Effects of social and asocial learning on longevity of food-preference traditions

The influence of both social and asocial factors on the stability of a socially learned tradition of food preference was explored in colonies of domesticated Norway rats, Rattus norvegicusWe trained members of 'founding colonies' of rats to avoid eating a distinctively flavoured food and then introduced them into enclosures where they were offered a choice between the food they had learned to avoid and a familiar, safe food. We then monitored the food preferences of these colonies while we gradually replaced founding members with naive subjects. Traditions of food preference were more stable across generations of replacements: (1) in colonies that had food available 2 h/day than in colonies that had food available 24 h/day (experiment 1), (2) when replacement subjects each resided in their respective colonies for 2 days rather than for 4 days before themselves being replaced (experiments 2 and 3) and (3) when founding members of colonies had learned to avoid a relatively palatable diet (experiment 4). The results of the first four experiments were consistent with the view that opportunities to learn asocially to eat a food other than that preferred by one's fellows reduced the stability of a food preference as it was transmitted across generations. We also found that introducing a naive individual into a tradition-bearing colony reduced its rate of acquiring a food preference other than that of the colony it joined (experiment 5). The interactive effects of social and asocial learning on the stability of food preference traditions in Norway rats was discussed.     

Utilization by Norway rats (R. norvegicus) of multiple messages concerning distant foods.

Three experiments with 360 Long-Evans rats examined whether an individual rat remaining in its burrow and interacting with a succession of conspecifics returning from foraging trips could collect information concerning the range of foods the returning foragers have exploited. Results indicate that a naive S interacting with a series of conspecifics, each of which had previously eaten a distinctive diet, (a) extracted information from each conspecific sufficient to permit identification of the diet that individual had eaten, (b) distinctively encoded that information, (c) stored it for at least 12 hrs, and (d) retrieved and used the stored information to orient its own feeding behavior. Results extend the findings of the author and S. W. Wigmore (1983) of a capacity of rats to extract sufficient olfactory information from an individual conspecific to permit identification of the diet that individual has previously eaten. (7 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

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. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

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 2 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. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

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

48 naive female Long-Evans rats (observers) interacted with 2 conspecifics (demonstrators [n?=?96]) that had recently eaten a diet unfamiliar to the observer; ate 2 unfamiliar foods in succession, one of which was the food its demonstrators had eaten; suffered toxicosis; and were offered a simultaneous choice between the 2 diets they had eaten prior to toxicosis induction. During the choice test, observers exhibited an aversion to that diet their respective demonstrators had not eaten. It is suggested 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 and 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. (12 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Predatory attack by rats: Its relationship to feeding and type of prey.

Investigated mouse killing behavior in 5 experiments with male Long-Evans rats (N = 233). Hunger potentiated mouse killing by naive Ss, but not by Ss familiarized with mice before and during food deprivation. Once Ss had been made hungry, mouse killing was unaffected by increasing or decreasing severity of food deprivation or by time of testing with respect to a regular feeding hour. Ss fed either dead mice, powdered chow, or hard pellets while on cyclic food deprivation were about equally likely to kill, showing that hunger does not indirectly potentiate killing by increasing practice of responses like pouncing and biting. Whether hungry or not, killers were likely to eat their prey, whereas nonkillers were unlikely to eat the same prey. Ss killed 12-14 day-old rat pups as often as they killed mice, but killed weanling rat pups less often. Findings question several common notions regarding predatory aggression. (26 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

"Social influences on the selection of a protein-sufficient diet by Norway rats (Rattus norvegicus)": Correction to Beck and Galef (1989).

