Food liking, food wanting, and sensory-specific satiety

Modular Maximization Theory: A functional account of economic behavior in laboratory animal models with applications to drug-seeking behavior

Substance abuse research depends on precise and sensitive assessments of reinforcer efficacy in animal models. However, conventional methods often lack theoretical rigor and specificity to support these assessments. To address these gaps, the Modular Maximization Theory (MMT) is introduced as a comprehensive framework for understanding instrumental behavior. Like earlier maximization theories, MMT posits that behavior is distributed across alternatives to maximize utility over time. This concept is structured through five foundational postulates that define alternative actions and rules for choosing between them as budget constraints and utility functions. A key innovation of MMT is its incorporation of reinforcer utilization-encompassing both consummatory and post-consummatory activities-into the budget-constraint function. A model of ratio-schedule performance is developed under the assumption that utilization is proportional to demand, with utility represented as an additive power function of reinforcer magnitude. This model, termed PURSPU (Proportional Utilization, Ratio Schedule, Power Utility), effectively explains how reinforcer magnitude, response effort, non-contingent reinforcement, and income influence demand curves, behavior-output functions, dose-response relationships, and progressive-ratio breakpoints, while accounting for rate-dependent effects. The model also offers novel insights into choice behavior, including concurrent-schedule performance, income dependency, and delay discounting, as well as post-reinforcement pauses and run rates. Variations in budget constraints and utility functions are proposed as alternative models. Potential theoretical advancements, more targeted assessments of drug abuse liability, and the broader role of MMT in understanding human drug abuse are explored.

No evidence for goal priming or sensory specific satiety effects following exposure to ambient food odours

Sensory-specific satiety describes a decline in hedonic value of the taste of a food as it is consumed, relative to a non-consumed food - the pudding tummy phenomenon. Incentive motivation towards consumed foods has also been shown to decline. Interestingly, several studies report that brief exposure to food odours can also produce a sensory-specific satiety effect, in the absence of consumption, selectively reducing hedonic ratings and subsequent high calorie food choices. Yet, other studies report goal-priming effects of ambient odours, in which brief implicit exposure increases the hedonic value of odour congruent food options. The present study aimed to determine whether exposure to ambient food odours would enhance or reduce incentive motivation for associated foods. Participants completed either an ambient odour (N = 38) or food consumption (N = 40) task. In both, participants were randomly assigned to an indulgent (chocolate) or non-indulgent (orange) food group and completed two blocks of a cross-modality matching grip-force task. One block was completed immediately before, the other immediately after, odour exposure/food consumption. A grip-force transducer measured effort exerted "to win" briefly presented (33 or 200ms) visual images of these foods, relative to control stimuli. In both studies, participants exerted greater effort to win the food items than control images. While neither satiety nor priming effects were found following ambient odour exposure, a classic sensory-specific satiety effect was found in the food consumption study. That is, force exerted for chocolate images declined significantly following chocolate consumption, in the absence of any decline in motivation for orange stimuli. While differences in odour exposure findings could be explained by factors such as concentration, timing, and nature of exposure, questions remain about the robustness of previously reported odour induced satiety and priming effects.

Nutritional Fuelling for Microgravity Environment of Space Missions

Abstract:

Since the beginning of space missions, the food systems have undergone a sea change with prolonged manned missions and permanent space habitats. We have a better understanding of physiological changes which happen in humans in space and help in adaptation to the space environment. Yet, much remains underexplored and warrants further research.

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Space missions today involve a considerable number of individuals operating in a microgravity environment for both short and long periods. The provision of food for such missions and managing the physio-pathological changes that affect nutritional requirements continue to be challenging. Food systems (food and beverages) used during every program to date have been shelf‐stable and were composed primarily of rehydratable or thermostabilized food items. Such foods usually have a lower hedonic value than fresh or frozen foods. Consequently, a reliable food system must provide a wide range of palatable and attractive foods as well as the tools to prepare them (through rehydration, heating, and cooling) to enhance the taste sensation of the crew. Adequate nutrition with easily accessible food is essential to this effort. To deliver nutritional recommendations to crew members for long-duration space missions, it is important to understand how nutritional status and general physiology are linked and affected by microgravity exposure. In view of this, it has been pointed out that nutritional countermeasures could rectify the physiological and behavioural anomalies during microgravity exposure. In this comprehensive narrative review, we have provided an overview of a few recent advances such as silkworm protein, good mood-vegan diet, 3-D food printing, and space garden’s produce for onboard support to food systems. It has also been found that exercise could be an addition to nutritional interventions. Areas of space exploration that require more in-depth research using ground-based bed rest models, as well as inflight microgravity conditions, are highlighted.

