Food-related stimuli increase desire to eat in hungry and satiated human subjects

In the present study, the effect of food-related cues on the desire to eat chocolate in hungry and satiated subjects was investigated. Subjects (n=46) were randomly assigned to either a hungry or satiated group and then assigned to a group receiving one of the following stimuli: taste (2 M&Ms), sight (a photograph of M&Ms), cognition (a passage describin M&Ms), or control (no stimulus). In each testing session, subjects rated their desire to eat chocolate before and after the 90-s presentation of the particular stimulus. Each subject was then given a half pound of M&Ms so that actual consumption could also be measured. Results indicated that, following the presentation of the sight and taste stimuli, the subjects’ desire to eat chocolate was significantly increased. Furthermore, no differences in chocolate consumption due to state of hunger or type of food-related stimulus presented were found.     

Hunger-related intrusive thoughts reflect increased accessibility of food items

The elaborated intrusion model (Kavanagh, Andrade, & May, 2005) argues that a craving episode begins with a desire-related intrusive thought. This study tests the assumption that such intrusive thoughts, during hunger, reflect an increase in accessibility of food-related information in memory. Fifty-six undergraduates were randomly assigned to hungry or satiated conditions. Hunger was manipulated by asking the “hungry” group to abstain from eating breakfast and snacks prior to testing before lunch, while the “satiated” group was asked to eat normally and attend testing after lunch. Participants completed a lexical decision task containing food-related and neutral words, an intrusive thoughts questionnaire and a hunger questionnaire. Priming for food-related items relative to neutral on the lexical decision task was higher for hungry participants than satiated participants. Priming correlated strongly with frequency of food-related intrusive thoughts during the task. We conclude that desire-related lexical decision priming could provide a useful objective correlate of proneness to desire-related intrusions.     

Hungry for money: the desire for caloric resources increases the desire for financial resources and vice versa

This report attempts to provide an evolutionary explanation for humans' motivation to strive for money in present-day societies. We propose that people's desire for money is a modern derivate of their desire for food. In three studies, we show the reciprocal association between the incentive value of food and of money. In Study 1, hungry participants were less likely than satiated participants to donate to charity. In Study 2, participants in a room with an olfactory food cue, known to increase the desire to eat, offered less money in a give-some game compared with participants in a room free of scent. In Study 3, participants' desire for money affected the amount of M&M's they ate in a subsequent taste test, but only among participants who were not restricting their food intake in order to manage their weight.     

The interval between the CS and the UCS as a determiner of generalization performance

Rats were trained in a conditioned taste aversion paradigm in order to determine whether a trace interval between the conditioned stimulus (CS) and the unconditioned stimulus (UCS) would result in the forgetting of stimulus attributes. Accordingly, subjects were conditioned with milk (CS), given either an immediate or a delayed injection of lithium chloride (UCS), and tested 48 h later with either milk or chocolate milk, a generalized flavor. The rats conditioned immediately following the presentation of the CS avoided milk more than chocolate milk, indicating discrimination between the two flavors. Those conditioned after a trace interval avoided both flavors equally, suggesting a loss of stimulus attributes of the original CS. Delay rats, however, still exhibited substantial learning when compared with controls not experiencing the UCS. These results allege a role for the forgetting of stimulus attributes during a trace interval in addition to following a complete learning episode.     