Reports an error in "Social influences on the selection of a protein-sufficient diet by Norway rats (Rattus norvegicus)" by Matthew Beck and Bennett G. Galef (Journal of Comparative Psychology, 1989[Jun], Vol 103[2], 132-139). There was a misstatement. On page 137, second column, second paragraph, the sentence that begins on line 7 ought to read as follows: Protected t tests revealed that subjects in the Different Food-Same Place Group gained a significantly smaller percentage of body weight than did subjects in each of the other two groups (LSD = .67, both ps 1989-31944-001.) Investigated effects of interactions between naive and knowledgeable rats (Rattus norvegicus) on selection of a nutritionally adequate diet by the naive. We found that during a 7-day test, isolated rats choosing among 4 foods, 3 of which were protein-deficient and 1 of which was protein-rich, failed to learn to prefer the protein-rich diet and lost weight. Conversely, those rats that interacted with conspecifics trained to eat the protein-rich diet developed a strong preference for that diet and thrived. The authors also found that Ss were more strongly influenced in their diet selection by the flavor of the foods eaten by conspecifics than by the locations where conspecifics fed. The results suggest that social influence may be important in development of adaptive patterns of diet choice by rats (or other dietary generalists) that need to find nutritionally adequate diets in demanding environments. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Response acquisition with delayed reinforcement.

Discrete responses of experimentally naive, food-deprived White Carneaux pigeons (key pecks) or Sprague-Dawley rats (bar or omnidirectional lever presses) initiated unsignaled delay periods that terminated with food delivery. Each subject first was trained to eat from the food source, but no attempt was made to shape or to otherwise train the response. In both species, the response developed and was maintained. Control procedures excluded the simple passage of time, response elicitation or induction by food presentation, type of operandum, food delivery device location, and adventitious immediate reinforcement of responding as the basis for the effects. Results revealed that neither training nor immediate reinforcement is necessary to establish new behavior. The conditions that give rise to both the first and second response are discussed, and the results are related to other studies of the delay of reinforcement and to explanations of behavior based on contingency or correlation and contiguity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of food deprivation on hunger motivation in golden hamsters (Mesocricetus auratus).

Unlike most other laboratory animals, golden hamsters do not typically increase their food intake following periods of food shortage. It is possible that the hamster feeding system may not be programmed to respond to the metabolic consequences of deprivation; expressed in motivational terms, deprived hamsters would not be hungrier than usual and therefore would not eat more than usual. However, because food consumption is influenced both by hunger motivation and by the motivation to stop eating, the amount of food eaten is not necessarily the best measure of hunger motivation. Four experiments were conducted, revealing that acute food deprivation has significant effects on latency to eat, speed of eating, consumption of a quinine-adulterated diet, open-field activity, and persistence of performance of an instrumental response during extinction. These results constitute convergent evidence that food deprivation increases the hunger motivation of golden hamsters, although deprivation does not lead to increases in the total food intake. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Social cues influence foraging in dwarf hamsters (Phodopus campbelli).

In 2 experiments, dwarf hamsters (Phodopus campbelli) were trained to find palatable foods in an open field. The location of each food patch remained the same throughout each experiment, and only 1 food was available per day. Once subjects had been trained to find each food in its unique location, they progressed to a testing phase in which subjects’ mates were allowed to eat and hoard the food that was available in the open field each day. The foods that subjects’ mates brought back to the home cages then served as discriminative stimuli signaling which food could be obtained in the open field. Subjects generally approached the patch containing the food hoarded by their mates, suggesting that dwarf hamster burrows could function as information centers. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Social influences on the selection of a protein-sufficient diet by Norway rats (Rattus norvegicus).

[Correction Notice: An erratum for this article was reported in Vol 104(2) of Journal of Comparative Psychology (see record 2008-10625-001). There was a misstatement. On page 137, second column, second paragraph, the sentence that begins on line 7 ought to read as follows: Protected t tests revealed that subjects in the Different Food-Same Place Group gained a significantly smaller percentage of body weight than did subjects in each of the other two groups (LSD = .67, both ps Rattus norvegicus) on selection of a nutritionally adequate diet by the naive. We found that during a 7-day test, isolated rats choosing among 4 foods, 3 of which were protein-deficient and 1 of which was protein-rich, failed to learn to prefer the protein-rich diet and lost weight. Conversely, those rats that interacted with conspecifics trained to eat the protein-rich diet developed a strong preference for that diet and thrived. The authors also found that Ss were more strongly influenced in their diet selection by the flavor of the foods eaten by conspecifics than by the locations where conspecifics fed. The results suggest that social influence may be important in development of adaptive patterns of diet choice by rats (or other dietary generalists) that need to find nutritionally adequate diets in demanding environments. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

