Resident rats’ aggression toward intruders

A study was performed in which attacks by four different types of “resident” rat (males housed with fertile females, males housed with sterile females, paired males, and isolated males) on six different types of intruder (isolated males, grouped males, castrated males, isolated females, grouped females, and ovariectomized females) were investigated. The objective was to study features of resident and intruder rats that would allow the designing of an aggression test that used a minimum of animals and produced a rapid behavioral response. In some combinations of residents and intruders, attack was generated within a 10-min test period. Isolated resident males attacked as much as males housed with females; however, paired rats showed only low incidences of attack. The fertility of the female partner did not influence the male’s aggressiveness. Most male attacks were directed towards like-sexed intruders. Only isolated males differentiated between the different treatment types of male intruder, attacking group-housed and castrated rats less intensely than isolates. Of the females, only those that were fertile produced significant amounts of attack behavior and almost exclusively attacked female intruders. Group-housed intruder females received more attacks than isolates. The results suggest optimal conditions for generating two models of attack behavior in the laboratory rat.     

Influence of shock controllability by dominant rats on subsequent attack and defensive behaviors toward colony intruders

Thirty colonies, each consisting of a female and two male adult albino rats, remained intact for an 8-week period. Naive conspecific intruders were then introduced into each colony for a 10-min test for 5 consecutive days. Videotapes of the tests were scored for aggressive and defensive behaviors. In every colony, aggression was greatest for a single alpha male. The alpha rats were randomly given one of three treatments: wheel-turn escape training, inescapable yoked shock, or restraint without shock. The alpha rats were then returned to their colonies and an intruder test was given 26 h later. Significant decreases in aggressive responses and increases in defensive behaviors occurred in the alpha yoked group but not in the other alpha groups. The nonalpha colony partners of the alpha yoked rats showed the opposite changes following the treatment. A final intruder test 72 h later revealed that the deficits in aggression of the alpha yoked group were still present but that the behaviors of most of the other groups were beginning to return to their respective pretreatment levels. These findings were discussed in terms of the concept of learned helplessness and alternative theoretical explanations.     

Signal duration and choosing between signaled and unsignaled reward

The effects of signal duration when choosing between signaled and unsignaled response-independent reinforcers were examined in two experiments. In Experiment 1, albino rats were given a choice between signaled and unsignaled food delivered on variable-time 60-sec schedules using a 20-sec signal. All subjects preferred the signaled schedule at a level comparable to that reported in an earlier study using a 5-sec signal. Experiment 2 presented six rats with a direct choice between a 5-sec and a 20-sec signal condition, and three rats with a choice between a 1.5-sec and a 5-sec signal duration. Subjects preferred the 20-sec signal over the 5-sec signal, but no pReference was found with the 1.5-sec vs. a 5-sec signal. Current theoretical views, such as delay reduction and behavioral competition, are considered.     

Visual and social determinants of shock-elicited aggressive responding in rats

Light and dark reared, social and isolate housed, male Long-Evans hooded rats were tested in bright and dim light for aggressive response to footshock. Test lighting and socialization main effects were significant, with greater fighting in dim light than in bright light and greater fighting by isolates than by socially housed animals. Test lighting interacted with prior visual experience and socialization interacted with past and present illumination variables. The results suggest an inhibitory effect of test illumination dependent upon prior social and visual experience.     

Training rats to discriminate between the odors of individual conspecifics

To determine the influence of genetic and microbiological factors in producing individually unique urine odors, we used a go/no-go operant task to assess the ability of eight male Long-Evans rats to discriminate between urine odors from the following pairs of male rats: (1) two outbred Long-Evans rats, (2) individual conventionally housed rats differing genetically only at the major histocompatibility complex (PVG vs. PVG.R1), (3) individual PVG versus PVG.R1 rats born by cesarean section and raised in germfree conditions, and (4) conventionally housed, genetically identical individuals of the PVG or PVG.R1 strains. Discriminable differences were present between the urine odors used in all four tasks. Analysis of the errors to a criterion of 85% correct discrimination responses revealed different learning patterns in each task. When bacteria were not present in genetically different rats (Task 3) and when bacteria were present but there were no genetic differences between rats (Task 4), the discrimination was the most difficult. The easiest discrimination involved the presence of bacteria and a genetic difference at the major histocompatibility complex (Task 2). These results indicate that, although bacteria are not necessary for the production of discriminable odor differences, they do influence the discriminability of the urine odors of rats.     

