The effects of gormone manipulations on aggressive target-biting in mice

Aggressive biting of an inanimate target by mice was studied. Males attacked the bite-target more frequently than females, but this difference disappeared after castration when the response rate of the males approached that of the females. Ovariectomizing the females had little effect on their bite-attack frequencies. Subsequent androgen injections restored the biting-attack frequency of the castrated males to preoperative levels but had little effect on the intact males. Estrogen had little effect on the response frequency of the females, whereas androgen produced a slight increase in their bite-attack frequency. Results indicate that androgen is critical for the maintenance of this aggressive response and that the single subject paradigm utilized in this study was a sensitive measure of aggressive tendencies in mice.     

Dominance assertion in male chimpanzees (Pan troglodytes)

The social relations of three adult males in a captive chimpanzee group were evaluated for 12 months. The observations encompassed a period of transition in the dominance hierarchy providing an opportunity to assess behavioral patterns involved in the initiation of status changes. This study shows that dominance in the chimpanzee is expressed primarily through ritualized and non-contact behavior rather than by overt aggression. In particular, display behavior is important for indicating dominance rank, in communicating aggressive intent, and as a prelude to status struggles. The functional relationships between status, displays and other socio-sexual behavior patterns are presented.     

Visual aspects of centrally elicited attack behavior in the cat: “Patterned reflexes” associated with selection of and approach to a rat

It has been previously suggested that the electrical brain stimulation which elicits quiet-biting attack in the cat actively affects the way the central nervous system processes visual and tactile information concerned with the reflexes involved in the terminal aspects of attack. In order to examine the effects of brain stimulation on a nonterminal aspect of attack – the stimulated cat's selection of and approach to a rat – cats were implanted with attack-eliciting electrodes in both the lateral hypothalamus and the midbrain ventral tegmental area. These cats were then tested in an 8-ft-long cage, one end of which was divided into three, 2-ft-long parallel compartments, whose openings faced the end of the cage from which the cat commenced its approach. An anesthetized rat was placed at the back of one compartment, a bowl of food at the back of another compartment, and the third compartment contained no object. It was found in the first experiment that the attack elicited by nearly all electrodes was selectively directed at the rat. However, the success of the cat in finding the compartment containing the rat varied dramatically for different electrodes in the same cat. Further, these differences were stable and did not change as the cat gained experience with the task. The results suggested that the stimulation of different brain sites in the same cat differentially affected the visual neural mechanisms involved in guiding a cat to a rat. Previous studies have also suggested that the effects of brain stimulation which elicits quiet-biting attack are largely lateralized to the side of the brain stimulated. In order to determine if the effects of stimulation on the neural mechanisms mediating the visually guided approach of a cat to a rat were also lateralized, attempts were made in a second experiment to disrupt the visual input to one side of the brain by unilaterally transecting the optic tract. It was found that this manipulation interfered with the visually guided selective approach to a rat, if the cat was stimulated through hypothalamic or mid-brain electrodes ipsilateral to the optic tract transection, but not if the hypothalamic or midbrain stimulation was on the contralateral (visually intact) side of the brain. However, any final interpretation of the results was confounded by the finding in all of these cats of a complex syndrome of neglect of all contralateral sensory information.     

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.     

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.     

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.     

Why do aggressive movies make people aggressive? an attempt to explain short-term effects of the depiction of violence on the observer

An explanation-approach within the frame of a universal and integrating theory of aggression is favored for understanding the effects of exposure to violence. Kornadt's Motivation Theory of Aggression is used to generate several hypotheses concerning the effects of aggressive movies on a viewer's expectancy-value-cognitions and these are tested in an experiment. The experiment suggests that aggressive stimulation is able to change aggression-related expectancy-value-cognitions in an aggression-facilitating direction. Based on these results, an attempt is made to explain increases in the aggression of viewers in terms of the Motivation Theory of Aggression. © 1993 Wiley-Liss, Inc.     

Effects of alpha and beta adrenergic antagonists on aggressive behavior in male mice

The effects of a variety of alpha and beta adrenergic antagonists were examined on the social encounters of isolated male mice with anosmic male partners. A range of alpha antagonists, including phentolamine, prazosin, and yohimbine, all suppressed social aggression. A range of beta antagonists, including propranolol, atenolol, metaprolol, and ICI 118, 551, also reduced this type of attack. Ethological assessment of the lowest effective dose of these adrenergic antagonists revealed a marked inhibitor action on offensive, social, and nonsocial behavior, while defensive responses and immobility were enhanced. It is concluded that the noradrenergic system has a significant non-specific role in mediating intermale aggression via both alpha and beta adrenergic receptor subtypes. © 1993 Wiley-Liss, Inc.     

Sexual jealousy in young women and men: Aggressive responsiveness to partner and rival

Two studies compared judgments about aggressive components of jealous reactions to the partner and to the rival, specifically, emotional (anger), cognitive (blame), and behavioral components. The first study randomly assigned 172 young women and men to two questionnaires on jealous reactions to mild (flirting) and serious (cheating) transgressions. One questionnaire assessed standards for appropriate behavior and perceptions of how people usually react. The second questionnaire asked people to report how they had reacted or, if not experienced with a sexual transgression, how they would react. The second study asked 113 people to imagine a situation in which they knew their partner had been sexually unfaithful. There were three major findings that were interpreted in the context of courtship, a time when attention is focused on the qualities of one's potential long-term partner. First, the jealous individual's anger and blame were focused more on the partner than the rival. Second, mean anger and blame scores given the partner were well matched. In contrast, the rival received more anger and blame than deemed appropriate and considerably more anger than blame. These data suggest that, in the context of courtship, a rival is not simply a competitor. Third, men were more inclined to think about aggressive action against the rival but women were more emotionally and behaviorally reactive to the rival. The latter result implies that, in the context of competition for an established romantic partner, a rival is more salient for women than for men. © 1993 Wiley-Liss, Inc.