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

Four studies examined whether socially transmitted diet preference could counteract the effects of a learned aversion, a palatability-based diet preference, a polyethylene glycol 20,000-induced sodium appetite, and a handling time-induced dietary preference. Results indicate that (a) Ss poisoned after eating a novel diet ate substantial amounts of the averted diet following interaction with conspecifics that had eaten the averted diet. (b) Following interaction with conspecifics that had eaten an unpalatable diet, Ss offered a choice between palatable and unpalatable diets ate more than twice as much unpalatable diet as did controls lacking social experience. (c) Sodium-deficient Ss 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 controls lacking social experience. (d) Ss offered a choice between isocaloric, roughly equipalatable foods with long and short handling times chose the food having the longer handling time after interacting with conspecifics eating that food. It is suggested that social influence is a major factor in guiding diet selection by rats. (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Piloting and dead reckoning dissociated by fimbria-fornix lesions in a rat food carrying task

Control rats and rats with fimbria-fornix (FF) lesions were tested in a foraging task that required that they emerge from either a visible or hidden home base onto an open field to hunt for food pellets, which they then carry back to the home base to eat. Once they were proficient at returning to a location, they and the home base were moved so that they emerged to forage from a new starting position. When the location of a visible home base was moved, both groups of rats learned to make accurate returns. When the location of a hidden home base was moved, control rats first carried the food to the old location and then accurately returned to the new location as their second choice. Thus, as early as a first 'reversal' trial, they displayed spatial memory for both locations while the FF rats perseverated in returning to the old location. In returning to familiar start points, the rats may use distal visual (allothetic) cues and piloting, while when returning to new start points they may use self-movement (ideothetic) cues and dead reckoning. That FF lesions dissociated the two kinds of navigation suggests a role for the hippocampus in navigation based on ideothetic cues.     

Social influences on feeding site selection by Burmese fowl (Gallus gallus).

Naive, adolescent Burmese red jungle fowl (Gallus gallus spadiceus) observed trained conspecifics feeding in a large enclosure. When tested 48 hrs later, observers exhibited significantly enhanced preferences both for the type of foraging site and for the area in the enclosure where they had observed conspecifics foraging successfully. Such delayed influences of observations of foraging success on the orientation of feeding by an observer can be explained as an instance of stimulus enhancement (K. W. Spence, 1937) but not as an example of local enhancement (W. H. Thorpe, 1963). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Social influences on rats' (Rattus norvegicus) preferences for flavored foods, scented nest materials, and odors associated with harborage sites: are flavored food special?

We undertook in several experiments to determine whether the enhanced preference an observer rat (Rattus norvegicus) exhibits for a food after it interacts with a demonstrator rat fed that food reflects a general enhancement of the observer's preference for objects smelling like the food its demonstrator ate or results from a change in olfactory preference specific to foods. After an observer rat interacted with a demonstrator, it exhibited an enhanced preference for either cinnamon- or cocoa-flavored food that its demonstrator had eaten, but no change in its preference for similarly scented nest materials or nest boxes. The results are not consistent with the view that social influence on food choices of rats reflects a general enhancement of rats' preferences for objects bearing scents previously experienced while interacting with conspecifics. Rather, social influences on odor preferences appear to be restricted to scented foods.     

Theoretical note on the moral development of rats (Rattus norvegicus).

Rats trained to eat a fixed number of food items from a larger array began to consume additional pieces of food when the experimenter was no longer available to punish errors (Davis & Bradford, 1988). When such departures from "correct" behavior are viewed in terms of Kohlberg's (1976) schema of moral development, it appears that rats are functioning in the Preconventional mode. However, it may be inappropriate to view rats as a morally deficient species. Although notions of morality need not be confined to human behavior, numerous problems are associated with comparing the residual effects of punishment ("resistance to temptation") both within or between species. The results of such comparisons and their implications for morality must be evaluated with utmost caution. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Social influences on rats' (Rattus norvegicus) preferences for flavored foods, scented nest materials, and odors associated with harborage sites: Are flavored foods special?