Evidence that carbohydrate-to-fat ratio and taste, but not energy density or NOVA level of processing, are determinants of food liking and food reward

This virtual (online) study tested the common but largely untested assumptions that food energy density, level of processing (NOVA categories), and carbohydrate-to-fat (CF) ratio are key determinants of food reward. Individual participants (224 women and men, mean age 35 y, 53% with healthy weight, 43% with overweight or obesity) were randomised to one of three, within-subjects, study arms: energy density (32 foods), or level of processing (24 foods), or CF ratio (24 foods). They rated the foods for taste pleasantness (liking), desire to eat (food reward), and sweetness, saltiness, and flavour intensity (for analysis averaged as taste intensity). Against our hypotheses, there was not a positive relationship between liking or food reward and either energy density or level of processing. As hypothesised, foods combining more equal energy amounts of carbohydrate and fat (combo foods), and foods tasting more intense, scored higher on both liking and food reward. Further results were that CF ratio, taste intensity, and food fibre content (negatively), independent of energy density, accounted for 56% and 43% of the variance in liking and food reward, respectively. We interpret the results for CF ratio and fibre in terms of food energy-to-satiety ratio (ESR), where ESR for combo foods is high, and ESR for high-fibre foods is low. We suggest that the metric of ESR should be considered when designing future studies of effects of food composition on food reward, preference, and intake.

Sensing the Snacking Experience: Bodily Sensations Linked to the Consumption of Healthy and Unhealthy Snack Foods-A Comparison between Body Mass Index Levels

The World Health Organisation (WHO) has highlighted the need for immediate action regarding the escalating global prevalence of overweight and obesity. Based on the need for long-term strategies supporting dietary behaviour changes, the concept of 'interoception' (i.e., sensing the body's internal state) has been proposed as promising for understanding and controlling food intake behaviours. As eating behaviours are motivated by the need for securing energy demands as well as the desire for pleasure, investigating the bodily sensations perceived in relation to food consumption can support our understanding of human food and eating behaviours. Here, a consumer study was conducted on 286 Danish consumers to explore the interoceptive experience of snack food consumption. This study included an investigation of the consumers' interoceptive capabilities and ability to feel pleasure, intuitive eating behaviours, snack food consumption frequency, the drivers of snack food consumption, food-related pleasure, and post-ingestive sensations linked to snack food consumption. The study was conducted on consumers with different Body Mass Index (BMI) levels to study potential differences between these groups. The study showed normal interoceptive capabilities and abilities to feel pleasure, with no differences between BMI groups. Regarding intuitive eating, the study found intuitive eating to be more prevalent among the group holding normal BMI. No significant differences between BMI groups were found in terms of snack intake frequency. However, differences between BMI groups were found in terms of: the drivers of snack consumption, the aspects bringing food-related pleasure from snack consumption, and the post-ingestive sensations felt after eating snack foods.

Hedonic Overeating-Questionnaire: Exploring interactive effects between wanting, liking, and dyscontrol on body mass index

The Hedonic Overeating-Questionnaire is a brief self-report measure for the trait assessment of liking (pleasure to eat; consummatory reward component), wanting (food craving; anticipatory reward component), and dyscontrol (loss of control over eating). In the original validation study, higher scores on each of the three subscales related to higher body mass index (BMI). However, theories on food reward and self-regulation suggest that overeating and obesity may also result from interactions between these aspects. Therefore, we reanalyzed the data of the original, cross-sectional study (N = 2504, 53% female) and explored whether liking, wanting, and dyscontrol scores interactively predicted BMI. Indeed, there was a significant interaction effect Wanting × Dyscontrol on BMI such that higher dyscontrol scores related to higher BMI, particularly at high wanting scores. The other two-way interactions and the three-way interaction were not significant. Results do not support certain theories on food reward (e.g., the incentive-sensitization theory of addiction and its application to obesity), which would suggest an interactive effect between liking and wanting on BMI. However, they do support dual systems models of self-regulation that suggest that overeating and obesity result from an interplay of strong bottom-up impulses (here: wanting) and weak top-down control (here: dyscontrol).

An EEG study on the effect of being overweight on anticipatory and consummatory reward in response to pleasant taste stimuli

Two-thirds of adults in the United Kingdom currently suffer from overweight or obesity, making it one of the biggest contributors to health problems. Within the framework of the incentive sensitisation theory, it has been hypothesised that overweight people experience heightened reward anticipation when encountering cues that signal food, such as pictures and smells of food, but that they experience less reward from consuming food compared to normal-weight people. There is, however, little evidence for this prediction. Few studies test both anticipation and consumption in the same study, and even fewer with electroencephalography (EEG). This study sought to address this gap in the literature by measuring scalp activity when overweight and normal-weight people encountered cues signalling the imminent arrival of pleasant and neutral taste stimuli, and when they received these stimuli. The behavioural data showed that there was a smaller difference in valence ratings between the pleasant and neutral taste in the overweight than normal-weight group, in accordance with our hypothesis. However, contrary to our hypothesis, the groups did not differ in their electrophysiological response to taste stimuli. Instead, there was a reduction in N1 amplitude to both taste and picture cues in overweight relative to normal-weight participants. This suggests that reduced attention to cues may be a crucial factor in risk of overweight.

Should you "picture" this? Effects of picture-taking features of food diary apps on memory, liking, and wanting

Picture-taking functions are commonly available features in food diaries and other mobile applications that may influence how we think about the very food we consume. Because memories of food (Higgs & Donohoe, 2011) and the act of recording food consumption (Turk et al., 2013) have been shown to influence desire for and consumption of food, this paper investigated the effects of using the picture-taking feature of a food diary app on liking, wanting, and memory of food. Using a simple food diary app with a picture-taking feature loaded onto iPads, participants took part in a lab experiment where they either did or did not use the picture-taking feature of the app as they ate a snack. To capture the changes in liking and wanting that naturally occur as more food is consumed, participants were also randomly assigned to receive either larger or smaller portions of the snack. The results indicate that picture-taking while eating is associated with greater wanting of the food following consumption. Furthermore, for smaller portions of food, taking pictures during consumption is associated with greater liking of the food. However, taking pictures in the smaller portion size condition was also associated with less detailed recall of food's sensory properties.

