Sex differences in aggressive behaviour in various strains of mice

Two nonalbino inbred (C57 BL/6 and C3H/He) and one albino strain (Swiss) of mice were compared for female aggression toward intruders: 1 in period of lactation, 2 in nonlactating state and (3) in nonlactating state but previously rubbed with urine of lactating females; and for male aggression toward familiar or unfamiliar opponents. The results showed that resident females of the C57 and Swiss strain vigorously attack lactating intruders introduced into their cages. This effect was mediated by urinary cues emitted by the latter mice. It was also shown that Swiss residents displayed aggression towards nonlactating females, irrespective of their strain. Groups of C57 residents reacted most aggressively towards Swiss females, less aggressively towards C3H intruders, but did not show any aggression towards their own nonlactating conspecifics. In contrast, none of the C3H resident female groups displayed aggression towards intruding females of any category or strain. The results also showed that the males of the three strains displayed little (Swiss and C3H) or no aggression (C57) towards familiar opponents, whereas they directed increased aggressive responses towards unfamiliar ones. Comparisons among the three strains of mice revealed that Swiss males were the most aggressive in either situation. On the other hand, the finding that C3H males showed aggressive responses suggested that male and female aggression are, in this strain, under separate genetic or hormonal control.     

Intervention for aggressive victims of school bullying in Hong Kong: a longitudinal mixed-methods study

The distinction between aggressive and passive victims of school bullying is well documented. Aggressive victims exhibit restlessness and hot-temperedness, are easily provoked, and take revenge when irritated, whereas passive victims are quiet and timid when attacked or insulted and withdraw rather than retaliate. To date, there has been no evidence-based evaluative study examining interventions designed specifically to reduce aggressive victimization, and neither has there been an inclusive assessment screening of high-risk aggressive victims prior to intervention. This study addressed these research gaps by employing multi-stage assessment procedures and a mixed-mode methodology in a one-year longitudinal design. Data were collected from student self-reports, parent and teacher rating scales, and individual structured interviews with students, parents and teachers. A total of 269 potential high-risk aggressive victims were identified from among 5,089 schoolchildren, 68 of whom were screened out and randomly assigned to 10 treatment groups, with 39 completing a one-year follow-up study. Multivariate analysis of variance identified significant improvements in physical and verbal victimization (F(2,47, 93.99) = 10.73, p < 0.01), verbal victimization (F(2.74, 104.14) = 12.80, p < 0.01) and social exclusion scores at the three follow-up assessments compared to the pre-treatment scores, and the qualitative results were consistent, showing participants' cognition, emotion, and behavior to have been positively reconstructed by the group intervention. The consistent quantitative and qualitative results confirm that the cognitive-behavioral group therapy program reported herein is effective in reducing aggressive victims' anxious and depressed emotions and reactive cognition.     

A comparison of 8- and 11-year-old girls' and boys' participation in specific types of rough-and-tumble play and aggressive fighting: Implications for functional hypotheses

Study 1 compared the extent to which 8- and 11-year-old girls and boys (N = 86) participated in specific types of rough-and-tumble play. It used an observational methodology. The data were used to test two prominent hypotheses about the evolutionary function of this general category of play behaviour that have been applied to children, especially boys, of this age. One is that rough-and-tumble play provides practice for the development of real fighting skills and the other that it serves as a safe way to establish/display social dominance. Both hypotheses predict that boys will engage in more rough-and-tumble play than girls, especially those types that are used in fighting/dominance contests. Boys were found to engage in significantly more chase initiation activities, more bouts of brief rough-and-tumble play, more bouts of restraining and more bouts of boxing/hitting than girls. These data provide some support for the two hypotheses, although significant sex differences were not found for all types of rough-and-tumble play observed. No significant age differences were obtained, suggesting that the two hypotheses may be applicable throughout the 8- to 11-year-old period and not just at the end of it as previous research had suggested. Study 2 presented observational data concerning the motor patterns used in aggressive fighting. In all but one case, there were no significant differences in the extent to which 8/9- and 10/11-year-old girls and boys employed wrestling, hitting and restraining, supporting the view that the practice fighting hypothesis is relevant throughout the 8-11-year-old period. It was argued that age and sex differences provide a useful means of scrutinising functional hypotheses, and that splitting behavioural categories that contain disparate action patterns facilitates more refined tests of those hypotheses. © 1996 Wiley-Liss, Inc.     

