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PubMed1999

Effects of haloperidol on communicative and aggressive behavior in male mice with different experiences of aggression.

Effects of two doses of haloperidol (0.1 and 0.4 mg/kg, 30 min and 24 h, IP) on communicative and aggressive behavior in C57BL/6J male mice have been studied. Some of the mice were without prior experience of aggression ("recruits"); the others had been victorious in 20 daily aggressive confrontations ("experienced winners"). Communicative behavior was estimated as the behavioral reaction to a standard tester (loser) in the partition test. Haloperidol in either dose significantly reduced communicative behavior in the "recruits." but not in the "experienced winners." Significantly fewer attacks, less total attacking time, and total time of aggressive behavior (aggressive grooming + attacks) were demonstrated by the "experiences winners," than by the "recruits," while the latency of the first attack, the number, the total and average duration of aggressive grooming events were significantly higher. In the "recruits," haloperidol dose dependently increased the latency and decreased the number of attacks, the total attacking time, and the total time of aggressive behavior 30 min and 24 h after injection. However, haloperidol did not affect the average or total time of aggressive grooming. Neither dose significantly affected any measure of aggressive behavior in the "experienced winners." It has been concluded that repeated aggression experience reduces the pharmacological sensitivity of the dopamine receptors.

Aggression↗
PubMed1979

Effects of external incentive and aggressive predisposition on aggression reduction.

Female undergraduates (N = 40) received four counteraggression strategies (0%, 10%, 50%, and 150% retaliation) in response to their aggression in a complex reaction time task. They either were or were not offered a monetary incentive to beat their opponent and were divided into those low and high in their initial predisposition to aggression. Four major findings resulted: 1) escalation of aggression to 150% retaliation supported reciprocity over contingent punishment theory. 2) Ss low in aggression were unaffected by strategies, rather than being most responsive to pacifism, as predicted. 3) Ss high in aggression reduced their aggression most to the intermediate 10% and 50% retaliation strategies. 4) An external (monetary) incentive for beating the opponent did not parallel the aggressiveness personality factor as expected. The external incentive reduced the difference between low and high aggression participants and resulted in a linear relationship between retaliation strategy and aggression reduction. This is the first study showing minimum (10%) retaliation to be more effective than pacifism (0% retaliation), but the effect occurred only among the 25% most aggressive Ss when there was no monetary incentive.

Adult↗
PubMed2001

Aggression in the general Swedish population, measured with a new self-rating inventory: The Aggression Questionnaire--revised Swedish version (AQ-RSV).

The aim of the present study was to develop a Swedish self-rating instrument for clinical aggression research based on the American Aggression Questionnaire (AQ), which measures physical aggression, verbal aggression, anger, and hostility. To test this adapted Aggression Questionnaire--revised Swedish version (AQ-RSV), it was mailed to 781 randomly selected individuals, aged 20-40 year. A total of 497 (64%) evaluable AQ-RSV inventories were obtained and analyzed statistically. Drop-out analysis showed that non-responders were most often male and significantly older than responders. Among the responders, AQ-RSV showed significant sex differences in all aggression subscales except Hostility. Aggression was found to vary with age, geographical region, and size of home community. The AQ and the AQ-RSV were comparable in correlations between the four aggression subscales and in alpha coefficients, which indicated considerable internal consistency. Development of the aggression-measuring instrument for Swedish conditions is important not only to study subtraits of aggression but to enable analyses of their relationships to neurobiological and psychiatric variables.

Adolescent↗
PubMed2005

"So I can't blame the booze?": Dispositional aggressivity negates the moderating effects of expectancies on alcohol-related aggression.