Competitive and noncompetitive rearing and shock-elicited aggression in the rat

Beginning at 21 days of age, rats were housed 10 per cage in a competitive environment (a large cage containing a single food and water source) or a noncompetitive environment (a large cage containing multiple food and water sources). At maturity, matched pairs of animals from within a single rearing cage were tested for shock-elicited fighting over five 100-trial sessions. In each of two experiments, animals reared in the noncompetitive environment displayed more aggressive behavior than animals reared in the competitive environment.     

The self-concept and aggressive behavior among elementary school children from two socioeconomic areas and two grade levels

An investigation was conducted to examine the relationship between a child's self-concept and the tendency to behave aggressively. Boys and girls (N=229) in eight classrooms (two third grades and two sixth grades from two different socioeconomic areas within the Provo, Utah, School District) were administered the Piers-Harris Children's Self-concept Scale and the Children's Action Tendency Scale. Correlation coefficients were computed, and analysis of variance tests were used to determine the nature of variable relationships. No overall correlational pattern was found among self-concept and aggression scores. The analysis of variance results revealed a significantly larger mean aggressiveness score among children with low self-concepts when compared to children with medium and high self-concepts. Girls, while less aggressive than boys, became more aggressive with age, while boys' aggressiveness scores declined. Implications of the results were discussed in terms of methods of behavior change utilized by school personnel.     

Social working memory: Memory for another rat's spatial choices can increase or decrease choice tendencies

In two experiments using a radial-arm maze, pairs of rats made choices among eight maze locations, each containing a large quantity of one of two food types. The choices made by 1 rat affected the choices made by the other rat. Under most conditions, visits by 1 rat increased the tendency of the other rat to subsequently choose that maze location. However, the effect depended on the quality of the food available in a particular location. When it was possible for the rats to observe each other on the maze arms and a rat had experienced that a location contained the less preferred food type, a previous visit to that location by the foraging partner decreased the tendency to visit that location. These effects are attributed to working memory for the spatial choices of another rat, and they indicate that memory produced by a rat’s own visit to a maze location is integrated with memory for the behavior of another rat to determine spatial choice     

Verbal aggression in sibling relationships

This study focused on verbal aggression in sibling relationships. The study examined the relationship between (a) verbal aggressiveness with satisfaction and interpersonal trust, (b) the relationship between teasing and verbal aggressiveness, (c) whether people more satisfied with their siblings report that receiving verbal aggression is more personally hurtful, and (d) whether sibling sex influenced verbal aggression in the relationship. Results support the destructiveness of verbal aggression in that verbal aggressiveness was negatively related to satisfaction and trust. Teasing was found to be positively related to being verbally aggressive. Sibling satisfaction was positively related to being hurt from receiving verbally aggressive messages. Results involving sex show that women are more satisfied and report using less verbal aggression and teasing than the other sibling dyads. Conclusions, future directions, and limitations are discussed.     

Chronic morphine drinking establishes morphine tolerance, but not addiction in Wistar rats

Objective： Some animal models apply morphine in the drinking water to generate addiction, but related reports are not free of conflicting results. Accordingly, this study aimed to figure out if chronic consumption of morphine in the drinking water can induce morphine addiction in Wistar rats. Methods： For 3 weeks, the animals received a daily morphine dose of 35 mg/kg by offering a calculated volume of sugar water （5% sucrose） with morphine （0. l mg/ml） to each rat; animals receiving just sugar water served as controls. Immediately after the treatment phase, the tail immersion test was used to check for morphine tolerance, and all animals were then kept on tap water for one week （withdrawal phase）. Afterwards, all rats were allowed to choose their drinking source by offering two bottles, containing sugar water without and with morphine, simultaneously for two days （preference phase）. Results： While the chronic consumption of morphine led to a reduction in body weight and to morphine tolerance, the morphine-treated Wistar rats did not show any preference for the opiate-containing sugar water. Conclusion： Body weight loss and tolerance do not reveal a condition of drug craving, and current animal models should be re-evaluated regarding their potential to establish morphine addicted animals.     