Resistance to satiation: Reinforcing effects of food and eating under satiation

It has been shown previously that rats which have learned a response when hungry will continue to make that response when tested satiated, a phenomenon labeled resistance to satiation. Here we showed that rats which were previously trained hungry will learn a new response for the opportunity to consume pellets in a new situation when tested satiated. In four experiments various groups received each of the components of the training given when rats learn an instrumental response when hungry. Rats were placed in the goalbox of a straight alley and given food pellets when hungry or were hungry only in their home cages prior to running a straight alley in the satiated test in Experiment 1. In Experiments 2, 3, and 4 learning of a differential conditioning problem for pellets in S+ (nonreward in S?) was measured in the satiated test. Groups given pellets in their home cages when hungry with or without alley exposure learned to run more rapidly in S+ than in S? in the satiated test phase. The tendency to eat pellets in the apparatus and the reinforcing effect of eating the pellets was larger for rats which ate the pellets when hungry in their home cage than for rats which ate the pellets when satiated in their home cage. Being hungry in the home cage with no pellets was not sufficient to produce eating or running for pellets in the satiated test, indicating that any inherent reinforcing effect of the pellets is not sufficient to produce eating or running, and that incomplete satiation cannot account for the learning. These data indicate that a reinforcing effect of eating pellets under satiation is an important determiner of resistance to satiation.     

Effects of long- and variable-duration signals for food on activity,instrumental responding,and eating

Incentive-motivation theories typically assume that the conditioning of appetitive motivation involves the same parameters as Pavlovian salivary conditioning. In contrast, the Soltysik-Konorski model asserts that drive is inhibited by stimuli closely associated with food (salivary CSs) and augmented by stimuli more loosely associated with food (long and variable CS-US interval). Experiment 1 examined this latter proposition. Sixty-four rats were given extensive exposure to each of four environmental CSs, two while hungry and two while satiated. Within each deprivation condition, food was given 30–300 sec after placement of the rats in one environment, and was not given in the other environment. Performance on three separate measures—activity, lever-pressing, and food consumption—was higher in the environments previously associated with food. Experiment 2 examined the effects of discrete stimuli presented in advance of eating; in accord with the results of Experiment 1, food consumption was greater after a stimulus (1- to 9-min duration) previously paired with food than after no stimulus or after a stimulus unpaired with food. The overall results indicate (a) that stimuli associated with food become capable of facilitating a variety of food-directed behaviors, possibly via the conditioning of a common appetitive system, and (b) that a close association between the stimuli and food is not essential for such conditing to occur.     

study of taste perception

Taste stimulus identification was studied in order to more thoroughly examine human taste perception. Ten replicates of an array of 10 taste stimuli—NaCl, KCl, Na glutamate, quinine.HCl, citric acid, sucrose, aspartame, and NaCl-sucrose, acid-sucrose, and quinine-sucrose mixtures—were presented to normal subjects for identification from a list of corresponding stimulus names. Because perceptually similar substances are confused in identification tasks, the result was ataste confusion matrix. Consistency of identification for the 10 stimuli (T ₁₀) and for each stimulus pair (T ₂) was quantified with measures derived from information theory. Forty-two untrained subjects made an average of 57.4% correct identifications. An averageT ₁₀ of 2.25 of the maximum 3.32 bits and an averageT ₂ of 0.84 of a maximum 1.0 bit of information were transmitted. In a second experiment, 40 trained subjects per-formed better than 20 untrained subjects. The results suggested that the identification procedure may best be used to assess taste function following 1–2 training replicates. The patterns of taste confusion indicate that the 10 stimuli resemble one another to varying extents, yet each can be considered perceptually unique.     

Emotional eating and Pavlovian learning: evidence for conditioned appetitive responding to negative emotional states

Appetitive learning has been demonstrated several times using neutral cues or contexts as a predictor of food intake and it has been shown that humans easily learn cued desires for foods. It has, however, never been studied whether internal cues are also capable of appetitive conditioning. In this study, we tested whether humans can learn cued eating desires to negative moods as conditioned stimuli (CS), thereby offering a potential explanation of emotional eating (EE). Female participants were randomly presented with 10 different stimuli eliciting either negative or neutral emotional states, with one of these states paired with eating chocolate. Expectancy to eat, desire to eat, salivation, and unpleasantness of experiencing negative emotions were assessed. After conditioning, participants were brought into a negative emotional state and were asked to choose between money and chocolate. Data showed differential conditioned responding on the expectancy and desire measures, but not on salivation. Specific conditioned effects were obtained for participants with a higher BMI (body mass index) on the choice task, and for participants high on EE on the unpleasantness ratings. These findings provide the first experimental evidence for the idea that negative emotions can act as conditioned stimuli, and might suggest that classical conditioning is involved in EE.     