Food reinforcement and habituation to food are processes related to initiation and cessation of eating

An individual bout of eating involves cues to start eating, as well as cues to terminate eating. One process that determines initiation of eating is food reinforcement. Foods with high reinforcing value are also likely to be consumed in greater quantities. Research suggests both cross-sectional and prospective relationships between food reinforcement and obesity, food reinforcement is positively related to energy intake, and energy intake mediates the relationship between food reinforcement and obesity. A process related to cessation of eating is habituation. Habituation is a general behavioral process that describes a reduction in physiological or affective response to a stimulus, or a reduction in the behavioral responding to obtain a stimulus. Repeated exposure to the same food during a meal can result in habituation to that food and a reduction in consumption. Habituation is also cross-sectionally and prospectively related to body weight, as people who habituate slower consume more in a meal and are more overweight. Research from our laboratory has shown that these two processes independently influence eating, as they can account for almost 60% of the variance in ad libitum intake. In addition, habituation phenotypes show reliable relationships with reinforcing value, such that people who habituate faster also find food less reinforcing. Developing a better understanding of cues to start and stop eating is fundamental to understanding how to modify eating behavior. An overview of research on food reinforcement, habituation and food intake for people with a range of weight status and without eating disorders is provided, and ideas about integrating these two processes that are related to initiation and termination of a bout of eating are discussed.

High reinforcing value of food is related to slow habituation to food

BACKGROUND

The rate of habituation to food and reinforcing value of food are processes that are related to food intake and body weight. Reinforcing value of food provides an index of the motivation to eat, while habituation provides an index on how repeated presentations of food relate to reduced behavioral and physiological responses to that food.

OBJECTIVE

To investigate the relationship between habituation phenotypes to salty, sweet and savory foods and reinforcing value of those foods.

DESIGN

A sample of 229 8-12-year-old children at risk for obesity completed reinforcing value and habituation tasks for foods that varied in savory, sweet or salty tastes. Multivariate Group Based Trajectory Modeling was used to create four unique patterns of habitation to foods based on detailed 10 s epochs of responding for food over a 24 min task. Differences in reinforcing value of food were assessed for these habituation phenotypes.

RESULTS

Results showed a graded relationship between the overall habituation phenotypes and reinforcing value of food, as those with the relatively flat habituation phenotype found food more reinforcing than those with phenotypes that showed rapidly decelerating responding across all taste categories.

CONCLUSIONS

Those who habituated slower found food more reinforcing than those with a rapid habituation phenotype. Implications of these phenotypes for understanding how habituation relates to food intake are discussed.

Associations between sweet taste function, oral complex carbohydrate sensitivity, liking and consumption of ad libitum sweet and non-sweet carbohydrate milkshakes among female adults

Excess energy intake is recognised as a strong contributing factor to the global rise of being overweight and obese. The aim of this paper was to investigate if oral sensitivity to complex carbohydrate relates to ad libitum consumption of complex carbohydrate foods in a sample group of female adults. Participants' ((n 51 females): age 23·0 (sd 0·6) years (range 20·0-41·0 years); excluding restrained eaters) sensitivity towards maltodextrin (oral complex carbohydrate) and glucose (sweet taste) was assessed by measuring detection threshold (DT) and suprathreshold intensity perception (ST). A crossover design was used to assess consumption of two different iso-energetic preload milkshakes and ad libitum milkshakes - (1) glucose-based milkshake, (2) maltodextrin-based milkshake. Ad libitum intake (primary outcome) and eating rate, liking, hunger, fullness and prospective consumption ratings were measured. Participants who were more sensitive towards complex carbohydrate (maltodextrin DT) consumed significantly more maltodextrin-based milkshake in comparison with less-sensitive participants (P = 0·01) and this was independent of liking. Participants who had higher liking for glucose-based milkshake consumed significantly more glucose-based milkshake in comparison with participants with lower hedonic ratings (P = 0·049). The results provide support regarding the role of the oral system sensitivity (potentially taste) to complex carbohydrate and the prospective to overconsume complex carbohydrate-based milkshake in a single sitting.

Behavioral and physiological characteristics associated with learning performance on an appetitive probabilistic selection task

Individuals show meaningful variability in food choices. Choices are affected by individual differences in sensitivity to food reward and punishment, so understanding correlates of response to food reinforcement can help characterize food choices. Here, we examined behavioral and physiological correlates of individual differences in how individuals learn from food reward and punishment, as measured by performance on an appetitive probabilistic selection task that used sweet and bitter tastes as reinforcement. Sensitivity to food reward, sensitivity to food punishment, and overall learning performance were measured in 89 adults. Multivariate linear regressions were used to test if variables including body mass index (BMI), external eating, emotional eating, behavioral inhibition/behavioral activation scales (BIS/BAS), and perceived sensitivity to reward and punishment (SPQ/SRQ) were associated with measures of learning performance. External eating (β=-.035, p=.019), BIS (β=-.066, p=.004), and SPQ (β=.003, p=.023) were associated with overall learning performance. BMI (β=-.000, p=.012), emotional eating (β=.055, p=.006), and external eating (β=-.062, p=.004) were associated with sensitivity to food reward. No variables were associated with sensitivity to food punishment. In post hoc analyses, the interaction of sex and SPQ was associated with overall performance (β=-.005, p=.025), such that the relationship was positive in women only (β=.006, p=0.002). Results support that, controlling for key individual characteristics, BMI and susceptibility to food cues are associated with lower sensitivity to food reward, which may affect future food choices and eating behavior.