OBJECTIVE: The purpose of this study was to determine the effects of alcohol expectancies on intoxicated aggression in men and women while controlling for dispositional aggressivity. METHOD: Subjects were 328 (163 men and 165 women) healthy social drinkers between 21 and 35 years of age. Alcohol expectancies were measured using items from a variety of validated self-report inventories. Following the consumption of either an alcohol or a placebo beverage, subjects were tested on a modified version of the Taylor Aggression Paradigm, in which mild electric shocks were received from and administered to a fictitious opponent during a competitive task. Aggressive behavior was operationalized as the shock intensities administered to the fictitious opponent under conditions of low and high provocation. RESULTS: On their own, alcohol expectancies played a limited role in impacting aggressive behavior. Specifically, alcohol expectancies were significantly related to aggression for men who received the placebo beverage under low provocation and for men who received alcohol under high provocation. A significant main effect of alcohol expectancies was also detected. However, all of these effects were rendered nonsignificant when controlling for dispositional aggressivity. It is important to note that the main effect for beverage group remained significant after controlling for dispositional aggressivity. CONCLUSIONS: Taken as a whole, this pattern of findings suggests that intoxicated aggression is primarily the result of alcohol's pharmacological properties in conjunction with an aggressive personality.

Adult↗
PubMed2000

Effect of dietary protein content and tryptophan supplementation on dominance aggression, territorial aggression, and hyperactivity in dogs.

OBJECTIVE: To evaluate the effect of high- and low-protein diets with or without tryptophan supplementation on behavior of dogs with dominance aggression, territorial aggression, and hyperactivity. DESIGN: Prospective crossover study. ANIMALS: 11 dogs with dominance aggression, 11 dogs with territorial aggression, and 11 dogs with hyperactivity. PROCEDURE: In each group, 4 diets were fed for 1 weeks each in random order with a transition period of not < 3 days between each diet. Two diets had low protein content (approximately 18%), and 2 diets had high protein content (approximately 30%). Two of the diets (1 low-protein and 1 high-protein) were supplemented with tryptophan. Owners scored their dog's behavior daily by use of customized behavioral score sheets. Mean weekly values of 5 behavioral measures and serum concentrations of serotonin and tryptophan were determined at the end of each dietary period. RESULTS: For dominance aggression, behavioral scores were highest in dogs fed unsupplemented high-protein rations. For territorial aggression, [corrected] tryptophan-supplemented low-protein diets were associated with significantly lower behavioral scores than low-protein diets without tryptophan supplements. CONCLUSIONS AND CLINICAL RELEVANCE: For dogs with dominance aggression, the addition of tryptophan to high-protein diets or change to a low-protein diet may reduce aggression. For dogs with territorial aggression, tryptophan supplementation of a low-protein diet may be helpful in reducing aggression.

Aggression↗
PubMed2000

Effect of male-to-male aggressiveness and feed-restriction during rearing on sexual behaviour and aggressiveness towards females by male domestic fowl.

This experiment was one part of a larger study investigating problems of aggression towards females by male broiler breeder fowl. To investigate causal mechanisms, we were interested in determining (1) if feed-restriction during rearing affects behaviour towards females at sexual maturity and (2) if aggressiveness towards females is correlated with general levels of aggressiveness. We compared broiler breeder males with commercial laying strain males, which were either fed ad libitum or were feed-restricted during the rearing phase, and with game strain males, bred for fighting. Differences in behaviour were determined by observing males during interactions with small groups of females.Laying strain males did not behave aggressively towards females, whether feed-restricted or fed ad libitum during rearing. Despite genetic selection for fighting ability, game strain males also were not aggressive towards females. Conversely, broiler breeder males displayed significantly higher levels of aggression towards females than did feed-restricted laying strain males (P<0.02). Broiler breeder males were rough with females during mating, whereas laying strain and game strain males were not. Females struggled more frequently during mating attempts by broiler breeder males (P<0.002) and interfered frequently when these males attempted to mate with other females.From our results, we conclude that (1) feed-restriction during rearing has little effect on the sexual and aggressive behaviour of laying strain males at maturity and (2) selection for aggressiveness has not resulted in males which are more aggressive to females. Aggression towards females appears to be a unique problem occurring in broiler breeder male strains and not a function of feed-restriction.

Journal Article↗
PubMed2004

Do aggressive and non-aggressive antisocial behaviors in adolescents result from the same genetic and environmental effects?