The efficacy of “right” as a function of its relationship with reinforcement

The effects of the relationship between the presentation of a verbal stimulus (“right”) and an established reinforcer (M&Ms) on the reinforcement efficacy of the verbal stimulus was tested with three groups of retarded boys. Blocks of training and test trials alternated. During training of the Discriminative Group, “right” reliably preceded candy. For the Contiguous Group, “right” accompanied candy, and for the Random Group “right” and candy were programmed independently. “Right” promoted learning in the Discriminative Group but did not in the latter two groups. The results support Cairns' analysis of the often found failure of approval to be an effective reinforcer in laboratory tasks.     

Psychophysics of taste lateralization on anterior tongue

There have been very few investigations of the spatial properties of taste stimuli localized to specific areas of the oral cavity. This is surprising, since the spatial localization of taste sensations may contribute to the overall taste percept, much as do quality, intensity, and the temporal characteristics of tastes. The difficulty in eliminating the confounding factor of a tactile sensation may partially account for the paucity of such studies, since a gustatory stimulus cannot be presented as a liquid without a tactile component. As a step toward understanding the localizability of gustatory sensations, we designed a yoked stimulator and an experimental procedure to control for tactile cues. Lateral discrimination was evaluated at the tip of the tongue with four taste stimuli (sodium saccharin, sodium chloride, citric acid, and quinine hydrochloride) by presenting a taste and a blank solution simultaneously at two locations on the tongue. We found that subjects could lateralize all four taste stimuli in the absence of any discriminative tactile cues. Subjects' ability to lateralize varied as a psychometric function of the stimulus concentration. Detection thresholds, measured in a forced-choice two-interval staircase procedure with the same yoked stimulator that was used in the lateralization task, were always lower than lateralization thresholds, and both lateralization and detection thresholds were correlated within subjects. Subjects were unable to lateralize taste cues on a nongustatory surface under the upper lip at the highest tested concentrations, at which performance was 100% on a gustatory surface (dorsal anterior tongue). These results show that (1) taste compounds can be lateralized in the absence of any discriminative mechanical cue (but only on the gustatory epithelium) and (2) although the localization of a compound does not logically require conscious detection of the taste (cf. blind sight), subjects always detected a taste when they were able to lateralize.     

Counterconditioning reduces cue-induced craving and actual cue-elicited consumption

Cue-induced craving is not easily reduced by an extinction or exposure procedure and may constitute an important route toward relapse in addictive behavior after treatment. In the present study, we investigated the effectiveness of counterconditioning as an alternative procedure to reduce cue-induced craving, in a nonclinical population. We found that a cue, initially paired with chocolate consumption, did not cease to elicit craving for chocolate after extinction (repeated presentation of the cue without chocolate consumption), but did so after counterconditioning (repeated pairing of the cue with consumption of a highly disliked liquid, Polysorbate 20). This effect persisted after 1 week. Counterconditioning moreover was more effective than extinction in disrupting reported expectancy to get to eat chocolate, and also appeared to be more effective in reducing actual cue-elicited chocolate consumption. These results suggest that counterconditioning may be more promising than cue exposure for the prevention of relapse in addictive behavior.     

The addition of saccharin to taste cues affects taste preference conditioning in thirsty rats

Previous failures to condition preferences for the unacceptable taste cues sucrose octaacetate (SOA) and citric acid (CA) using a reverse-order, differential conditioning procedure (Forestell & LoLordo, 2000) may have been the result of low consumption of the taste cues in training or of their relatively low acceptability to rats that are thirsty and hungry. In the present study, rats that were thirsty but not hungry readily consumed the SOA and CA conditioned stimulus solutions in training. In test, stronger preferences were displayed for CS+ if the taste cues had been mixed in water (i.e., for the previously unacceptable taste cues) than if they had been made more acceptable by the addition of saccharin in training and test. In Experiment 2, again with rats that were thirsty but not hungry, stronger preferences for CS+ were observed when taste cues were presented in water in the test than when they were presented in saccharin. Addition of saccharin to the taste cues in test eliminated the preference for CS+.     

