorporation of more advanced behavioral economic methods are also discussed.

Cost-based anorexia: A novel framework to model anorexia nervosa

Anorexia nervosa (AN) is an eating disorder that is thought to emerge through biological predisposition(s) within sociocultural context(s). Practical and ethical concerns limit study of the etiology of this disorder in humans, and in particular the biological aspects. Laboratory animal models have a pivotal role in advancing our understanding of the neurobiological, physiological and behavioral aspects of this disorder, and developing new treatment strategies. One shortcoming of animal models, including activity based anorexia (ABA) in rodents, is that they cannot fully capture the contextual aspects of AN. In this article we discuss the merits of an alternate approach, cost-based anorexia (CBA). CBA is conceptually founded in behavioral economics and its magnitude is influenced by several relevant contextual aspects of feeding.

High-fat diet alters weight, caloric intake, and haloperidol sensitivity in the context of effort-based responding

High-fat (HF) diets result in weight gain, hyperphagia, and reduced dopamine D2 signaling; however, these findings have been obtained only under free-feeding conditions. This study tested the extent to which HF diet affects effort-dependent food procurement and the extent to which dopamine signaling is involved. Male Sprague-Dawley rats consumed either a HF (n=20) or a standard-chow (n=20) diet. We assessed the sensitivity to effort-based reinforcement in 10 rats from each group by measuring consumption across a series of fixed-ratio schedules (FR 5-FR 300) under a closed economy and quantified performance using the exponential-demand equation. For each FR, acute injections of 0 or 0.1 mg/kg of haloperidol, a D2 antagonist, were administered to assess dopamine-related changes in consumption. Rats fed a HF diet consumed more calories and weighed significantly more than rats fed standard-chow. Food consumption decreased in both groups in an effort-dependent manner, but there were no group differences. Haloperidol reduced responding in an FR-dependent manner for both groups. Animals exposed to a HF diet showed an altered sensitivity to haloperidol relative to rats fed a standard diet, suggesting that HF diet alters sensitivity to DA signaling underlying effort-based food procurement.

Effects of a cafeteria diet on delay discounting in adolescent and adult rats: Alterations on dopaminergic sensitivity

Diet-induced obesity is a laboratory procedure in which nonhuman animals are chronically exposed to a high-fat, high-sugar diet (i.e. cafeteria diet), which results in weight gain, altered sensitivity to reward, and alterations in the dopamine D₂ system. To date, few (if any) studies have examined age-related diet-induced obesity effects in a rat model or have used an impulsive choice task to characterize diet-induced behavioral alterations in reward processes. We exposed rats to a cafeteria-style diet for eight weeks starting at age 21 or 70 days. Following the diet exposures, the rats were tested on a delay discounting task - a measure of impulsive choice in which preference for smaller, immediate vs larger, delayed food reinforcers was assessed. Acute injections of haloperidol (0.03-0.3 mg/kg) were administered to assess the extent to which diet-induced changes in dopamine D₂ influence impulsive food choice. Across both age groups, rats fed a cafeteria diet gained the most weight and consumed more calories than rats fed a standard diet, with rats exposed during development showing the highest weight gain. No age- or diet-related baseline differences in delay discounting were revealed, however, haloperidol unmasked subtle diet-related differences by dose-dependently reducing choice for the larger, later reinforcer. Rats fed a cafeteria diet showed a leftward shift in the dose-response curve, suggesting heightened sensitivity to haloperidol, regardless of age, compared to rats fed a standard diet. Results indicate that chronic exposure to a cafeteria diet resulted in changes in underlying dopamine D₂ that manifested as greater impulsivity independent of age at diet exposure.

Use of the Exponential and Exponentiated Demand Equations to Assess the Behavioral Economics of Negative Reinforcement

Abnormal motivation and hedonic assessment of aversive stimuli are symptoms of anxiety and depression. Symptoms influenced by motivation and anhedonia predict treatment success or resistance. Therefore, a translational approach to the study of negatively motivated behaviors is needed. We describe a novel use of behavioral economics demand curve analysis to investigate negative reinforcement in animals that separates hedonic assessment of footshock termination (i.e., relief) from motivation to escape footshock. In outbred Sprague Dawley (SD) rats, relief increased as shock intensity increased. Likewise, motivation to escape footshock increased as shock intensity increased. To demonstrate the applicability to anxiety disorders, hedonic and motivational components of negative reinforcement were investigated in anxiety vulnerable Wistar Kyoto (WKY) rats. WKY rats demonstrated increased motivation for shock cessation with no difference in relief as compared to control SD rats, consistent with a negative bias for motivation in anxiety vulnerability. Moreover, motivation was positively correlated with relief in SD, but not in WKY. This study is the first to assess the hedonic and motivational components of negative reinforcement using behavioral economic analysis. This procedure can be used to investigate positive and negative reinforcement in humans and animals to gain a better understanding of the importance of motivated behavior in stress-related disorders.