Effects of rearing condition,gender, and sexual experience on odor preferences and urine marking in Long-Evans rats

Two experiments investigated the effects of isolation rearing on olfactory communication in rats. In Experiment 1, there were significant rearing and gender effects on the time spent investigating conspecific odors, the preferences for these odors, and the amount of urine marking over these odors by sexually naive male and female rats. Experiment 2 found significant effects of rearing condition and sexual experience on the responses of male rats to conspecific odors. In general, isolation rearing increased the time spent investigating conspecific odors, but reduced the amount of urine marking over these odors and altered the odor preference scales. These results suggest that the responses of both male and female rats to the odors of conspecifics are modified by rearing experience. The importance of learning conspecific odor signals for the development of normal social behavior is discussed.     

Necessary and sufficient conditions for communication of diet preferences by Norway rats

Rats that (1) either ate a small sample of one or two foods (Diet A or Diet B) or interacted with a demonstrator that had eaten either Diet A or Diet B, (2) ate both Diets A and B in succession, and (3) were made ill preferred whichever of the two foods they or their respective demonstrators had eaten. Although eating a food and interacting with a demonstrator that had eaten that food were each sufficient to enhance preference for the food, eating particles of food clinging to the fur of a demonstrator was not necessary for enhancement of preference for the food that a demonstrator ate. Subjects exposed to demonstrators they could not physically contact still exhibited enhanced preference for the food that their demonstrator had eaten. The data were discussed as indicating that although smelling a diet, eating a diet, and interacting with a demonstrator that had eaten a diet can each enhance preference for that diet, it cannot be inferred that eating a food, smelling a food, and interacting with a demonstrator that has eaten a food each affect diet preference via the same process.     

Social learning and social transmission of foraging information in Norway rats (Rattus norvegicus)

Adult male Norway rats were tested in a first experiment to see whether foraging efficiency could be improved by social learning. Observers were placed in one of four conditions in which they were paired with demonstrators that either had or had not been previously trained to dig for buried carrot pieces, and in which the demonstrators either did or did not have carrot buried in the experimental enclosure. Observers in the group with trained demonstrators that did have carrot pieces buried in the experimental area during the observation period subsequently unearthed more buried carrot, did so more rapidly, and were generally more active than were the observers in the other three groups. In a second experiment, chains of transmission were established by allowing each observer to act as a demonstrator for the next naive observer. Enhanced levels of digging behavior were maintained across eight transmission episodes in three transmission groups relative to a no-transmission control group, the performance levels becoming stable after five transmission episodes at a level significantly above that of the control group. The study demonstrates that social learning and transmission mechanisms exist which might result in the diffusion of certain patterns of behavior through populations of Norway rats.     

A comparison of learned aversions to gustatory and exteroceptive cues in rats

The experiment provides a direct comparison of the ability of subjects (rats) to associate gustatory and exteroceptive stimuli with illness. Previous experiments which have made similar comparisons between gustatory and exteroceptive cues have suffered from certain methodological problems involving stimulus control and compounding. The present experiment utilized a between-subjects design wherein half of the subjects had an auditory cue associated with poisoning and half had a taste cue. In both cases, the other cue was present, but was not predictive of poisoning, The auditory cue, like the taste cue, occurred only during drinking. This comparison was made in both an immediate and a delayed poisoning situation. The experiment found that while subjects were able to quickly associate a taste cue with illness, they were unable to form a similar association between poisoning and the exteroceptive stimulus. Results also showed that subjects will fail to acquire a taste aversion to a novel and salient gustatory cue when that cue is followed by illness only 50% of the time. This latter effect was more pronounced in the delayed poisoning situation.     

Social and asocial cues about new food: Cue reliability influences intake in rats

Dietary generalists often treat new foods with caution and may rely on social cues to identify new foods that are safe to eat. However, not all generalists show the same degree of caution, nor do they all rely on social cues to the same extent. The cue reliability approach (CRA) attempts to account for this variation by quantifying the costs and benefits of sampling a new food for the first time. The experiments reported here tested predictions of the CRA, and the results suggested that rats eat more new food when asocial cues predict that new foods will prove more profitable than familiar foods. The experimental results also suggested that rats are more likely to seek out social cues when asocial cues are unreliable.     