Antisocial behavior (ASB) in adolescents can broadly be separated into two forms; aggressive and non-aggressive. Both are heritable and it has been suggested that aggressive ASB is more heritable. The extent to which genes contribute to the correlation between the two is unknown. Structural equation modeling was applied to a population-based twin sample of 258 twins pairs aged 11-18 to estimate the heritability of each form of ASB and to estimate the extent to which the phenotypic correlation was the consequence of shared genes and environmental factors. Non-shared environment and genetic factors substantially influenced both forms of ASB. The heritability of aggressive (but not non-aggressive) ASB was significantly higher in girls than in boys. Combining both sexes, a model in which the genetic effects on aggressive and non-aggressive ASB were identical could be rejected. Our results suggest a partial genetic overlap with a specific genetic effect contributing to the variance of aggressive ASB and a stronger genetic effect on aggression in females than in males.

Adolescent↗
PubMed1977

Muscarine- and carbachol-induced aggressions: fear and irritable kinds of aggressions.

In unaneasthetized and unrestrained cats, muscarine and carbachol were injected into the cerebral ventricles. The kind of aggressive behaviour depended on the cholinomimetic drug and was classified as fear and an irritable kind of aggression. Muscarine induced the fear kind of aggression. The aggressive behaviour was usually preceded by attempts to escape and the attack was relevant to the situation. For the attack the presence of some threatening agent was needed. The aggression was accompanied by intense motor but less autonomic activation. On the other hand, carbachol induced an irritable kind of aggression and had the following characteristics: for the attack the presence of some threatening agent was not needed; the attack was not relevant to the situation; the aggression was not preceded by attempts to escape; and the aggressive behaviour was accompanied by intense motor and autonomic activation. It is concluded that cholinoceptive mechanisms are involved in the control of aggressive behaviour.

Aggression↗
PubMed1992

Aggression in boys with attention deficit-hyperactivity disorder: methylphenidate effects on naturalistically observed aggression, response to provocation, and social information processing.

High and low-aggressive boys with attention deficit-hyperactivity disorder (ADHD) were compared and the effects of methylphenidate were examined on measures from three domains of aggression: (1) directly observed verbal and nonverbal aggressive behaviors exhibited in the context of a day treatment program, (2) aggressive responding when provoked during a laboratory task, and (3) social information processing patterns exhibited on tasks designed to tap the putative cognitive components of aggression. The high-aggressive (HA) and low-aggressive (LA) subgroups differed significantly on observational measures of aggression and on the laboratory provocation task, but the HA group showed more deviant cognitions on only one of the numerous measures of social information processing. Regarding medication effects on the direct observation measures, methylphenidate decreased aggression for both subgroups. On the laboratory provocation task, methylphenidate had only minimal effects. Significant drug effects were obtained on only two recall social information processing measures.

Aggression↗
PubMed2006

A longitudinal study of relational aggression, physical aggression, and children's social-psychological adjustment.

Although great strides have recently been made in our understanding of relational aggression and its consequences, one significant limitation has been the lack of prospective studies. The present research addressed this issue by identifying and assessing groups of relationally aggressive, physically aggressive, relationally plus physically aggressive (co-morbid), and nonaggressive children during their third grade year in elementary school and then reassessing them a year later, during fourth-grade (N = 224, 113 girls). Two aspects of social-psychological adjustment were assessed during both assessment periods including internalizing difficulties (i.e., withdrawal, depression/anxiety, and somatic complaints) and externalizing problems (i.e., aggressive behavior, delinquency). It was revealed that the strongest predictor of future social-psychological adjustment problems and increases in these problems from third to fourth was the combination of relational and physical aggression. Relational aggression also contributed unique information, relative to physical aggression, in the prediction of future maladjustment. Implications of these findings for future research and prevention efforts, particularly for aggressive girls, are discussed.

Aggression↗
PubMed2005

The effects of the D1 receptor antagonist SCH-23390 on individual and aggressive behavior in male mice with different experience of aggression.

