Relationship between shock-induced aggression and other laboratory tests of agonistic behavior in rats

The utility of the shock-induced aggression paradigm has been questioned in recent years. Studies were reviewed that demonstrated similar effects of independent variables on shock-induced, resident-intruder, and home-cage aggressive behavior. Correlations between naturally occurring aggression and shock-induced aggression, studies showing the influence of naturally occurring agonistic experience on shock-induced aggression, and the effects of shock-induced aggressive experience on resident-intruder behavior were also reviewed. It was argued that continued research into shock-induced aggression and its relationship to other laboratory paradigms would be useful, and that abandonment of the paradigm at this time would be premature.     

The offensive nature of maternal aggression in mice: Effects of fluprazine hydrochloride

The phenylpiperazine fluprazine hydrochloride was used to test the hypothesis that maternal aggression in laboratory mice reflects offensive motivation. Lactating females (n = 8 per condition) tested for aggression following drug treatment (1.0 mg/kg and 5.0 mg/kg of fluprasine) were significantly less aggressive than saline controls according to all measures used. The findings support the hypothesis that maternal aggression is offensive in nature, and provide no evidence that maternal attack is a mixture of offensive and defensive tendencies.     

Fear and aggression in the rat

The effect of fear on two types of aggression in rats was investigated by adding a cat stimulus to a colony in which the dominant male was attacking an intruder (offensive aggression), or, to a tube test situation in which defensive biting was measured before and during tail shock. The cat completely abolished offense in the colony; when the cat was presented and removed before a strange rat was placed in the colony, attack on the intruder was also reduced. In contrast, defensive biting was unchanged or even slightly potentiated by the presence of the cat, demonstrating a separation of the effects of fear on offensive and defensive aggression.     

Schedule-induced aggression in humans and animals: A comparative parametric review

Studies of animal and human aggression induced by schedules of reinforcement are reviewed. Parameters reviewed include: schedules, characteristics of induced aggression, subject variables, target variables, and the control or modification of schedule-induced aggression. With the exception of temporal locus of schedule-induced attack, the parameters identified with animal subjects are remarkably similar to those identified with human subjects.     

On the dual nature of maternal aggression in rats

Presentation of a natural predator, a cat, was used to differentiate elements of maternal attack by female rats on a male intruder. Following exposure (without direct physical contact) of post-partum females to a cat or to a toy stuffed cat (control group), the females were replaced in their home cages and presented with a male intruder rat. Cat exposure reliably decreased lateral attack to the intruder, as well as locomotion, but had no effect on either jump attack or an upright defensive posture (boxing). Since predator exposure produces a somewhat durable increase in defense, along with inhibition of nondefensive behavior, these results suggest that maternal aggression represents a mixture of offensive, usually related to competition, and defensive (protective) behaviors. The results indicate that maternal aggression, as a parental care behavior, appears to be at least partially resistant to fear. © 1996 Wiley-Liss, Inc.     

Relationship between mousekilling and conspecific aggression in the male rat

In order to investigate the relationships between mousekilling and conspecific aggression, behavioral variables of killer and nonkiller rats were compared in a “resident-intruder” paradigm, in resident as well as in intruder animals. The occurrence of offensive items (offensive sideways, attack) was significantly higher in killer rats when they were residents; their corresponding opponents displayed more defensive behaviors. No significant difference in aggressive behaviors was noted when the comparison was done in the intruders. These results and those of previous studies suggest that there is a correlation between mousekilling and intraspecific offensive behaviors. Some similarities in the situations where both behaviors are elicited–eg, introduction of an unfamiliar intruder into a familiar environment–may contribute to the existence of such a correlation and the possibility of common mechanisms underlying both behaviors is discussed.     

Ethical recommendations for workers on aggression and predation in animals

The recommendations of a recent workshop (Leiden, Netherlands, November 17–18, 1990) concerning the use of animals in research on aggression and predation are listed. Major considerations included the grade of organisation/level of development of the organism, the duration and intensity of the interaction, post-treatment factors, the number of animals and reuse of animals. It is hoped that the recommendations will help scientists working in these areas to consider the increasingly important ethical dimension.     