Network organization during probabilistic learning via taste outcomes

Reinforcement learning guides food decisions, yet how the brain learns from taste in humans is not fully understood. Existing research examines reinforcement learning from taste using passive condition paradigms, but response-dependent instrumental conditioning better reflects natural eating behavior. Here, we examined brain response during a taste-motivated reinforcement learning task and how measures of task-based network structure were related to behavioral outcomes. During a functional MRI scan, 85 participants completed a probabilistic selection task with feedback via sweet taste or bitter taste. Whole brain response and functional network topology measures, including identification of communities and community segregation, were examined during choice, sweet taste, and bitter taste conditions. Relative to the bitter taste, sweet taste was associated with increased whole brain response in the hippocampus, oral somatosensory cortex, and orbitofrontal cortex. Sweet taste was also related to differential community assignment of the ventromedial prefrontal cortex and ventrolateral prefrontal cortex compared to bitter taste. During choice, increasing segregation of a community containing the amygdala, hippocampus, and right fusiform gyrus was associated with increased sensitivity to punishment on the task's posttest. Further, normal BMI was associated with differential community structure compared to overweight and obese BMI, where high BMI reflected increased connectivity of visual regions. Together, results demonstrate that network topology of learning and memory regions during choice is related to avoiding a bitter taste, and that BMI is associated with increased connectivity of area involved in processing external stimuli. Network organization and topology provide unique insight into individual differences in brain response to instrumental conditioning via taste reinforcers.

Effect of metabolic state on implicit and explicit responses to food in young healthy females

Recent neuroscience research has delineated key psychological components of reward: wanting, liking and learning. Each component is further divided into explicit and implicit processes. While explicit processes are consciously experienced, implicit processes are not always directly accessible to conscious inspection. In the present study, we investigated the effect of metabolic state on implicit and explicit responses and their relationship in food context, especially when foods and visually matched non-food items are contrasted, and when foods in a sole food context but differing in energy content (high-energy - low-energy) or taste (sweet - savoury) were contrasted. Sixty healthy non-obese females participated in the study in fasted and fed states. Three Implicit Association Tests were used to assess implicit associations. Explicit liking and wanting ratings were assessed by visual analogue scales. In the implicit food-non-food context, food was preferred over non-food items both in fasted and fed states, though the strength of implicit associations declined significantly from fasted to fed state. However, the direction or strength of implicit associations was not significantly different between the metabolic states when comparing concepts within food context only, differing in energy content or taste. Instead, explicit responses reflected the change in the metabolic state in a manner consistent with alliesthesia and sensory-specific satiety. The results of the present study suggest that implicit associations are relatively resistant to acute change in the metabolic condition compared to explicit ratings, which shift more readily according to the fasted-fed continuum. The shift in the prevailing metabolic state was, however, reflected in the strength of implicit responses towards food in relation to non-food items, yet in the sole food contexts implicit associations were comparable between the fasted and fed states.

Food Reward and Food Choice. An Inquiry Through The Liking and Wanting Model

What if consumers are getting obese because eating less calories is more difficult for persons that have a higher pleasure and desire towards food (Ikeda et al., 2005) and food companies do not help given only a two extreme option choice to satisfy their needs (i.e., low calories vs. high calories or healthy vs. unhealthy)? Reward systems are being described with a new conceptual approach where liking—the pleasure derived from eating a given food—and wanting—motivational value, desire, or craving—can be seen as the significant forces guiding eating behavior. Our work shows that pleasure (liking), desire (wanting), and the interaction between them influence and are good predictors of food choice and food intake. Reward responses to food are closely linked to food choice, inducing to caloric overconsumption. Based on the responses given to a self-administered questionnaire measuring liking and wanting attitudes, we found three different segments named ‘Reward lovers,’ ‘Half epicurious,’ and ‘Non indulgents’. Their behavior when choosing food is quite different. Results show differential effects on caloric consumption depending on segments. The introduction of more food choices that try to balance their content is a win-win strategy for consumers, companies, and society.

Choice is relative: Reinforcing value of food and activity in obesity treatment

Persons with obesity find high-energy-dense food and sedentary behaviors highly reinforcing. Diets and exercise programs deprive individuals of many favorite foods and activities, which can counterproductively heighten their value and lead to relapse. Since the value of reinforcers depend on the alternatives available, one approach to reducing food and sedentary activity reinforcement is to build healthy alternative reinforcers. Current behavioral treatment programs for children and adults do not attempt to build alternative reinforcers as substitutes for unhealthy behaviors to reduce the impact of food or activity deprivation on the motivation to eat or be inactive. A goal of the next generation of obesity treatment programs should focus on development of healthy behaviors as reinforcers so that people will be motivated to engage in them. This article provides an overview of relationships among reinforcers, how understanding substitutes and complements can influence eating and activity, and how enriching a person's environment and providing choice architecture can enhance weight control. Ideas for translation of these basic behavioral economic principles to obesity treatment programs are discussed. (PsycINFO Database Record (c) 2020 APA, all rights reserved).