Undertook in several experiments to determine whether the enhanced preference an observer rat (Rattus norvegicus) exhibits for a food after it interacts with a demonstrator rat fed that food reflects a general enhancement of the observer's preference for objects smelling like the food its demonstrator ate or results from a change in olfactory preference specific to foods. After an observer rat interacted with a demonstrator, it exhibited an enhanced preference for either cinnamon- or cocoa-flavored food that its demonstrator had eaten, but no change in its preference for similarly scented nest materials or nest boxes. The results are not consistent with the view that social influence on food choices of rats reflects a general enhancement of rats' preferences for objects bearing scents previously experienced while interacting with conspecifics. Rather, social influences on odor preferences appear to be restricted to scented foods. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Absence of satiety during sham feeding in the rat.

In 2 experiments, a total of 9 Sprague-Dawley rats with chronic gastric fistulas were trained to eat a liquid diet. Results indicate that when the fistulas were opened for the first time, Ss sham-fed eagerly and did not become satiated during test periods of 2 or 7.5 hrs. This sustained hyperphagia occurred after long (17 hrs) or short (10-30 min) intermeal intervals. The experience of sustained hyperphagia when gastric fistulas were open did not affect intake of the same diet on the next day when gastric fistulas were closed. When taste and other oropharyngeal stimuli acted alone during sham feeding, they did not elicit satiety. It is concluded that the occurrence of satiety in rats is critically dependent on an inhibitory reflex elicited by ingested food accumulating in the stomach and moving through the small intestine. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differential effect of lipopolysaccharide on food hoarding behavior and food consumption in rats

Experimental studies assessing the suppressing effect of lipopolysaccharide (LPS) on feeding behavior have focused exclusively on the ingestive component of this behaviour without taking into account its appetitive component. The appetitive sequence of feeding behavior regroups activities animals engage in to gain access to food without necessarily eating it. The objective of the present study was to compare the effects of LPS on food intake and food hoarding. Rats were given the possibility to access food during a 30-min daily session in an apparatus consisting of a cage connected to an alley with free food at its end. Subjects were tested under different motivational levels for food hoarding: a first group (FS) received a food supplement to maintain stable body weight while a second group (noFS) did not receive such a supplement. LPS (250 micrograms/kg i.p.) dramatically decreased total food intake in rats from both groups whereas food hoarding was much less affected in LPS-treated rats from the noFS group. This expression of a still salient secondary motivation in LPS-treated rats which did not receive any food supplement can be interpreted to suggest the expression of an anticipatory feeding behavior along with a reduced immediate appetite. In addition, LPS had no effect, in rats from the noFS group, on the amount of food eaten after transport to the refuge. LPS-treated animals still appear to be able to adjust their defensive behavioral strategies with regard to their needs and capacities. These findings support the adaptive value of the behavioral changes displayed by LPS-treated animals.     

The timing of food availability affects growth in chicks

Three experiments challenged the ability of domestic chicks to grow normally by differentially restricting when and for how long food was available. In Experiments 1 and 2, food was available for six 1-hr, three 2-hr, two 3-hr, or one 6-hr (a.m., p.m.) periods/day over the first 3 posthatch weeks. Control groups received continuous access to food. In Experiment 3, different amounts of light surrounded the 6-hr feeding period. In Experiments 2 and 3, chicks composed their own diets from separate sources high in protein or carbohydrate. Except for the single 6-hr meal preceding dark, large meals at other times of day impaired growth--primarily because chicks consumed insufficient dietary protein and ate less earlier in the light phase. We conclude that both the amount eaten and the proportion of the diet consumed as protein at given times of the day are phylogenetically acquired strategies that fit the omnivorous, diurnal chicken to its niche, independent of its momentary requirements, and appear early in development.