The dopaminergic systems of the brain are known to be involved in the mechanisms of aggression. The present report describes studies of the effects of acute administration of the dopamine D1 receptor antagonist SCH-23390 (0.1 mg/kg, i.p., over 30 min) on the individual and aggressive behavior of male mice of the line C57BL/6J with different experience of aggression. A group of animals with no previous experience of aggression responded to administration of this agent with decreases in direct aggression (attacks), though the total time of hostile behavior, i.e., the sum of the durations of attacks, aggressive grooming, and scattering of foreign litter, showed no change. The agent had no effect on the aggressivity of animals with 20 days of experience of agonistic confrontations. The discussion addresses the possible development of pharmacological densensitization of dopamine D1 receptors in aggressive males in response to prolonged activation of the dopaminergic systems in conditions of repeated experience of aggression, as demonstrated previously.

Aggression↗
PubMed1987

Mammary stimulation and maternal aggression in rodents: thelectomy fails to reduce pre- or postpartum aggression in rats.

In mice, tactile stimulation of the nipples appears to be critical for the onset of postpartum maternal aggression. Surgical removal of the nipples (thelectomy) blocks aggression if performed prior to parturition. In rats, indirect evidence suggests a similar role for nipple stimulation in maternal aggression. Two experiments were undertaken to determine whether thelectomy prior to mating reduces pregnancy-induced and/or postpartum aggression in this species. In the first, thelectomized and sham-thelectomized females were subjected to home cage tests (pups, if any, present) with unfamiliar male intruders on Gestation Days 18 and 21 and Lactation Days 3 and 5. Additional groups of thelectomized females were tested one time only on either Lactation Day 5 or 12. Thelectomized and control females were equally aggressive; postpartum, nearly all females in both groups attacked. Experiment 2 used females that were hysterectomized-ovariectomized (HO) on Gestation Day 16. Such females are not aggressive prior to initiating maternal behavior, but become highly aggressive (over 80% attacking) after commencing maternal care. Females again were thelectomized or sham-thelectomized prior to mating. On Day 16 HO was performed, and 48 hr later continuous exposure to pups was begun. After the females had displayed maternal behavior for 1.5-2 days, intruder tests were conducted. All females attacked at least once, with no differences between treatment groups. Thus thelectomy does not reduce maternal aggression in the rat. This finding, however, does not preclude a role for tactile ventral stimulation in mediating maternal aggression.

Aggression↗
PubMed1984

The effect of television-mediated aggression and real-life aggression on the behavior of Lebanese children.

This study investigated the effect of television-mediated aggression and real-life aggression on the behavior of Lebanese children. The sample consisted of 48 boys and 48 girls of Lebanese origin who were students in an elementary school in Beirut, Lebanon. After controlling for pre-experimental aggression, the subjects were randomly assigned to one of the following treatment conditions: human-film aggression, cartoon-film aggression, neutral film, or real-life (act of war) aggression. The results indicated that boys as a group were more aggressive than girls and exhibited more imitative aggression after viewing both violent film and real-life violence. Girls were not more violent after viewing filmed aggression but were affected by the real-life violence. Comparisons of Bandura's work within the Lebanese culture are made.

Aggression↗
PubMed1990

Hormone-dependent aggression in female rats: testosterone implants attenuate the decline in aggression following ovariectomy.

Female rats were individually housed with a sterile male for a 4- to 5-week period. Each female was then tested for aggression toward an unfamiliar female intruder at weekly intervals. Those females that displayed a high level of aggression on each of three weekly tests were ovariectomized and given subcutaneous implants of testosterone-filled tubes, ovariectomized and given subcutaneous implants of empty tubes, or sham-ovariectomized and implanted with empty tubes. These implants should produce a serum testosterone concentration of about 0.6 ng/ml, compared to 0.17 ng/ml in intact females. Beginning 1 week postoperatively, the aggression of each female was tested weekly for 4 weeks. Ovariectomized females with testosterone implants displayed a level of aggression significantly higher than that of ovariectomized females with empty implants on 3 of 4 weekly tests. The level of aggression by females with testosterone implants was not significantly different from that of sham-ovariectomized females on the first postoperative test. Additional observations showed that testosterone implants did not produce an increase in aggression in females whose preoperative level of aggression was low. Further, Silastic implants containing estrogen (1 to 2 mm long) sufficient to maintain a serum estrogen level of 20 to 30 pg/ml also attenuated the decline of aggression following ovariectomy. These results suggest that testosterone and estrogen may both contribute to the biological substrate of hormone-dependent aggression in female rats.