Dynamic Changes in Post-Ingestive Sensations after Consumption of a Breakfast Meal High in Protein or Carbohydrate

The obesity epidemic urges exploration of several parameters that play an important role in our eating behaviours. Post-ingestive sensations can provide a more comprehensive picture of the eating experience than mere satiety measurements. This study aimed to (1) quantify the dynamics of different post-ingestive sensations after food intake and (2) study the effect of protein and carbohydrate on hedonic and post-ingestive responses. Forty-eight participants (mean age 20.4) were served a breakfast meal high in protein (HighPRO) or high in carbohydrate (HighCHO) on two separate days using a randomised controlled crossover design. Post-ingestive sensations were measured every 30 min, for 3 h post intake using visual analogue scale (VAS). Results showed a significant main effect of time for all post-ingestive sensations. HighCHO induced higher hedonic responses compared to HighPRO, as well as higher ratings for post-ingestive sensations such as Satisfaction, Food joy, Overall wellbeing and Fullness. HighPRO, on the other hand, induced higher ratings for Sweet desire post intake. The development of sensations after a meal might be important for consumers' following food choices and for extra calorie intake. More detailed knowledge in this area could elucidate aspects of overeating and obesity.

Forty-eight hour conditioning produces a robust long lasting flavor preference in rats

Conditioned flavor preference (CFP) learning is a form of associative learning in ingestive behavior. CFP Learning can be rapid and produces preferences of varying strengths that can be exceptionally persistent. We sought to establish a method to produce a robust long-lasting CFP in rats. Rats were given 48-h access (conditioning) to a CS+ flavor (grape or cherry 0.05% Kool-Aid, counterbalanced) mixed with 8% glucose and 0.05% saccharin. In order to determine the strength of conditioning rats were given 14 consecutive days of 24-h access to CS+ and CS- flavors mixed only with 0.05% Kool-Aid and 0.05% saccharin (extinction), then further tested 34 days after the last extinction test (48 days post conditioning) for 2 consecutive days with the CS+ and CS-. We found that not only did the learned CFP fail to extinguish over 14 days of testing, but it also persisted for at least 48 days after conditioning. These data provide a method to produce a robust, long lasting and persistent CFP for use in future ingestive behavior research.

Wanting and liking for sugar sweetened beverages and snacks differ following depletion and repletion with energy and fluids

Drinking sugar-sweetened beverages (SSBs) seems to uniquely contribute to excess weight gain, and several mechanisms have been proposed to account for this. Here we examine a further proposal, namely that explicit wanting and liking for SSBs may be less sensitive to changes in physiological state, when contrasted to equi-palatable solid sweet snacks. Study 1 explored this by having participants rate wanting for (on seeing) and liking of (on tasting) several SSBs and snacks, before and after receiving a solid lunch with ad libitum water. Participant reports of hunger and thirst, obtained at multiple time-points, equally reduced across lunch. Wanting for the snacks decreased significantly more across lunch than liking, but for the SSBs, wanting and liking decreased in parallel. Study 2 engineered a far more dramatic alteration in thirst, by using fluid deprivation, a liquid lunch, and encouraging drinking to satiation. This time, reduction in thirst exceeded reduction in hunger. However, all this served to achieve was an equivalent change across lunch for snacks and SSBs, with wanting reducing more than liking now for both. These findings suggest that changes in wanting, relative to liking, for SSBs, are less sensitive to alterations in physiological state than equi-palatable solid snacks, enhancing the chance of consumption.

An investigation of variety effects during operant responding in the rat utilizing different reward flavors

Humans and nonhuman animals respond to food diversity by increasing intake and appetitive behaviors, reflecting enhanced valuation for items presented in the context of variety. Previous work on food variety effects has posited two main explanatory mechanisms. Variety could slow habituation processes by decreasing exposure to a single food item or could elicit contrast effects in which comparisons between items impact relative valuation. This study used three flavors of sucrose rewards to investigate rats' responses to qualitative reward variety in different variety contexts: low (2 flavors) and high (3 flavors) conditions. Control sessions used only a single flavored pellet (no variety). Animals were tested in low (10 trials), moderate (20 trials) and high consumption (30 trials) sessions. A trial within each session was defined as completion of the operant response and acquisition of the reward pellet. Cues associated with flavors were used to examine predictability and between-trial ('micro') variety. Indicators of a variety effect were found including faster responding for rewards during the variety context compared to an initial control (no variety) context. This decrease in response latency continued to be observed for some measures in post-variety control contexts. The most robust statistical finding of variety effects was found using trial-by-trial analysis, with shorter response latencies obtained for trials with outcomes differing from the preceding trial compared to successive trials with identical outcomes. These results have implications for understanding how a general reward context like variety impacts behavior, and for informing clinical approaches focusing on motivation and eating disorders.