Do monkeys choose to choose?

Both empirical and anecdotal evidence supports the idea that choice is preferred by humans. Previous research has demonstrated that this preference extends to nonhuman animals, but it remains largely unknown whether animals will actively seek out or prefer opportunities to choose. Here we explored the issue of whether capuchin and rhesus monkeys choose to choose. We used a modified version of the SELECT task—a computer program in which monkeys can choose the order of completion of various psychomotor and cognitive tasks. In the present experiments, each trial began with a choice between two icons, one of which allowed the monkey to select the order of task completion, and the other of which led to the assignment of a task order by the computer. In either case, subjects still had to complete the same number of tasks and the same number of task trials. The tasks were relatively easy, and the monkeys responded correctly on most trials. Thus, global reinforcement rates were approximately equated across conditions. The only difference was whether the monkey chose the task order or it was assigned, thus isolating the act of choosing. Given sufficient experience with the task icons, all monkeys showed a significant preference for choice when the alternative was a randomly assigned order of tasks. To a lesser extent, some of the monkeys maintained a preference for choice over a preferred, but computer-assigned, task order that was yoked to their own previous choice selection. The results indicated that monkeys prefer to choose when all other aspects of the task are equated.     

Social interaction between drugged and undrugged rats

Social interaction between two rats placed in a hole-board apparatus was studied. The duration and frequency of active contact was higher for animals housed singly than for those housed in pairs, and for those tested with an unfamiliar rather than a familiar partner. Animals housed alone had a higher frequency and duration of passive contact, but the familiarity of the partner did not affect this measure. Chlorpromazine reduced the frequency of active contact but increased the frequency and duration of passive contact. When only one of the pair was drugged, both rats showed more frequent changes from one behavior to another, compared with pairs where both were in the same drug state. Animals housed alone showed the highest number of changes in behavior, and those tested with an unfamiliar partner showed a higher level than those tested with a familiar one.     

Concurrent schedules of wheel-running reinforcement: Choice between different durations of opportunity to run in rats

How do animals choose between opportunities to run of different durations? Are longer durations preferred over shorter durations because they permit a greater number of revolutions? Are shorter durations preferred because they engender higher rates of running? Will longer durations be chosen because running is less constrained? The present study reports on three experiments that attempted to address these questions. In the first experiment, five male Wistar rats chose between 10-sec and 50-sec opportunities to run on modified concurrent variable-interval (VI) schedules. Across conditions, the durations associated with the alternatives were reversed. Response, time, and reinforcer proportions did not vary from indifference. In a second experiment, eight female Long-Evans rats chose between opportunities to run of equal (30 sec) and unequal durations (10 sec and 50 sec) on concurrent variable-ratio (VR) schedules. As in Experiment 1, between presentations of equal duration conditions, 10-sec and 50-sec durations were reversed. Results showed that response, time, and reinforcer proportions on an alternative did not vary with reinforcer duration. In a third experiment, using concurrent VR schedules, durations were systematically varied to decrease the shorter duration toward 0 sec. As the shorter duration decreased, response, time, and reinforcer proportions shifted toward the longer duration. In summary, differences in durations of opportunities to run did not affect choice behavior in a manner consistent with the assumption that a longer reinforcer is a larger reinforcer.     