Prenatal sex hormones and human aggression: A review,and new data on progestogen effects

We review data on aggression from psychological studies of offspring from two categories of abnormal prenatal sex hormone conditions: 1) endocrine disorders, and 2) hormone treatment during pregnancy. Both sources yield trends and some significant findings that are in line with the animal research based expectations of a positive androgen effect on the development of aggressive behavior. However, the available studies have many methodological weaknesses, and the results are not strong and open to interpretations by factors other than prenatal hormones. Potential modes of prenatal sex hormone effects are also discussed. In the second part, we present data on 13 boys and 15 girls who had been exposed to medroxyprogesterone acetate (MPA) in utero and on 28 closely pair-matched controls. The double-blind follow-up examination at age 9 to 14 years included questionnaires, half-structured interviews with mother and child separately, and a battery of psychological tests. Interviews were tape-recorded and rated by two independent raters. The results show weak but consistent differences, with the MPA-exposed subjects being lower in self- or mother-reported aggression than the controls. The results cannot be accounted for by differences in aggression-related rearing styles. However, the influence of pregnancy pathology cannot be totally excluded. We conclude that the available data are compatible with the hypothesis that prenatal sex hormones influence the development of human aggressive behavior. More sophisticated research studies are needed, however, to demonstrate hormonal effects and their mechanism of action in a reliable and valid fashion.     

Psychopathy and aggression: Examining the role of psychopathy factors in predicting laboratory aggression under hostile and instrumental conditions

Psychopathy is a problematic configuration of traits and behaviors that is consistently correlated with aggressive, criminal behavior. Studies have suggested that psychopathy is composed of related but distinct factors that manifest divergent relations with a host of constructs including aggression. In the current study, we used a sample of 126 men to examine whether these psychopathy factors are differentially related to aggression manifested in two conditions (instrumental and hostile/reactive aggression) of a laboratory aggression paradigm. Traits related to an antagonistic interpersonal style and emotional detachment (i.e., Factor 1) were related to aggression in both conditions whereas traits related to negative emotionality, impulsivity, and an antagonistic style (i.e., Factor 2) were related to aggression only in the hostile/reactive condition. Potential explanations for these findings are put forth.     

Maternal and paternal parenting styles associated with relational aggression in children and adolescents: A conceptual analysis and meta-analytic review

How does parenting affect relational aggression in children? The goal of the present series of meta-analyses based on 48 studies (28,097 children) was to analyze and integrate the findings on the associations between various types of parenting behaviors and relational aggression, and to identify potential substantive and methodological factors that may moderate these associations. To distinguish between different parenting strategies, experts sorted the parenting measures used in the studies into 10 groups. Results of a multiple correspondence analysis revealed four separate clusters: Positive parenting, psychologically controlling parenting, negative/harsh parenting, and uninvolved parenting. The meta-analyses demonstrated that more positive parenting was associated with less relational aggression (combined effect sizes r = −.06, p < .05, for mothers, r = −.08, p < .01, for fathers). More harsh parenting (combined effect sizes r = .11, p < .01, for mothers, r = .12, p < .01, for fathers) and more uninvolved parenting (combined effect sizes r = .07, p < .01, for mothers, absent for fathers) were associated with increased relational aggression. Paternal psychologically controlling parenting was positively related to relational aggression (r = .05, p < .01), whereas maternal psychologically controlling parenting was not (combined effect sizes r = .04, p = .09). The effect of several moderators is discussed. The findings of this study suggest that dimensions of positive and negative parenting behaviors of mothers and fathers are associated with children’s relational aggression and that these associations are – in case of fathers – contingent upon a number of sampling and procedural characteristics.     