Both perceptual and conceptual factors influence taste-odor and taste-taste interactions

Observers are often asked to make intensity judgments for a sensory attribute of a stimulus that is embedded in a background of “irrelevant” stimulusdimensions. Under some circumstances, these background dimensions of the stimulus can influence intensity judgments for the target attribute. For example, judgments of sweetness can be influenced by the other taste or-odor qualities of a solution (Frank & Byram, 1988; Kamen et al., 1961). Experiments 1 and 2 assessed the influence of stimulus context, instructional set, and reference stimuli on cross-quality interactions in mixtures of chemosensory stimuli. Experiment 1 demonstrated that odor-induced changes in sweetness judgments were dramatically influenced when subjects rated multiple attributes of the stimulus as compared with when they judged sweetness alone. Several odorants enhanced sweetness when sweetness alone was judged, while sweetness was suppressed for these same stimuli when total-intensity ratings were broken down into ratings for the sweetness, saltiness, sourness, bitterness, and fruitiness of each solution. Experiment 2 demonstrated a similar pattern of results when bitterness was the target taste. In addition, Experiment 2 showed that the instructional effects applied to both taste-odorand taste-taste mixtures. It was concluded that the taste enhancement and suppression observed for taste-odor and taste-taste mixtures are influenced by (1) instructional sets which influence subjects’ concepts of attribute categories, and (2) the perceptual similarities among the quality dimensions of the stimulus.     

Salt taste detection: an R-index approach to signal-detection measurements

The R-index approach to the signal-detection P(A) index of sensitivity was used to measure taste sensitivity to NaCl solutions. The R-index is the predicted probability of the correct choice of a signal, for a given signal-noise pair. For flow-wise and sipwise presentation, R-indices did not fluctuate significantly, provided subjects could not see the stimuli yet to be presented, indicating a lack of systematic sensitivity drift. The simultaneous measurement of more than one signal strength with reference to a common noise stimulus was seen to be a viable and sensitive procedure. Comparison of flow-wise and sipwise presentation of stimuli using R-indices, indicated that the former elicited greater subject sensitivity to NaCl taste.     

A confusion matrix for the study of taste perception

Taste stimulus identification was studied in order to more thoroughly examine human taste perception. Ten replicates of an array of 10 taste stimuli--NaCl, KCl, Na glutamate, quinine. HCl, citric acid, sucrose, aspartame, and NaCl-sucrose, acid-sucrose, and quinine-sucrose mixtures--were presented to normal subjects for identification from a list of corresponding stimulus names. Because perceptually similar substances are confused in identification tasks, the result was a taste confusion matrix. Consistency of identification for the 10 stimuli (T10) and for each stimulus pair (T2) was quantified with measures derived from information theory. Forty-two untrained subjects made an average of 57.4% correct identifications. An average T10 of 2.25 of the maximum 3.32 bits and an average T2 of 0.84 of a maximum 1.0 bit of information were transmitted. In a second experiment, 40 trained subjects performed better than 20 untrained subjects. The results suggested that the identification procedure may best be used to assess taste function following 1-2 training replicates. The patterns of taste confusion indicate that the 10 stimuli resemble one another to varying extents, yet each can be considered perceptually unique.     

