An empirically derived scoring system for intermale aggression in mice

Scoring systems used to assess intermale aggression have been characterized by arbitrary scales and wide variability in the behaviors selected for measurement. The use of such different systems severely limits the ability of investigators to make meaningful comparisons among studies and indicates that there is a need for a common, statistically derived evaluative system for intermale aggression. We measured the frequency and duration of five major components of agonistic behavior exhibited by intact males toward olfactory bulbectomized stimulus males and then analyzed the data using a number of univariate and multivariate procedures. The results were used to generate two statistically based scoring systems, one a short-form index and the other a composite index for more detailed studies of aggression. It is hoped that these statistically derived systems will be adopted by other investigators to increase methodological congruence in the field.     

Effects of midbrain central gray lesions on spontaneous and electrically induced aggression in the rat

Large electrolytic lesions were placed in the midbrain central gray of male rats. Their effects on hypothalamically induced aggression, switch-off behaviour, and locomotion were investigated. A number of these animals were also tested for territorial intermale aggression in order to compare electrically induced and spontaneous aggression. Large lesions resulted in an increase of the current threshold to induce aggression by hypo-thalamic stimulation. Smaller, but still quite large, lesions decreased the threshold current for hypothalamic aggression. After the operation a decrease in the threshold for switch-off was present, both in the experimental and the control group. Current thresholds for locomotion were decreased after the lesions only in the experimental group. Spontaneous aggression was temporarily decreased after the lesion. No indication was found that other behavioural elements of the animal were distorted by the lesion. The parallel between the effects on spontaneous and electrically induced aggression makes it attractive to ascribe a role to the neural circuit of hypothalamus and central gray in territorial aggression. However, even with large lesions the animals were still capable of fighting, hence the central gray is not indispensable. An attempt was made to explain the differential effects that differently sized central gray lesions have on hypothalamic aggression.     

Naturalistic versus experimental approaches to aggression; theoretical and methodological issues

Various strategies to study human aggression are described, accompanied by a discussion of four major issues. It is concluded that the three major goals of research, precise measurement, realism, and generality, cannot be achieved in a single study or series of studies using only one paradigm. Investigators of a particular problem need to develop a research program that incorporates a number of strategies; hypotheses generated “in the street” need to be tested in the laboratory and vice versa.     

Visual target control of schedule-induced aggression in white king pigeons (columba livia)

Visual target control of schedule-induced attack was studied in domesticated pigeons by exposing them to successive and simultaneous target preference procedures involving a fixed-time food schedule and projected target images. Pigeons preferred attacking an image of a conspecific head over a headless bird regardless of the height of the latter. Images of an intact bird and of a head alone were equally effective in controlling attack and more effective than the headless bird. Neither the eye nor four. other head-related features exclusively controlled attack. The combined results suggest that the head of an intact conspecific target selectively controls schedule-induced attack and that the effectiveness of the head in directing attack is inversely related to its physical integrity as a unit without regard to specific features. These results are consistent with reports that the head and head-related features of an intruder control reproductive aggression in birds.     

The reinforcing value of several types of aggressive behavior: A review

Field observations of “surplus killing” and laboratory studies of operant performance rewarded by prey-killing opportunities suggest that predatory behavior is positively reinforcing. Similarly, both repeated encounter and operant performance studies suggest that intraspecific aggression can be positively reinforcing for successful aggressors. While a few studies suggest that defensive aggression under aversive conditions may also be positively reinforcing, it appears that when appropriate response modes are available escape and/or avoidance are preferred to attack. Studies of the reinforcing properties of aggression-eliciting brain stimulation are in general agreement with these conclusions, but methodological problems with these latter observations render them less compelling. The progressive escalation of aggression seen in “warm-up effects” of birds and fish, “priming effects” of mice, and ecstatic violence of humans may be analogous processes based on the positively self-reinforcing characteristics of some kinds of aggression. The transient reductions of aggression which appear as refractory periods and satiation effects in a variety of species may reflect temporary reductions in the reinforcing value of aggression. All these temporal effects must be considered in the evaluation of experiments on the reinforcing value of aggression. More generally, it is possible that these temporal fluctuations reflect the operation of common motivational processes (aggressive states) which regulate overt aggression by changing its reinforcing value.     

The effects of negative reinforcement for irritable aggression on resident-intruder behavior

This experiment demonstrated that rats trained to display elevated levels of shock-induced aggression in a negative reinforcement paradigm displayed more boxing behavior than yoked control groups in a later test in which intruder rats were placed in the home cage of resident rats. Resident or intruder status did not affect the influence of the negative reinforcement procedure on the observed resident-intruder behavior of trained animals; however, naive intruders paired with trained residents displayed increased defensive behavior, suggesting that negative reinforcement for shock-induced aggression affected the behavior of these residents.     

Effects of medial preoptic hypothalamus anterior lesions on three kinds of behavior in the rat: Intermale aggressive,male-sexual,and mouse-killing behavior

Large lesions in the medial preoptic area-anterior hypothalamus (MPOA-AH) of adult male S3 rats reduce both intermale aggressive behavior and male sexual behavior considerably, but mouse-killing behavior is not impaired. Daily treatment with high doses of testosterone propionate for 21 days does not restore these behavioral effects. Smaller lesions in the same area affect male sexual and intermale aggressive behavior differently; in the frontal part of the MPOA-AH they affect aggressive behavior, while in a more caudal part they affect sexual behavior. Indications were found that lesions in specific parts of the stria terminalis and the medial forebrain bundle inhibit aggressive and sexual behavior.     

Situational antecedents of children's anger experiences and subsequent responses to adult versus peer provokers

The purpose of this study was to examine children's reported experiences of anger and their means of expressing anger in their interactions with high versus equal status individuals. Parents and teachers represented high status while siblings and peers represented equal status. Sixth grade children were asked to cite situations in which they experience anger in interaction with peers versus adults and to indicate their typical responses to these situations. We identified 13 categories of situations in which anger was experienced and 11 categories of response to these situations. Anger was experienced in interaction with both high and equal status provokers but of the situations that were identified as producing experiences of anger, nine were reported as occurring differentially in interaction with adults versus peers of the responses to the experience of anger, seven responses were cited differentially in interaction with peers versus adults. The typical responses to adult provoked anger were generally more passive than those to peer provoked anger. Girls more than boys indicated experiencing anger due to adult's task demands but tended to express less overt anger in their interactions with adults than did boys. These findings are consistent with the view that high status of the provoker servers only to inhibit the expression of anger but does not lessen the anger experience itself.     

Intersexual aggression and male sexual activity in captive rhesus macaques

Rape has been posited to be an outgrowth of male reproductive strategies. Forced copulations may have evolved as a consequence of the low parental investment made by males in producing and raising offspring. We designed a laboratory experiment which paired rhesus macaque males with females in order to assess the influence of intersexual aggression on male sexual activity. Younger and older adult males had comparable levels of sexual behavior, but younger males were more aggressive towards females than were older males. In addition, females threatened younger males more than older males. Male attacks on females did not result in sexual intercourse. On the contrary, a negative correlation existed between male aggression towards females and male success at achieving intromissions. Female aggression towards males appeared to be an effective tactic which reduced the chances of sexual intercourse. We conclude that intersexual aggression acts either as a mechanism of dominance assertion or as a means to increase spatial distance between individuals. These data do not support the idea that rape in humans has an evolutionary foundation derived from male reproductive strategies.