攻击性和自尊关系的元分析

以往攻击性和自尊之间关系的研究结论存在很大分歧。为了综合以往研究,明确两者之间的整体关系,分析造成分歧的原因,81项原始研究进入了元分析。结果显示:(1)攻击性和自尊呈中等程度的负相关。(2)自尊的不同结构与不同类型的攻击性呈现不同的相关模式。攻击性与外显自尊和内隐自尊呈负相关;攻击性与自尊稳定性和相倚性呈正相关(3)年级和攻击性量表类型的调节效应显著。攻击性与高自尊异质性之间的关系是将来研究的重点。     

Ethological analysis of neuropeptides and psychotropic drugs: Effects on intraspecies aggression and sociability of isolated mice

The experiments on mice (under the condition of agonistic interactions) have shown increases and decreases in certain forms of species-specific behavior (aggression, defense, sociability) when synthetic peptides and psychotropic drugs were administered. MIF-1, TRH, and LH-RH (acute injections) enhance aggression in isolated mice while somatostatin reduces it. MIF–1 antagonizes the antiaggressive effects of haloperidol, muscimol, and morphine. ACTH 1–24 counteracts the action of diaze-pam on attacks and threats. Somatostatin reduces both aggression and sociability and that effect may be potentiated by diazepam. Neo-endorphin injected together with diazepam reduces aggression and enhances sociability. A combination of synthetic neuropeptides and well known psychotropic drugs (neuroleptics, tranquil-izers, and others) may be more effective for the control of aggression and sociability than the psychotropic drugs employed alone.     

Androgens and aggression in man: A controlled case study

A controlled case study is reported of the behavioural effects of androgen treatment in an institutionalised hypogonadal mentally retarded male patient. This man was previously treated with intramuscular depot injections of testosterone esters; however, treatment had to be stopped as the androgens allegedly precipitated frequent bouts of violent behaviour. Using ratings of behaviour by hostel staff, replacement therapy was restarted using the new orally effective androgen, testosterone undecanoate (TU). Gradually increasing the replacement dose of TU in a double-blind fashion resulted in no stimulatory effect on aggressive behaviour. Possible reasons for the differential behavioural response to the two androgen preparations are presented.     

Aversive potency of urine from dominant and subordinate male laboratory mice (Mus musculus): Resolution of a conflict

The present study assessed the aversive potency of urine collected from male albino mice that had been clearly identified as dominants/winners or subordinates/losers of paired aggression tests and then housed either individually or in a quasi-paired situation in which only a wire-mesh divider separated the two mice. This divider permitted constant visual, olfactory, auditory, and some tactile contact. The responses of individually tested, group-housed males were recorded when half of the substrate in a test box was treated with either water or one of the four urine types; the other half remained untreated. Significant preferences for the untreated half were found when the urine of winners or losers housed in individual metabolism cages or that of pair-housed dominants was used as the test stimulus. On the other hand, neither water nor the urine of cohabiting subordinate males was avoided. The present findings confirmed our earlier reports that the urine of dominant male mice was aversive, whereas that of their cohabiting subordinate partners was not. They also identified Sawyer's [1978] procedure of housing winners and losers in individual cages, with the consequent interruption of social contact as the likely reason for his failure to replicate our reports that subordinate male urine lacked aversive properties. The territorial implications of the aversive factor and other urinary signals are discussed.     

Maternal aggression in rats: Changes over pregnancy and lactation in a sprague-dawley strain

Maternal aggression in a Sprague-Dawley strain of laboratory rat (Charles River CD) was explored from Day 1 after mating on Day 0 through Day 24 of lactation (L0-L24). Aggression toward unfamiliar male “intruders” during 10-min tests was low among nonpregnant, nonlactating females and during the first 10 days of gestation. Frequency of attack on intruders increased moderately but significantly by Gestation Day 16 (G16; Experiment 1) or G21 (Experiment 2), a prepartum phenomenon not previously reported in laboratory rats. Levels of aggression were highest, however, during the first 9 days of lactation, when attacks averaged more than 6 per 10-min session. Attacks declined sharply in frequency after L14 and by L24 did not exceed levels observed among nonpregnant females. Experiment 3 examined the importance of the test site (home cage with nest and pups, if any, vs unfamiliar cage without nest or pups) to agonistic behavior associated with pregnancy and lactation. Late pregnant females tested in a novel cage were not aggressive; however, females tested shortly after delivering their pups were highly aggressive, averaging over four attacks per 5-min session. In novel cage tests frequency of attack remained high through L4 but declined significantly by L7. These data are consistent with the hypothesis that maternal aggression at its onset is primarily under hormonal control, but becomes increasingly dependent upon external factors, presumably pup stimulation, during the postpartum period.     