Aggression↗
PubMed2006

Concerns, dispositions and behaviors of aggressive drivers: what do self-identified aggressive drivers believe about traffic safety?

INTRODUCTION: The purpose of this investigation was to identify beliefs, driving personality dispositions, and behaviors that distinguish self-defined aggressive drivers from non-aggressive drivers. METHOD: Telephone surveys were used to identify self-reported aggressive drivers (n=305) who were compared to non-aggressive drivers (n=1,715) concerning their beliefs, driving behaviors, and self-described driving dispositions. RESULTS: Aggressive drivers, compared to non-aggressive drivers, were less concerned about speeding, aggressive driving, and cell phone use while driving, yet were more likely to have had an encounter with another aggressive driver. They were also more likely to report that they had driven when they knew they had too much to drink, yet they felt less likely that they would be stopped by the police. CONCLUSION: Aggressive drivers display many dispositions that define them as high risk drivers and public information/motivational campaigns alone will likely be ineffective with this group of drivers. Strategies that combine visible enforcement with widespread publicity campaigns appear to be necessary.

Accidents, Traffic↗
PubMed1995

Moderating role of trait aggressiveness in the effects of violent media on aggression.

Three studies were conducted to test the hypothesis that high trait aggressive individuals are more affected by violent media than are low trait aggressive individuals. In Study 1, participants read film descriptions and then chose a film to watch. High trait aggressive individuals were more likely to choose a violent film to watch than were low trait aggressive individuals. In Study 2, participants reported their mood before and after the showing of a violet or nonviolent videotape. High trait aggressive individuals felt more angry after viewing the violent videotape than did low trait aggressive individuals. In Study 3, participants first viewed either a violent or a nonviolent videotape and then competed with an "opponent" on a reaction time task in which the loser received a blast of unpleasant noise. Videotape violence was more likely to increase aggression in high trait aggressive individuals than in low trait aggressive individuals.

Aggression↗
PubMed1999

The distinction between beliefs legitimizing aggression and deviant processing of social cues: testing measurement validity and the hypothesis that biased processing mediates the effects of beliefs on aggression. Conduct Problems Prevention Research Group.

In 2 studies the authors examined knowledge and social information-processing mechanisms as 2 distinct sources of influence on child aggression. Data were collected from 387 boys and girls of diverse ethnicity in 3 successive years. In Study 1, confirmatory factor analyses demonstrated the discriminant validity of the knowledge construct of aggression beliefs and the processing constructs of hostile intent attributions, accessing of aggressive responses, and positive evaluation of aggressive outcomes. In Study 2, structural equation modeling analyses were used to test the mediation hypothesis that aggression beliefs would influence child aggression through the effects of deviant processing. A stronger belief that aggressive retaliation is acceptable predicted more deviant processing 1 year later and more aggression 2 years later. However, this latter effect was substantially accounted for by the intervening effects of deviant processing on aggression.

Aggression↗
PubMed2000

Aggression and sociometric status among peers: do gender and type of aggression matter?

The connections between the use of different types of aggression (direct physical, direct verbal, and indirect) and sociometric status among same-sex and opposite-sex peers were studied. The subjects were 209 ninth-grade adolescents. Although an adolescent's aggression in general was related to being rejected by peers, a different picture emerged when the shared variance between types of aggression was controlled: The partial correlations showed that when the level of direct (physical and verbal) aggression was kept constant, increases in indirect aggression did not explain variance in peer rejection scores. On the contrary, the use of indirect aggression contributed (especially among boys) to social acceptance by peers. The direct (physical and verbal) forms of aggression were unrelated to adolescents' social acceptance scores. No clear differences were detected between girls' and boys' acceptance or rejection of their aggressive peers, despite the finding that boys seemed to tolerate indirect aggression better than girls did.

Adolescent↗