Social transmission of food preferences in Japanese monkeys (Macaca fuscata) after mere exposure or aversion training

In Experiment 1, 3 mother-child pairs of Japanese monkeys (Macaca fuscata) were given simultaneous choice tests between raisins and popcorn. The mothers and offspring showed different choice patterns. Cofeeding opportunities were then alternated with individual choice tests. In Experiment 2,2 other pairs were added. Each animal was again offered simultaneous choice tests between marshmallows and almonds. Food aversion conditioning was used to create different choice patterns for mothers and offspring. After cofeeding and choice tests, the differences in choice patterns disappeared in both experiments. The changes after contact with the other's eating pattern during cofeeding was as follows: foods consumed by either came to be eaten by both; foods consumed by both continued to be eaten by both; and foods consumed by neither continued to be ignored. The results provide evidence for social transmission of food preferences in this species.     

Social interaction modifies learned aversions, sodium appetite, and both palatability and handling-time induced dietary preference in rats (Rattus norvegicus)

In a series of four experiments, I examined the extent to which socially transmitted diet preference could counteract the effects of a learned aversion (Experiment 1), a palatability-based diet preference (Experiment 2), a polyethylene glycol 20,000-induced sodium appetite (Experiment 3), and a handling-time induced dietary preference (Experiment 4). I found that rats poisoned after eating a novel diet ate very substantial amounts of the averted diet following interaction with conspecifics that had eaten the averted diet. Following interaction with conspecifics that had eaten an unpalatable diet, rats offered a choice between palatable and unpalatable diets ate more than twice as much unpalatable diet as did controls lacking social experience. Sodium-deficient rats offered a choice between sodium-enriched and sodium-adequate diets ate less than half as much sodium-enriched diet, following interaction with conspecifics that had eaten sodium-adequate diet as did control rats lacking social experience. Rats offered a choice between isocaloric, roughly equipalatable foods with long and short handling times (e.g., sunflower seeds with and without shells) chose the food having the longer handling time after interacting with conspecifics eating that food. These findings suggest that social influence is a major factor in guiding diet selection by rats.     

Responses of observer rats (Rattus norvegicus) to complex, diet-related signals emitted by demonstrator rats

We explored the effects of complex, food-identifying signals emitted by demonstrator Long-Evans rats (Rattus norvegicus) on food preferences of their observers. In Experiments 1 and 2, observers identified each of 2 or 3 foods their demonstrators had eaten before interacting with observers. In Experiment 3, individual observers interacted with groups of demonstrators. Some of these demonstrators had eaten one food, some another. Observers then chose between the two foods. The greater the proportion of demonstrators in a group that had eaten a diet, the greater the proportion of that diet the observers ate. In Experiment 4, each observer interacted over several weeks with a series of demonstrators and preferred each of the foods its demonstrators had eaten. In sum, the food preferences of observers were affected by several different types of complex, food-identifying signals like those one might expect rats to encounter outside the laboratory.     

Enhancement of food aversion by exposure to a poisoned conspecific in Norway rats (Rattus norvegicus)

Two experiments were conducted to determine whether exposure to a poisoned conspecific enhances prior food aversion in rats. In Experiment 1, subjects were serially exposed to two foods, cocoa‐flavored and cinnamon‐flavored ones, and were then poisoned 1 h later. On the next day, they were exposed to a poisoned conspecific that had eaten a cocoa‐flavored food. On the subsequent choice test, subjects had an enhanced aversion to cocoa‐flavored food. The result was replicated in Experiment 2, in which a cinnamon‐flavored food was assigned as a target. The results are discussed in relation to previous findings.     

Question-induced cognitive biases in reports of dietary intake by college men and women

In two experiments, investigated how variations in questionnaire structure influence respondents' reports of two aspects of dietary intake--the frequency with which various food items are eaten and the sizes of the portions that are eaten. In Experiment 1, approximately 400 subjects, prior to making a frequency judgment, were asked to think either about a specific occasion or about all the occasions on which they had eaten a particular food. The thoughts that preceded the frequency judgment influenced that judgment: Thinking of the range of occasions on which a food is consumed resulted in higher frequency estimates than thinking only of the most recent occasion. In Experiment 2, the same subjects made judgments about their typical portion sizes of several foods relative to described standards. For only one of eight foods were estimates properly and significantly affected by differences among the described standards. These results suggest that respondents are not particularly sensitive to portion-size definitions. We consider the implications of these phenomena for the development of a general theory of the cognitive processes that subserve health-survey responding.     