The effect of social cues on the eating behavior of obese and normal subjects1

Schachter's externality hypothesis suggests that overweight individuals are more likely to be induced to eat by salient external cues than normal weight individuals. While a range of studies have demonstrated the plausibility of this hypothesis in the case of sensory stimuli (e.g., taste cues), there is little evidence that the hypothesis applies to social stimuli. The current study examines this latter proposition by exposing male and female, overweight and normal weight subjects to a same-sex or opposite-sex peer model. Under the guise of engaging in a taste experiment, the subjects were either exposed to a model who tasted experiment, the subjects were either exposed to a model who tasted no crackers (no eat), one cracker (low eat), or twenty crackers (high eat). In addition, control model-absent conditions were also run for purposes of establishing baseline eating rates. If the externality hypotheses were to prevail in social domains, one would expect overweight subjects to be more prone to model the cracker-eating behavior of the peer than normal weight individuals. However, the findings indicate that all subject groups regardless of weight evidence a rather clear modeling effect and all subjects evidence social inhibition effects on their eating behavior as well. Several intriguing interactions among subject sex, model sex, subject weight, and social condition were also found. The discussion explores the relevance of an externality model of overweight eating in social domains, and focuses upon the interesting and somewhat distinct pattern of socially mediated eating exhibited by overweight females.     

Salt taste sensitivity and stimulus volume: sips and drops. Some implications for the Henkin taste test

Various presentation procedures and stimulus volumes were compared in their effect on salt taste sensitivity. For sodium chloride (NaCl) stimuli pipetted onto the tongue, subjects had comparable measured sensitivity to 10 ml and 1 ml volumes but a reduced sensitivity to 0.1 ml volumes. The greatest sensitivity was achieved with 10 ml sipped volumes. Modification of the Henkin dropwise triangular taste test, by increasing the stimulus volumes, increased subjects' sensitivity. Only the 1 ml pipette presentation increased the sensitivity of the Henkin procedure, albeit slightly, to the detection of changes in taste sensitivity, the purpose for which the procedure was actually designed. Such modification did not perturb salivary NaCl levels more than the regular Henkin procedure, so it would not be expected to introduce sensitivity drift.     

Experimentally induced taste aversions in humans: effects of overshadowing on acquisition.

This study used vection-induced symptoms of motion sickness as an unconditioned stimulus to condition food aversions in humans and to evaluate the efficacy of an overshadowing agent (novel flavored candy: CS2) to attenuate acquisition of the aversion. Subjects unfamiliar with a target food (CS1) were assigned to one of the following three groups which were identical except for order of exposure to stimuli: Taste Aversion Group (CS1-US-CS2-Test), Control Group (US-CS1-CS2-Test), and Overshadowing Group (CS1-CS2-US-Test). Subjects were tested on aversion ratings and consumption of the target flavor and ratings of the overshadowing agent. Subjects in the Taste Aversion group rated the target flavor as significantly more aversive and consumed less of it, although not significantly so, that did those in the Control group. The Overshadowing group consumed significantly more of the target food than did the Taste Aversion Group. Considering only subjects unfamiliar with the overshadowing agent, those in the Overshadowing group rated the agent (CS2) as significantly more aversive than the Taste Aversion and Control groups. Implications of these findings to taste aversions in humans are discussed.     

Imitative learning in Japanese quail (Coturnix japonica) depends on the motivational state of the observer quail at the time of observation

The 2-action method was used to examine whether imitative learning in Japanese quail (Coturnix japonica) depends on the motivational state of the observer quail at the time of observation of the demonstrated behavior. Two groups of observers were fed before observation (satiated groups), whereas 2 other groups of observers were deprived of food before observation (hungry groups). Quail were tested either immediately following observation or after a 30-min delay. Results indicated that quail in the hungry groups imitated, whereas those in the satiated groups did not, regardless of whether their test was immediate or delayed. The results suggest that observer quail may not learn (through observation) behavior that leads to a reinforcer for which they are unmotivated at the time of test. In addition, the results show that quail are able to delay the performance of a response acquired through observation (i.e., they show deferred imitation).     

Nausea in bulimic women in response to a palatable food

Nausea in response to an appetizing food stimulus was assessed in bulimic women and healthy control subjects. Nausea was assessed via subjects' self-report and changes in levels of plasma arginine vasopressin (AVP), a hormonal correlate of nausea. Converging evidence was obtained indicating that bulimic women experienced nausea in response to the sight, smell, or taste of the palatable food stimulus. The possibility that the observed nausea is a learned response that may contribute to the bulimic binge/purge pattern is discussed.