Instigating and measuring interpersonal aggression and hostility: A methodological contribution

Two experiments were conducted, employing a 2 × 2 factorial design, to assess both 1)a relatively controlled procedure for instigating aggressive inclinations and 2) a way of measuring interpersonal aggression that is much more subtle than most of the laboratory procedures now being used. In both of these experiments half of the subjects were provoked by exposing them to a self-esteem-threatening evaluation ostensibly from a peer. After this “treatment,” in experiment 1 all of the subjects had an opportunity to deliver electric shocks to the supposed other student, much as in many of the laboratory experiments in this area, and then rate that student. Shock intensity was not significantly correlated with the unfavorableness of these latter ratings, as if the subjects had reacted in different ways to the shocks they had delivered. In experiment 2, after the instigating treatment the subjects were allowed to withhold rewards from the other person whenever he made correct guesses on a supposed “ESP task.” In this procedure the behavioral hostility (withholding rewards) was positively correlated with the unfavorableness of the subsequent questionnaire ratings, apparently because the subjects were not fully aware of having expressed hostility.     

Fluoxetine activity on muricidal aggression induced in rats by p-chlorophenylalanine

Fluoxetine is a selective inhibitor of serotonin uptake into serotonergic presynaptic terminals of rat brain. This compound was shown to develop a clinical antidepressant activity. Rat muricidal aggression, which is believed to involve a decrease of brain serotonergic inhibitory control, is also believed to represent a good experimental tool to study the efficacy of antidepressant drugs, which usually inhibit this behavior. In this framework, fluoxetine is also capable of significantly reducing muricidal aggression induced by p-chlorophenylalanine in male Wistar rats.     

Frustration and successful vs. Unsuccessful aggression: A test of Berkowitz' completion hypothesis

Author experiment using a modified version of the Buss' aggression paradigm tested Berkowitz' completion hypothesis, which states unsuccessful aggressive attempts at the frustrator serve as further frustration and intensify aggression. Testing was done by varying the number of successful aggressive attempts for different experimental groups. The experiment indicated first a positive relationship between subjective levels of frustration and aggression, which supports a general frustration-aggression hypothesis, and second that unsuccessful aggressive attempts lead to increased aggression in terms of shock intensity. This was interpreted as supportive of Berkowitz' completion hypothesis, although alternative interpretations in terms of cognitive and behavioral strategies cannot be excluded.     

Repeated exposure to violent and nonviolent pornography: Likelihood of raping ratings and laboratory aggression against women

This study examined the relatively long-term effects of repeated exposure to violent and nonviolent pornography on male' laboratory aggression against women. Self-reported likelihood of raping was also assessed as an individual differences variable that might mediate susceptibility to the effects of pornography and to ascertain whether it predicted actual aggressive behavior. Subjects were randomly assigned to the sexually violent, sexually nonviolent, or control exposure conditions. Those assigned to the sexually violent or sexually nonviolent conditions were exposed over a four-week period to ten stimuli including feature-length films and written and pictorial depictions, whereas control subjects were not exposed to any stimuli. About a week following the end of the exposure phase, subjects participated in what they believed to be a totally unrelated experiment in which aggression was assessed within a Buss paradigm. Exposure to the violent or nonviolent pornographic stimuli was not found to affect laboratory aggression. These data are discussed in terms of a recent analysis of media effects emphasizing the temporary activation of ideas in audience' minds. Likelihood of raping ratings was found to predict laboratory aggression.