Maze patrolling by rats with and without food reward

The effects of food reward on rats’ behavior in radial and Dashiell tunnel mazes were examined in two experiments. In the first, with animals at ad-lib body weights, food reward reduced speed of movement at the food locations, but did not affect the patterns of movement in either maze. Exploratory efficiency in the Dashiell maze was unaffected by food reward, and spontaneous patrolling of the radial maze by the nonrewarded animals was comparable to the behavior, reported by others, of rats running for food reward on elevated eight-arm mazes. In the second experiment, with subjects maintained at 80% of ad-lib body weights, there was some evidence for “winstay” learning: food-rewarded rats in the Dashiell maze were relatively more active near the food locations than were the nonrewarded animals, and more rewarded than nonrewarded rats revisited all food locations in the radial maze. Nonetheless, exploratory efficiency in the Dashiell maze was unaffected by food reward, as was patrolling efficiency in the radial maze, which was again comparable to that of rats on elevated mazes. The similarity in behavior of rewarded and nonrewarded animals in these mazes implies that the major determinant of their behavior, whether or not food reward is provided, is a spontaneous tendency to avoid places recently visited.     

Effects of food deprivation on learning and expression of flavor preferences conditioned by saccharin or sucrose

In four experiments, food deprivation was varied during conditioning and testing of conditioning of flavor preferences by sweeteners. Conditioned preferences for a flavor associated with a more concentrated solution were enhanced by increased deprivation in training whether sucrose or saccharin was used when rats consumed solutions freely during training. When consumption of solutions was controlled and higher deprivation levels were used, preference for the higher concentration of sucrose was still enhanced by increased deprivation in training, but this did not occur with saccharin. We suggest that deprivation may enhance the reinforcing value of sweetness only when calories increase along with sweetness. We also suggest that deprivation can enhance flavor preference learning by increasing consumption and thereby increasing exposure to the flavored solutions.     

Delays after eating: Effects on transmission of diet preferences and aversions

Previous studies have demonstrated that a naive rat (an observer), after interacting with a previously fed conspecific (a demonstrator), will exhibit an enhanced preference for the diet its demonstrator ate. Furthermore, observers poisoned after interacting with demonstrators exhibit an aversion to their respective demonstrators’ diets. In the present paper, we examined the effects, on transmission of information from demonstrator to observer, of introducing delays between the end of demonstrator feeding and initiation of demonstrator-observer interaction. We found that (1) for at least 4 h after ingestion, demonstrator rats emitted diet-related cues sufficient to alter observers’ subsequent diet preferences, and (2) diet-related cues emitted by demonstrators for 1 to 2 h after a meal were adequate conditional stimuli for aversion learning by their observers.     

Developmental differences in children's preferences for high- and low-arousing forms of contact stimulation.

In a 2-choice preference situation involving the availability of adult-administered cuddling versus tickling stimulation, overall preferences for cuddling steadily decreased across 4 groups of children from 3 to 7 years of age. This developmental decrease was most prevalent, for both boys and girls, when the contact agents were a female cuddler versus a male tickler. The reversal of these contact-sex roles (female tickler vs. male cuddler) did not affect the developmental preference for less cuddling stimulation of the 3 oldest groups of girls; however, the youngest girls now avoided male cuddlers, while the boys were found to prefer male cuddlers at all 4 age levels.     

Social influence on avoidance of dangerous stimuli by rats

Three experiments were conducted to determine whether a naive observer rat would avoid contact with a shock prod after watching a demonstrator rat contact, be shocked by, and defensively bury the prod. We found that observer rats took longer to contact prods that had delivered a shock to and been buried by a demonstrator rat than to contact prods that had not delivered shock and had not been buried. However, observer rats contacted prods buried by an unseen demonstrator rat or by an unseen experimenter with the same latencies as those for prods they had seen deliver shock to and be buried by a demonstrator rat. In large enclosures, subjects took 1–2 h longer to contact buried prods than to contact unburied prods. We conclude that alteration of the physical environment by individuals receiving noxious stimulation can significantly reduce the probability that conspecifics will contact the noxious stimulus. Observational learning per se, however, need not be involved.     

Social transmission of courtship behavior and mating preferences in brown-headed cowbirds,<Emphasis Type="Italic">Molothrus ater</Emphasis>

Studies of the social learning of courtship behaviors and mating preferences of brown-headed cowbirds (Molothrus ater) are reviewed. Earlier work has suggested that cowbirds from behaviorally distinct populations mate preferentially with others from the same population. Studies are described which indicate that patterns of courtship behavior that differ by population can be socially transmitted across generations are described. Social background affects male songs, female preferences for males as mates, and courtship interactions between females and males. Thus, social traditions influence mating decisions and may, ultimately, impact reproductive success in this species. Recent work on possible social mechanisms involved in the ontogeny of courtship behavior is described. The implications of these findings are discussed, and future research directions are suggested.     

A sociometric investigation of sex and race peer preferences among deaf adolescents

This study investigated sex and race peer preferences among adolescent deaf students. Sociometric ratings were obtained and analyzed for possible preferences. A marked peer preference for female students by both male and female students was found. In examining racial preferences, I found that white students rated same-race students higher than they rated minority students. Based on the data and analyses, the investigator found race to be secondary to sex in peer preferences among deaf adolescents. These findings are consistent with the sociometric literature on hearing adolescents.     

