Effects of reactivity to dorsal stimulation and social role on aggressive behavior in laboratory rats

Rats were selected on the basis of reactivity to dorsal tactile stimulation and then tested in a resident-intruder paradigm. While reactivity of residents did not influence the occurrence of agonistic behaviors or wounding of residents and intruders, reactivity of intruders did affect offensive and defensive patterns of interactions and the wounds sustained by residents and intruders. Subsequent to resident-intruder testing, rats were tested for shock-induced aggression. The pattern of the results and the results of additional experiments demonstrated that resident-intruder experience could affect subsequent shock-induced aggressive behavior.     

Comparison of agonistic behavior in individually-housed male mice with those cohabiting with females

Videotape recordings of male mice group-housed, individually-housed and cohabiting with females, were rated for their agonistic behavior in a “standard opponent” test. Previously mated male mice showed more fighting than isolated or grouped males. Marked differences in other social and non-social behaviors, which could not be accounted for in terms of increased fighting, were not evident. These results suggest that agonistic behavior may be usefully studied by examining male mice that have cohabited with females. One obvious advantage is that such mice cannot be dismissed as being “socially deprived,” as is sometimes claimed for individually-housed mice. Other advantages are that aggressiveness is induced quickly, at high levels, and the mice appear very sensitive to hormone manipulation following castration.     

Interspecific aggression and reactivity in rats: Effects of selective raphe lesions and additional olfactory bulb ablation

Large depletion of brain 5 HT has been shown to induce mouse-killing behavior in the rat. Selective lesions of the raphe nuclei have been investigated in order to determine whether the various components of the 5 HT system exert some specific control over this aggressive behavior. Electrolytic lesions of the dorsal or the median raphe nucleus do not induce mouse killing, whereas combined lesions of these nuclei elicit this behavior in about 40% of naive rats. Consequently, it appears that serotonergic neurons originating in the dorsal and median raphe nuclei work synergistically in mediating inhibitory control over mouse-killing behavior. Loco-motor activity is increased in novel environments by each of the selective lesions and to a larger extent by combined raphe lesions; 24 hours activity in resting conditions is unchanged during the light period, and increased during the dark period of the daily cycle by the various lesions. As it has been shown previously that hyper-activity in response to novelty following raphe lesions is not directly related to the 5 HT decrease in the brain, it appears that interspecific aggression and motor responsiveness must not be dependent on the same neural substrate within the raphe nuclei. The raphe lesions do not facilitate the elicitation of mouse killing by further olfactory bulb ablations, in contrast to earlier results where bulbectomy facilitated the induction of this behavior by raphe lesions.     

Social and personal determinants of workplace aggression: Evidence for the impact of perceived injustice and the Type A Behavior Pattern

Four hundred fifty‐two employed persons rated the frequency with which they had been the victims of a wide range of aggressive actions at work. In addition, they also rated the frequency with which they themselves had aggressed against others in their workplaces. Three hypotheses were investigated: (1) covert forms of aggression, in which aggressors seek to conceal their identity from target persons, are significantly more frequent in workplaces than overt forms of aggression; (2) the greater the perceived injustice reported by employees, the greater their tendency to engage in workplace aggression; and (3) the higher individuals' scores on a measure of the Type A Behavior Pattern, the greater their reported frequency of engaging in various forms of workplace aggression. Results offered support for all three hypotheses. In addition, several demographic variables (participants' age and gender; the physical location of their workplaces) were also found to play a role in the occurrence of workplace aggression. Together, these findings were interpreted as underscoring the importance of establishing close conceptual links between research on workplace aggression and basic research on human aggression. Aggr. Behav. 25:281–296, 1999. © 1999 Wiley‐Liss, Inc.     