Behavioral field analysis in two strains of rats in a conditioned defensive burying paradigm

Two strains of rats (albino Wistar and hooded PVG/c) were exposed to a conditioned defensive burying paradigm that consisted of placing rats in a test chamber with bedding material on the floor, shocking them with a shock prod, and recording the time each rat spent in burying responses toward the prod. Various behaviors other than burying (freezing, grooming/paw licking) were observed by a time-sampling procedure during the control, conditioning, and extinction sessions, each of which was 15 min in duration. Wistar rats generally showed behavioral inhibition, as evidenced by less burying, lower exploratory and ambulatory behavior, and higher freezing behavior. PVG/c rats spent significantly more time engaged in burying and accumulated more bedding material in the conditioning session than did the Wistar rats. No significant differences between the two strains of rats were observed during the extinction session in terms of these measurements. The results indicate that Wistar rats have a greater tendency to freeze when coping with the noxious stimulus in a conditioned defensive burying paradigm, whereas the dominant coping style for PVG/c rats is defensive burying.     

Social responsiveness and physical space as determinants of agonistic behavior inBetta splendens

Two experiments examined the conditions under whichBetta agonistic responding occurs by manipulating physical space and the species and social responsiveness of an opponent. In Experiment 1, both the species (conspecific or nonconspecific) and the aggressiveness (aggressive or nonaggressive) of the opponent were manipulated. The results indicated that agonistic behavior was greater with both conspecifics and aggressive opponents. Experiment 2 examined the effects of physical space and social responsiveness of the opponent on intraspecific aggressive behavior. An inverse relationship was found between physical space and the number of attacks directed toward the opponent. The results of both experiments also indicated thatBetta tend to attack aggressive opponents more than nonaggressive ones. It is suggested thatBetta aggress either when the individual animal is threatened or when physical space is limited.     

Foraging on the radial-arm maze: Effects of altering the reward at a target location

Thirsty rats were trained to collect small water rewards from the end of each arm of an eight-arm radial maze. During these training trials and subsequent testing trials, the subjects were allowed to choose a maximum of eight arms. “Preference” for a target maze location was studied by noting when, in the sequence of eight choices, the target was selected. During testing, when one maze location was consistently devoid of water, rats decreased their preference for this arm over trials (Experiment 1). Similarly, rats that learned a saccharin-lithium association demonstrated lower preferences for a maze location that consistently held the conditioned saccharin solution. This was true for animals that received saccharin-lithium conditioning on the maze (Experiment 3A) and for animals conditioned to saccharin in a separate context (Experiment 3B). An increase in preference for a target maze location consistently containing a sweet chocolate milk solution was observed in animals that were water- and food-deprived (Experiment 2). These studies demonstrate that animals will modify their responses toward (preferences for) maze locations that predictably contain an altered reward.     

Effect of experience with a preferred food on consummatory responding for a less preferred food in goldfish

In two experiments with goldfish patterned after work with rats, consummatory responding for a less preferred food (adulterated with quinine) was measured in subjects that did or did not have previous experience of a preferred (unadulterated) food. The result in each case was not the negative contrast found in rats, but the opposite—more responding in subjects with experience of both foods. The experiments are in accord with a variety of others that have failed to show control of performance by remembered reward in goldfish.     

Differential effects of delay of reinforcement on acquisition of affective and instrumental responses

Thirsty rats were allowed to choose between a striped arm of a T-maze that contained water and a black arm that contained a saccharin solution. After each exposure to the saccharin solution, half of the animals received a lithium chloride injection 1 min later and half received the same injection 30 min later. Comparable saline injections at these same delays were given after each exposure to the striped, water, arm. The results from saccharin aversion, spatial aversion, and instrumental learning tests generally supported the hypothesis that delayed reinforcement has a substantially greater negative impact on the acquisition of an instrumental response than it has on affective conditioning.     

The determinants of random choice

The purpose of the present experiment was to describe a pattern of reinforcement sufficient to produce an unpredictable pattern of choice response by rats. On each trial two levers were inserted into an experimental chamber. If the reinforcement was always contingent upon single alternation (a simple pattern), Ss learned to alternate at significantly better than chance level; if reinforcement was contingent upon alternation on 50% of the trials (an insoluble pattern), Ss developed a position preference. To produce apparently random responding, the less preferred response (an alternation) was differentially reinforced on 75% of the trials. A simple stochastic model adequately described the results.