The effects of repeated exposure and variety on vegetable intake in pre-school children

Children's vegetable consumption in the UK remains lower than national recommendations, presenting potential long-term health risks. It is known that repeated exposure promotes intake of novel vegetables and that offering children variety and choice can also encourage intake. The current study aimed to compare the impact of offering variety over simple repeated exposure as a strategy for increasing pre-school children's vegetable consumption. Children (N = 95) aged 24-55 months were recruited through participating nurseries and assigned to receive repeated exposure (RE) to a single vegetable snack or a mixed snack consisting of five different vegetables (variety: V). A minimum of 5 (maximum 6) exposures were given for both RE and V conditions. Pre and post-intervention intake measures of both the RE and V snacks were taken for each child. Follow up measures took place 1 month post-intervention (n = 40). Vegetable intake increased significantly from pre to post intervention for snacks congruent to the condition to which children were assigned. Magnitude of change was smaller for the variety condition. Follow up data revealed that snack intake remained significantly higher than baseline 1 month post-intervention (p < 0.001). In agreement with previous work this study confirmed that repeated exposure was effective in promoting children's vegetable intake but there was no additional benefit of variety in this context. It may be that for moderately familiar vegetables, serving them alone encourages intake and for this age group, avoids contamination fears or effects of neophobia.

Pre- and postprandial variation in implicit attention to food images reflects appetite and sensory-specific satiety

Implicit attentional processes are biased toward food-related stimuli, with the extent of that bias reflecting relative motivation to eat. These interactions have typically been investigated by comparisons between fasted and sated individuals. In this study, temporal changes in implicit attention to food were assessed in relation to natural, spontaneous changes in appetite occurring before and after an anticipated midday meal. Non-fasted adults performed an emotional blink of attention (EBA) task at intervals, before and after consuming preferred, pre-selected sandwiches to satiety. Participants were required to detect targets within a rapid visual stream, presented after task-irrelevant food (preferred or non-preferred sandwiches, or desserts) or non-food distractor images. All categories of food distractor preferentially captured attention even when appetite levels were low, but became more distracting as appetite increased preprandially, reducing task accuracy maximally as hunger peaked before lunch. Postprandially, attentional capture was markedly reduced for images of the specific sandwich type consumed and, to a lesser extent, for images of other sandwich types that had not been eaten. Attentional capture by images of desserts was unaffected by satiation. These findings support an important role of selective visual attention in the guidance of motivated behaviour. Naturalistic, meal-related changes in appetite are accompanied by changes in implicit attention to visual food stimuli that are easily detected using the EBA paradigm. Preprandial enhancement of attention capture by food cues likely reflects increases in the incentive motivational value of all food stimuli, perhaps providing an implicit index of wanting. Postprandial EBA responses confirm that satiation on a particular food results in relative inattention to that food, supporting an important attentional component in the operation of sensory-specific satiety.

Order and session size effects on treatment discrimination: Case study liking for Dulce de Leche

This study aimed to evaluate the implications of the number of samples per panelist in experimental precision and relative efficiency of treatment comparisons when modelling order effects for Dulce de Leche samples using a Sudoku design. Precision is defined as small variance and relative efficiency is defined as smaller variance than other alternative. Both are related to increasing discrimination power. A series of 8 Sudoku 16×16 squares being 4 randomized independently and 4 others in the reverse order, was designed to allow a linear model fitting to experiments of different sizes (orders 1 to 4, 1 to 8, 1 to 12 and 1 to 16). Data from 112 panelists were kept. Responses were recorded using a nine-point hedonic scale. Data was analyzed using a mixed linear model panelist, order and treatment (sample) effects. Analysis has shown a pronounced order effect, showing a first sample effect overestimation. Moreover, it was noted that order effect was rather evidenced in the first four orders, making for a relatively more precise experiment than the ones using remaining samples. Therefore, the use of Sudoku can be a convenient strategy to organize smaller testing sessions that could result in efficient experiments, with small variance of the estimated averages or effects and needing a lot less panelists to make a design as efficient as the large one used. Moreover, Sudoku can also inspire an efficient design that allows different test sessions.

Assessment of the relationship between food addiction and nutritional status in schizophrenic patients

OBJECTIVE

Obesity is one of today's most important public health problems. It is suggested that overeating and substance addiction show similarities, and addiction to food may be an important factor in the obesity epidemic. This study aimed to determine the prevalence of food addiction among schizophrenic patients and to examine the relationship between food addiction and anthropometric measurements and dietary nutrient intake.

METHODS

Study participants included a total of 104 schizophrenic outpatients, 62 females and 42 males. Food addiction was assessed by using the Yale Food Addiction Scale, and the anthropometric measurements of participants and their three-day food consumption were recorded.

RESULTS

This study found that more than half of the schizophrenic patients (60.6%) had food addiction, and that female schizophrenic patients had a higher prevalence (62.9%) of food addiction than male patients (57.1%). More than one-third of the schizophrenic patients with food addiction (41.3%) were found to be obese and their BMI, body weight, waist circumference, and body-fat ratio were higher than those of schizophrenic patients who did not have food addiction (P > 0.05). Moreover, the schizophrenic patients with food addiction were found to take significantly more energy, carbohydrate, and fat in their diet (P < 0.05).