Absence of blocking,overshadowing, and latent inhibition in social enhancement of food preferences

A rat’s preference for food of a given flavor can be substantially enhanced by allowing it to interact with a conspecificdemonstrator that has recently eaten food of that flavor. The heuristic value of treating such socially induced enhancement of flavor preference as an instance of Pavlovian conditioning was examined in three experiments. Conceiving of the smell of the food as a conditional stimulus and other cues emanating from the demonstrator rat as an unconditional stimulus, we determined whether each of three common Pavlovian phenomena-blocking, overshadowing, and latent inhibition-would occur. Using experimental parameters that readily produce socially induced enhancement of flavor preference, none of the three Pavlovian phenomena were found.     

Acquisition of schedule-induced polydipsia by rats in proximity to upcoming food delivery

Food-deprived rats that receive intermittent delivery of small amounts of food develop excessive drinking--specifically, schedule-induced polydipsia (SIP). A main characteristic of SIP is its occurrence at the beginning of interfood intervals. The purpose of this study was to demonstrate that SIP can be developed toward the end of interfood intervals, in closer proximity to upcoming than to preceding food delivery. In Experiment 1, two groups were exposed to a fixed-time (FT) 30-sec food schedule with water available during the first or the last 15 sec of each interfood interval. Two additional groups, which had access to water throughout, were exposed to FT 30-sec or FT 15-sec schedules of food presentation. The FT 30-sec group with free access to water developed the highest level of intake; similar and intermediate levels were induced in all the remaining groups. In Experiment 2, three groups of rats were exposed to an FT 90-sec food schedule with water available during the first, the second, or the last 30 sec of each interfood interval. One additional group with access to water throughout was exposed to the FT 90-sec schedule of food presentation. The group with free access to water developed a higher level of consumption than did the other groups, but by the end of training none of the four groups showed statistical differences in polydipsic drinking. Results show that adjunctive drinking can be developed in proximity to upcoming food delivery even with long interfood intervals.     

Social processes and outcomes of in-school contact between deaf and hearing peers

Studies of social processes and outcomes of the placement of deaf students with hearing peers cannot be easily summarized, but can be grouped into a least four major categories of focus: social skills, interaction and participation, sociometric status and acceptance, and affective functioning. We review 33 studies available since 1980 in which a mainstreamed or included deaf sample was compared to another group. Studies indicated (1) that hearing students were more socially mature than deaf students in public schools, (2) that deaf students interacted with deaf classmates more than hearing ones, (3) that deaf students were somewhat accepted by their hearing classmates, and (4) that self-esteem was not related to extent of mainstreaming. There was a tendency for studies to use observational methods with very young children, teacher evaluations with middle school children, and questionnaires with older children. Three major areas of methodology limit general conclusions: samples, measurements of variables, and experimental manipulations. The reviewed studies provide a basis for understanding the social processes and outcomes in these placement situations; however, it is not possible to make broad generalizations about effects of placement.     

Social influences on the identification of toxic foods by Norway rats

In the present experiments, a naive “observer” rat first interacted with a “demonstrator” rat previously fed a diet unfamiliar to the observer. The observer then sampled two unfamiliar diets, one of which was the diet its demonstrator had eaten. The observer was then injected with LiCl and, following recovery from toxicosis, was offered a choice between the two diets it sampled prior to toxicosis induction. It was found that: (1) each observer rat formed an aversion to whichever diet its demonstrator had not eaten, (2) effects of demonstrators on aversion learning by observers were present even if there was a 7- or 8-day delay between interaction of a demonstrator and observer and diet sampling by the observer, and (3) observers interacting with 3 demonstrators, each fed a different diet, subsequently exhibited a reduced tendency to form an aversion to each of the diets eaten by their demonstrators. Taken together, the results indicate that information acquired from conspecifics as to the diets they have eaten can play an important role in determining the foods to which otherwise naive rats will learn aversions.     

Effects of CSs for food and water upon rats barpressing for different magnitudes of food reinforcement

Forty-eight albino rats were first exposed to randomly intermixed, noncontingent presentations of one pellet, six pellets, and water. For each of three groups, a CS+ was paired with one of the reinforcers, while the other two reinforcers and a CS? were presented alone. Then half the subjects experienced a six-pellet reward and half experienced a one-pellet reward for leverpresses during a light S^D. Finally, on test trials, the CS+ or CS? was compounded with the light. Latencies on test trials indicated that responding for the one-pellet reward was significantly more disrupted by a CS+ for six pellets than by the CS+ for one pellet or the CS+ for water. Responding for the six-pellet reward was disrupted by the CS+ for one pellet somewhat more than by the CS+ for six pellets or water, but not significantly so. This pattern of results is partially consistent with an associative model of transfer and appears to contradict a motivational account of such effects.