Food choice in rats (Rattus norvegicus): the effect of exposure to a poisoned conspecific

Three experiments were conducted to examine the effects of exposure to a poisoned conspecific on subsequent food aversion in rats. In Experiment 1A, rats that had been aversively conditioned to a cocoa-flavored food were exposed to a poisoned conspecific that had eaten the same food. On the subsequent choice test, the animals increased their aversion to that food. These results were reconfirmed in Experiment 1B, in which a cinnamon-flavored food was used as the stimulus. In Experiment 2, subjects were first exposed to a poisoned conspecific and then conditioned to the food which the conspecific had eaten. On the test, they showed no sign of increased aversion to that food.     

Social identification of toxic diets by Norway rats (Rattus norvegicus)

In the present experiment, a naive rat (an observer) interacted with two conspecifics (demonstrators) that had recently eaten a diet unfamiliar to the observer, ate two unfamiliar foods in succession, one of which was the food its demonstrators had eaten, suffered toxicosis, and finally, was offered a simultaneous choice between the two diets it had eaten prior to toxicosis induction. During the choice test, observers exhibited an aversion to that diet their respective demonstrators had not eaten. This result indicates that exposure of a rat to conspecifics that have eaten a diet can act, as does actual ingestion of a diet, to reduce that diet's subsequent associability with toxicosis. I discuss this finding as suggesting that interaction with conspecifics may provide an alternative to individual trial and error learning in identification of toxic foods by rats that ingest a number of novel foods in succession before becoming ill.     

Lack of interference in long-term memory for socially learned food preferences in rats (Rattus norvegicus)

Outside the laboratory, rats (Rattus norvegicus) are likely both to interact with several conspecifics that have eaten various foods and to eat a variety of foods themselves before they encounter any particular food for which they have a socially enhanced preference. Here the authors examine the stability of rats' socially learned food preferences following 6 days of potentially disruptive ingestive experiences. The authors found that 6 days of (a) eating unfamiliar foods, (b) interacting with demonstrators that had eaten unfamiliar foods, or (c) both eating unfamiliar foods and interacting with demonstrators that had eaten those foods had no measurable effect on rats' socially learned food preferences. The stability of socially enhanced food preferences over time and despite potentially disruptive experiences is consistent with the view that social learning about foods is an important determinant of the food choices of free-living Norway rats.     

Changing food preference as a function of mood

The authors investigated the effect of mood on food selection. Participants (N = 98) indicated the likelihood of general eating and the likelihood of eating specific foods after reading and projecting themselves onto the events and emotions described in a sad and a happy vignette. Both men and women believed they were more likely to consume food following a happy versus a sad event, and men believed they were significantly more likely to eat than did women. However, the type of food men and women believed they would consume interacted with the type of event experienced. Vegetarian snack foods were more likely to be consumed following a happy versus a sad event, with men more likely to eat snack foods. Men did not significantly change in likelihood of consuming sweet foods as their mood changed. However, women believed they were more likely to consume sweet foods following a sad event. The authors discuss the results in terms of a self-medication hypothesis and the effect of carbohydrates on central serotonin and endogenous opioids. Overall, results demonstrated that mood influences belief in the likelihood of food selection.     

The role of pre-exposure to novel food tastes in activity-based conditioned taste avoidance

Rats were given differential exposure to three distinct and novel foods. One of these foods was exposed for 7 days; another for 2 days, and the last was not exposed. Next, half of the rats received six daily sessions in which a compound of the three flavors was followed by opportunities to run in wheels. The other rats received the food compound but without wheel running. On the next day, all rats were given a choice among the three food flavors presented concurrently in separate dishes. When the compound food had been followed by wheel running, rats ate little of the food given no pre-exposure, more of the food given 2 days of pre-exposure, and considerably more of the food given 7 days of pre-exposure. In comparison, rats who did not receive an opportunity to run ate equal and moderate amounts of the three foods. The results suggest that pre-exposure to a food’s taste produces latent inhibition that interferes with conditioned taste avoidance produced by pairing a taste (CS) with wheel running (US).     