CONCLUSION

It was observed that the development of food addiction in schizophrenic patients increased the risk of obesity and cardiovascular diseases, which were found to be at higher levels in these patients. Educational programs should be planned for these patients to acquire health dietary habits and to increase their physical activity levels, and an additional psychosocial support should be provided for patients with food addiction.

Explicit wanting and liking for palatable snacks are differentially affected by change in physiological state, and differentially related to salivation and hunger

Incentive salience theory (IST) suggests that 'wanting' and liking are dissociable processes. We argue that explicit measures of wanting in humans can reflect the impact of implicit 'wanting' as envisaged by IST, suggesting that dissociations should also be evident for explicit judgments of wanting and liking. To test this, participants were asked to make ratings of these variables for 8 palatable snack foods - and in a related test salivation rate was also assessed. Participants viewed and sniffed each snack food and rated wanting, and then sampled it and rated liking and whether they wanted more of it. Following a lunch eaten to satiety, and composed in part of half of the palatable snack foods, participants repeated their evaluations of the snack foods (and salivation rate). Liking changed less across lunch than wanting and want more ratings, the last-mentioned changing the most. Change in liking was associated with change in salivation rate, independent of wanting, and change in wanting was associated with change in hunger independent of liking. We argue these dissociations are consistent with 'wanting' influencing explicit wanting, and that want more ratings may represent a 'purer' measure of IST 'wanting'.

ROBucket: A low cost operant chamber based on the Arduino microcontroller

The operant conditioning chamber is a cornerstone of animal behavioral research. Operant boxes are used to assess learning and motivational behavior in animals, particularly for food and drug reinforcers. However, commercial operant chambers cost several thousands of dollars. We have constructed the Rodent Operant Bucket (ROBucket), an inexpensive and easily assembled open-source operant chamber based on the Arduino microcontroller platform, which can be used to train mice to respond for sucrose solution or other liquid reinforcers. The apparatus contains two nose pokes, a drinking well, and a solenoid-controlled liquid delivery system. ROBucket can run fixed ratio and progressive ratio training schedules, and can be programmed to run more complicated behavioral paradigms. Additional features such as motion sensing and video tracking can be added to the operant chamber through the array of widely available Arduino-compatible sensors. The design files and programming code are open source and available online for others to use.

A sipometer for measuring motivation to consume and reward value of foods and beverages in humans: Description and proof of principle

New methods, derived from animal work, for measuring food reward value (i.e. reinforcing value of food), and motivation (i.e. strength of desire) to consume, in humans are described and validated. A sipping device (sipometer) was developed that permits access to a liquid food or beverage on two reward schedules: continuous reinforcement (CR) and progressively increasing time spent exerting pressure on a straw (PR-schedule). In addition, a pictorial scale showing a cup, from which the 'amount wanted' could be marked was used to pre-test potential consumption. Intake, time spent sipping, breakpoint, and pressure exerted were the main dependent variables measured. Three pilot experiments were conducted. In Experiment 1, participants (n=8) consumed yogurt shakes after a 1-h or 21-h food deprivation period on both schedules. In Experiment 2, participants (n=8) sham-consumed (i.e. spit out) sweet and non-sweet beverages, utilizing both schedules. In Experiment 3, sham-consuming sweet and non-sweet beverages on both schedules and working for shake on the PR schedule were repeated, after three nights of either habitual sleep or short sleep duration (n=7) in a crossover design. In Experiment 1, participants sipped longer after 21-h vs. 1-h of food deprivation (13±3.0 vs. 8.0±2.1s; p=0.04), on the PR schedule. In Experiment 2, sham-intake (p=0.01) and sipping time (p=0.04) were greater for sweet than non-sweet beverages on the PR schedule and a similar, though not conventionally significant, effect was observed for exerted pressure (p=0.09). In both Experiment 2 and Experiment 3 after habitual sleep, on the PR schedule, cumulative pressure difference between sweet and non-sweet beverage increased with difference in amount wanted in the taste test. In contrast, after short sleep participants were less willing to work for sweet taste as their wanting increased, suggesting that sleep deprivation raises desire, but lowers behavioral output. Taken together these results demonstrate that the sipometer and associated ratings are reliable and useful measures of motivation to consume and reward value in humans. Participants were more motivated to obtain access to sweet beverages, especially when these were better liked than to obtain access to non-sweet beverages.

"The next mouthful will be the best": influence of prevision of the pleasure on the decision of having a second helping of a just eaten food

PURPOSE

Firstly, to see if the decision to have a second helping of food is related to the current evaluation of its palatability or to the predicted pleasure of a second helping of the same food. Secondly, to see if there is any relationship between subjects' BMI, their current or predicted evaluation of food palatability and their decision to have a second helping.

METHODS

128 guests attended a village festival with the specific purpose of eating a traditional, local soup made of beans and bacon. Subjects were asked to indicate the pleasure they felt eating the soup and the pleasure they predicted they would feel by having a second helping of the same food. Subjects were then offered a second identical portion of the above described soup.

RESULTS

72 subjects accepted a second helping of the soup. We discovered a significant correlation between predicted pleasure and the decision to have a second helping of the same food. There was also a significant correlation between BMI and the level of predicted pleasure of a second helping.