Fighting,nonagonistic social behavior,and exploration in isolation‐reared rats

Sixty hooded Long‐Evans rats were assigned to one of three conditions: isolation‐rearing (from 14–30 days of age), brief isolation (from 28–30 days of age), and normal (no isolation). From day 14 to day 21, the isolation‐reared animals were maintained in an incubator set at 35°C to prevent hypothermia and were separated from each other by Plexiglas. They learned to nourish themselves by lapping milk that continuously flowed down one side of the enclosure. Thereafter, they were housed in standard hanging wire cages. Unlike previous studies of isolation at this age, there were no significant weight differences between the isolation‐reared group and the two control groups. At 30 days of age, the three groups were compared on fighting (serious and play), nonagonistic social behaviors (following and crawling under), and exploratory behavior (open‐field ambulation). The isolation‐reared group was significantly different from the normal group on all measures (isolates were higher on all measures except exploration). The isolation‐reared animals showed significantly more serious fighting (aggression) than the brief isolation animals, whereas these two groups did not differ on other behaviors. This methodology allows for the study of isolation‐rearing without the nutritional confounds found in previous research and shows an effect on aggression that is not accounted for by recent isolation. Aggr. Behav. 25:211–223, 1999. © 1999 Wiley‐Liss, Inc.     

Gonadal hormones and intrasexual aggressive behavior in female bank voles (Clethrionomys glareolus)

The effects of gonadal hormones on aggressive behavior in the female bank vole was investigated in 10 min home cage tests. Ovariectomized (ovx) or intact females injected with oil, with progesterone (P), with a mixture of progesterone and estrogen (P+E), or with testosterone (T) alone were confronted in a resident-intruder test with unfamiliar, nonoperated females as intruders. Intact females showed aggressive behavior more frequently than ovx females. Ovx females injected with P, with P+E, or with T made significantly more attacks, and these attacks lasted longer than those observed for oil-treated voles. The results indicate that P, the typical female hormone, is responsible for aggressive behavior in female bank voles; however, only T increased the duration of interfemale aggression. Aggr. Behav. 24:63–70, 1998. © 1998 Wiley-Liss, Inc.     

Early antecedents of spouse abuse

Males taken into police custody for reported spouse abuse (n = 19) and a matched control group (n = 19) were asked to describe the drinking habits of their parents and the extent of intra-family violence witnessed by them as children. The retrospective data were compared to the participant's own present alcohol use and aggressiveness (CTS). Excessive paternal drinking and intra-family violence were recalled significantly more often by the spouse abusers than by the controls. A latent structure model suggested that the accumulated violence history was less well predicted by either paternal violence or present aggressiveness than by the direct and indirect effects related to drinking. Context-specific social learning could explain why the parental drunken violence behavior pattern witnessed by the child was repeated by the adult spouse abuser. Aggr. Behav. 23:239–243, 1997. © 1997 Wiley-Liss, Inc.     

Aggression and testosterone: Testing a bio-social model

Based upon reports of a positive correlation between circulating testosterone levels and aggression, we draw upon evolutionary psychology to place the action of testosterone in a broader perspective. We propose that testosterone affects competitive status-seeking and that under certain circumstances (including youth) this is expressed as aggression. Involvement in aggression in turn is associated with adherence to an instrumental social representation of aggression which justifies aggression as a means of imposing control over others and increasing self-esteem. Measures of salivary testosterone, masculinity, preferred social representation of aggression, and multiple aggression scales were collected from an undergraduate sample of 119 men. An Aggression factor was derived from principle components analysis of the aggression measures. The strongest correlates of Aggression were holding an instrumental social representation of aggression and youth. Testosterone showed no significant relationship to the single or aggregate measures of aggression or to any of the other psychometric measures. We suggest ways in which previous work may have over-estimated the strength of the association between circulating testosterone and aggression and discuss the possible relationships between age, social representation, and aggression. Aggr. Behav. 23:239–238, 1997. © 1997 Wiley-Liss, Inc.     

Expectations and prescriptions for responding to peer aggression: The adolescent offenders' perspective

The purpose of the current research was to investigate adolescent offenders' perspectives about responses to interpersonal aggressive encounters. Specifically, participants' perspectives were assessed regarding the role of a bystander when either a friend or an acquaintance of the bystander was the victim of an aggressive act. Two aggressive acts were presented. First, the bystander witnessed an acquaintance stealing from the victim. Second, the bystander witnessed an acquaintance hitting the victim. Participants were asked to indicate (a) if the bystander would do anything (bystander expected behavior), (b) what the bystander would do (expected behavioral action), (c) if the action would be the right thing to do (evaluation of bystander expected behavioral action), and (d) what the bystander should do in response to the violation (prescribed bystander behavioral action). Results indicate that the adolescent offenders' perspectives varied as a function of offender status, type of aggressive act, as well as relationship of the victim to the bystander. Aggr. Behav. 23:149–160, 1997. © 1997 Wiley-Liss, Inc.