Social transmission of flavor preferences in two species of hamsters (Mesocricetus auratus and Phodopus campbelli)

Golden hamsters (Mesocricetus auratus) and dwarf hamsters (Phodopus campbelli) interacted with a conspecific demonstrator that had recently consumed a flavored food. When given a choice between their demonstrator's flavor and another flavor, the dwarf hamsters preferred the flavor their demonstrator had eaten. Golden hamsters did not prefer their demonstrators' diets when the demonstrators were unrelated adults or littermates, but they did when the demonstrator was their mother. Videotaping the interactions between demonstrators and observers revealed that adult golden hamsters did not investigate foods hoarded by their demonstrators whereas dwarf hamsters did. These results are interpreted in terms of the stimuli that activate feeding behavior systems in these 2 hamster species.     

Preference for novel flavors in adult Norway rats (Rattus norvegicus)

The authors fed rats 1 of 2 distinctively flavored, roughly equipalatable diets for 3 days then offered them an ad libitum choice between the 2 diets. For 3 days, subjects exhibited a reduced relative intake of whichever diet they had previously eaten (Experiment 1). Such reduction in relative intake was as effective as a toxicosis-induced conditioned aversion in determining subjects' food choices (Experiment 2). The strength of exposure-induced reduction in relative intake did not depend on similarity of the 2 diets offered for choice either to each other or to subjects' maintenance diet (Experiment 3) but did require continuous exposure to a diet (Experiment 4). These experiments provide the first evidence of a robust, exposure-induced decrease infood preference in rats lasting for days rather than minutes.     

Responsivity to pain in rats changed by the ingestion of flavored water

Sprague-Dawley male rats drank flavored water and subsequent pain responsivity was assessed using a hot plate first after isotonic saline and later after either 2.75 (Experiment 1) or 2.5 (Experiment 2) mg/kg of morphine hydrochloride was injected. A 48-h exposure to any one of several different flavors resulted in a reduction of the analgesic effects of morphine as shown by an attenuation of the increased latency to paw lick caused by the morphine. This effect was independent of the amount consumed. A 26-h exposure to a flavor decreased pain reactivity before and after morphine as shown by an overall increase in latency to paw lick. This effect was not influenced by whether the normally preferred flavor was made aversive by a previous pairing with lithium chloride-induced illness. These findings are consistent with the idea that many flavors, independently of palatability and amount consumed, increase the release and utilization of endogenous opioids.     

Mere social knowledge impacts children's consumption and categorization of foods

How does social information affect the perception of taste early in life? Does mere knowledge of other people's food preferences impact children's own experience when eating? In Experiment 1, 5‐ and 6‐year‐old children consumed more of a food described as popular with other children than a food that was described as unpopular with other children, even though the two foods were identical. In Experiment 2, children ate more of a food described as popular with children than a food described as popular with adults. Experiment 3 tested whether different perceptual experiences of otherwise identical foods contributed to the mechanisms underlying children's consumption. After sampling both endpoints of a sweet‐to‐sour range (applesauce with 0 mL or 5mL of lemon juice added), children were asked to taste and categorize applesauce samples with varying amounts of lemon juice added. When classifying ambiguous samples that were near the midpoint of the range (2 mL and 3 mL), children were more likely to categorize popular foods as sweet as compared to unpopular foods. Together, these findings provide evidence that social information plays a powerful role in guiding children's consumption and perception of foods. Broader links to the sociality of food selection are discussed.     

What Causes Humans to Begin and End A Meal? A Role for Memory for What Has Been Eaten, as Evidenced by A Study of Multiple Meal Eating in Amnesic Patients

Although many factors have been proposed and studied as causes of onset and termination of meals by humans, little attention has been paid to memory for what has previously been eaten. We propose that a principal determinant of meal onset and cessation in humans is memory of when a last meal was eaten and how much was consumed. Knowledge that one has just eaten a culturally defined complete meal may be sufficient grounds for refusal of further food. This hypothesis was tested by studying two densely amnesic patients who had almost no explicit memory for events that occurred more than a minute ago, and who, in particular, usually failed to remember that they had just eaten a meal. Both patients (on three occasions each) readily consumed a second lunch when it was offered 10 to 30 min after completion of the first meal, and usually began to consume a third meal when it was offered 10 to 30 min after completion of the second meal. These findings suggest that memory for what has recently been eaten is a substantial contributor to the onset or cessation of eating of a meal.     