CONCLUSIONS

The decision to have a second helping of food was related to predicted pleasure and not to the pleasure that was experienced during the first helping.

Sensory specific satiety: More than 'just' habituation?

Sensory specific satiety (SSS) describes the decline in pleasantness associated with a food as it is eaten relative to a food that has not been eaten (the ‘eaten’ and ‘uneaten’ foods, respectively). The prevailing view is that SSS is governed by habituation. Nevertheless, the extent to which SSS results solely from this ‘low-level’ process remains unclear. Three experiments were conducted to explore the hypothesis that ‘top-down’ cognitive activity affects the expression of SSS; specifically, we manipulated participants' expectations about whether or not they would have access to alternative test foods (uneaten foods) after consuming a test meal (eaten food). This manipulation was motivated by ‘Commodity Theory,’ which describes the relative increase in value of a commodity when it becomes unavailable. We tested the hypothesis that a decline in the pleasantness and desire to eat the eaten food is exaggerated when uneaten foods are unavailable to participants. None of our findings supported this proposition – we found no evidence that SSS is dependent on top-down processes associated with the availability of other uneaten test foods.

Effects of a mindfulness-based intervention on mindful eating, sweets consumption, and fasting glucose levels in obese adults: data from the SHINE randomized controlled trial

We evaluated changes in mindful eating as a potential mechanism underlying the effects of a mindfulness-based intervention for weight loss on eating of sweet foods and fasting glucose levels. We randomized 194 obese individuals (M age = 47.0 ± 12.7 years; BMI = 35.5 ± 3.6; 78% women) to a 5.5-month diet-exercise program with or without mindfulness training. The mindfulness group, relative to the active control group, evidenced increases in mindful eating and maintenance of fasting glucose from baseline to 12-month assessment. Increases in mindful eating were associated with decreased eating of sweets and fasting glucose levels among mindfulness group participants, but this association was not statistically significant among active control group participants. Twelve-month increases in mindful eating partially mediated the effect of intervention arm on changes in fasting glucose levels from baseline to 12-month assessment. Increases in mindful eating may contribute to the effects of mindfulness-based weight loss interventions on eating of sweets and fasting glucose levels.

Food reward. What it is and how to measure it

We investigated the contribution of hunger and food liking to food reward, and the relationship between food reward and food intake. We defined liking as the pleasantness of taste of food in the mouth, and food reward as the momentary value of a food to the individual at the time of ingestion. Liking and food reward were measured, respectively, by ratings of the pleasantness of the taste of a mouthful, and ratings of desire to eat a portion, of the food in question. Hunger, which we view as primarily the absence of fullness, was rated without food being present. Study 1 provided evidence that hunger and liking contribute independently to food reward, with little effect of hunger on liking. Food intake reduced liking and reward value more for the eaten food than uneaten foods. The results were ambiguous as to whether this food-specific decline in reward value ('sensory-specific satiety') involved a decrease in 'wanting' in addition to the decrease in liking. Studies 2 and 3 compared desire to eat ratings with work-for-food and pay-for-food measures of food reward, and found desire to eat to be equal or superior in respect of effects of hunger and liking, and superior in predicting ad libitum food intake. A further general observation was that in making ratings of food liking participants may confuse the pleasantness of the taste of food with the pleasantness of eating it. The latter, which some call 'palatability,' decreases more with eating because it is significantly affected by hunger/fullness. Together, our results demonstrate the validity of ratings of desire to eat a portion of a tasted food as a measure of food reward and as a predictor of food intake.

Touch satiety: differential effects of stroking velocity on liking and wanting touch over repetitions

A slow, gentle caress of the skin is a salient hedonic stimulus. Low threshold, unmyelinated C-tactile afferents fire preferentially to this type of touch, where slow (<1 cm/s) and fast (>10 cm/s) stroking velocities produce lower firing frequencies and are rated as less pleasant. The current aim was to investigate how the experience of tactile pleasantness changes with repeated exposure (satiety to touch). A further aim was to determine whether tactile satiety varied with different stroking velocities. The experimental paradigm used a controlled brush stroke to the forearm that was delivered repeatedly for ∼50 minutes. In Experiment 1, brush strokes were administered at three different velocities (0.3 cm/s, 3 cm/s and 30 cm/s), which were presented in a pseudo-randomised order. In Experiment 2, brush strokes were applied using only one velocity (either 3 or 30 cm/s). After each stroke, the participants rated both subjective pleasantness (liking) and wanting (the wish to be further exposed to the same stimulus) for each tactile sensation. In Experiment 1, both pleasantness and wanting showed a small, but significant, decrease over repetitions during stroking at 3 cm/s only, where the mean values for pleasantness and wanting were similar. Conversely, slower (0.3 cm/s) and faster (30 cm/s) stroking showed no decrease in ratings over time, however pleasantness was rated higher than wanting. In Experiment 2, both pleasantness and wanting showed a significant decrease over repetitions for both applied velocities, with a larger decrease in ratings for stroking at 3 cm/s. In conclusion, satiety to touch occurred with a slow onset and progression, where pleasantness and wanting ratings to stroking at 3 cm/s were affected more than at the slower or faster velocities. Tactile satiety appears to differ compared to appetitive and olfactory satiety, because the hedonic and rewarding aspects of touch persist for some time.