Social isolation,aggression, and dominance in attacks in juvenile angelfish,Pterophyllum scalare

The effects of social isolation on aggressive behavior and rank order have been investigated in small groups of juvenile angelfish, Pterophyllum scalare. An experimental protocol including a “double transfer” of the subjects was used, in which fish were transferred to new aquaria in groups, before subsequent isolation and regrouping. A significant decrease in aggression was observed in the first recording session following both isolation and group transfer, after which the level returned to that recorded in the home tanks. The social hierarchy was also perturbed, but changes generally involed the two highest ranking fish in two out of the three groups, and were found not to be statistically significant. The behavior patterns are interpreted as adaptive responses to environmental change. © 1993 Wiley-Liss, Inc.     

Is monkey maternal abuse of offspring aggressive behavior?

This study was intended to probe the aggressive nature of monkey infant abuse by comparing the morphology of abusive behavior patterns with that of patterns allocated to both aggression and other categories of behavioral repertoires of macaques. This morphological analysis indicated that most abusive patterns should not be classified in the aggression category as they, at the motor end, differ greatly from macaque aggressive acts. In contrast, they perfectly resemble behaviors that monkeys usually display while manipulating inanimate objects. The implications of this finding for the pathogenic study of monkey infant abuse are discussed.     

The assessment of individual “Aggressiveness” in pigeons by a variety of means

Pigeons attack or threaten animate and inanimate targets. The assessment of their aggressiveness was studied by exposing them in their home cages to three different stimuli: the experimenter's hand, a live pigeon, and a rear-projected conspecific image when the birds were exposed to intermittent access to food. A positive correlation between the hand test and live pigeon test was evident, but no relationship between either of these responses and the response to a pictorial image was observed. These results combined with other ethological observations cast doubts on the usefulness of schedule-induced responses to pictorial targets in the assessment of the individual aggressiveness in pigeons, but suggest that the hand test is an adequate and reliable procedure for such evaluations.     

Opposite strain-dependent differences for intermale aggressive behavior elicited by individual housing and housing with a female in the mouse

Male mice of the C57BL/6 strain show a significant increase in aggression toward a nonaggressive male conspecific following 72 hr of individual housing. However, this increase was no longer evident following 2 weeks of individual housing. When housed with a female, C57BL/6 mice show significantly more aggression than singly housed mice of the same strain after 72 hr as well as 2, 4, 8 weeks of differential housing. Male C57BL/6 mice housed with a female also show significantly higher levels of aggression than DBA/2 mice living in the same housing condition after 4 or 8 weeks of differential housing. Finally, male DBA/2 mice individually housed for 8 weeks are significantly more aggressive than mice of the same strain housed with a female for the same time. These results indicate that the increase in aggressive behavior observed following isolation and cohabitation with a female in the mouse is not the same phenomenon. © 1994 Wiley-Liss, Inc.     

A Meta-Analysis of the Distinction between Reactive and Proactive Aggression in Children and Adolescents

The present meta-analytic review aimed to clarify divergent findings concerning the relation between reactive and proactive aggression in children and adolescents. Fifty-one studies with 17,965 participants were included in the analysis. A significant correlation between reactive and proactive aggression was found. The strength of this relation varied considerably between studies, from -.10 to .89. Observational assessment and tilt/noise tasks were associated with smaller correlations than questionnaires. Within the large group of questionnaire studies, studies disentangling the form and function of aggression found lower correlations than studies that did not disentangle form and function. Among questionnaire studies, higher reliability was associated with larger correlations. Effect size did not depend on other study characteristics such as sample type, age, and informant type. It is concluded that reactive and proactive aggression are most clearly distinguished with behavioral observations and questionnaires that unravel form and functions of aggression.