Male Wistar rats show individual differences in an animal model of conformity

Conformity refers to the act of changing one’s behaviour to match that of others. Recent studies in humans have shown that individual differences exist in conformity and that these differences are related to differences in neuronal activity. To understand the neuronal mechanisms in more detail, animal tests to assess conformity are needed. Here, we used a test of conformity in rats that has previously been evaluated in female, but not male, rats and assessed the nature of individual differences in conformity. Male Wistar rats were given the opportunity to learn that two diets differed in palatability. They were subsequently exposed to a demonstrator that had consumed the less palatable food. Thereafter, they were exposed to the same diets again. Just like female rats, male rats decreased their preference for the more palatable food after interaction with demonstrator rats that had eaten the less palatable food. Individual differences existed for this shift, which were only weakly related to an interaction between their own initial preference and the amount consumed by the demonstrator rat. The data show that this conformity test in rats is a promising tool to study the neurobiology of conformity.     

Evaluating the efficacy of pictorial preference assessments with children who engage in food selectivity

Preference assessments are used in practice with individuals who engage in food refusal and selectivity to identify foods that a child will readily consume before assessment and treatment. Traditional edible preference assessments may be challenging for children who engage in food refusal or selectivity as the child may not consume foods, but rather engage in inappropriate mealtime behavior simply due to the presence of food. Alternative modality preference assessments, such as pictorial, may offer benefits compared to traditional preference assessment formats (e.g., stimulus preference assessment and paired-stimulus preference assessment). The use of pictures may reduce any evocative effects of the presence of food and result in choice-making without inappropriate mealtime behavior. Experiment 1 assessed the correspondence between the hierarchies yielded from pictorial preference assessments (with and without access) to a standard edible preference assessment. Experiment 2 evaluated the accuracy of each preference assessment by presenting foods identified as preferred and non-preferred to determine if the child would accept them. Results suggested that pictorial preference assessments with access corresponded the most with the traditional edible preference assessment. Also, for one individual, the traditional preference assessment did not accurately identify foods that the participant would consume, while the pictorial preference assessment without access yielded a hierarchy.     

Polydipsia induced by intermittent delivery of salted liquid foods

Food-deprived rats given constant access to water were exposed to fixed-time presentations of soybean milk and diluted sweetened condensed cows' milk. In some conditions these liquid foods were adulterated with varying amounts of sodium chloride. Under a fixed-time 30-sec schedule of food delivery, little water was consumed when the food was soybean milk alone, or soybean milk with sodium chloride added in concentrations of .9, 1.8, or 3.6%. However, schedule-induced polydipsia appeared when soybean milk adulterated with 7.2 or 14.4% sodium chloride was delivered under this schedule. When soybean milk containing 7.2% sodium chloride was presented under fixed-time 15-, 30-, 60-, 120-, and 240-sec schedules, schedule-induced drinking increased with the fixed-time value from 15 to 120 seconds, and decreased at 240 seconds. Like soybean milk, diluted sweetened condensed milk delivered under fixed-time schedules of 30, 60, and 120 seconds failed to evoke schedule-induced polydipsia, but did so when adulterated with 7.2% sodium chloride. Drinking induced by salted liquid foods resembled the polydipsia engendered by spaced dry-food presentations in several ways, including temporal relation to food delivery, persistence within and across sections, sensitivity to interfood interval, and magnitude relative to intake evoked by bulk-food presentation.     

Dietary variety, energy regulation, and obesity

Increased variety in the food supply may contribute to the development and maintenance of obesity. Thirty-nine studies examining dietary variety, energy intake, and body composition are reviewed. Animal and human studies show that food consumption increases when there is more variety in a meal or diet and that greater dietary variety is associated with increased body weight and fat. A hypothesized mechanism for these findings is sensory-specific satiety, a phenomenon demonstrating greater reductions in hedonic ratings or intake of foods consumed compared with foods not consumed. Nineteen studies documenting change in preference, intake, and hedonic ratings of food after a food has been eaten to satiation in animals and humans are reviewed, and the theory of sensory-specific satiety is examined. The review concludes with the relevance of oral habituation theory as a unifying construct for the effects of variety and sensory-specific satiety, clinical implications of dietary variety and sensory-specific satiety on energy regulation, and suggestions for future research.     

空间距离与产品属性对消费者选择偏好的影响*

通过两个实验检验空间距离如何影响消费者选择偏好。实验一中,产品与消费者之间的空间距离不影响他们对不可匹配属性更优产品的偏好。实验二中,两种产品之间的空间距离与产品属性交互作用影响了消费者的选择偏好,使他们在两产品之间空间距离远时比近时更偏好不可匹配属性更优产品。两种不同类型的空间距离对消费者选择偏好的影响是不同的。强调两产品之间的空间距离远,会影响消费者在选择过程中对不可匹配属性的使用。