Genetic analysis of “Spontaneous” intermale aggression in mice

“Spontaneous” intermale aggression was investigated in seven inbred strains of mice. A positive interstrain correlation and cross-correlation was found for two indices of fighting intensity, ie, accumulated attacking time and number of attacks. The strain aggressiveness level (percent of mice fighting in each strain) does not correlate with the intensity of aggressive behavior. It has been shown by using a genetical analysis performed on C57BL/6 and BALB/c strains, their reciprocal F₁ hybrids, and back-crosses that these indices of intermale aggression are under different genetic control. Aggressive behavior intensity depends on the additive effects of genes. The control of strain aggressiveness level revealed that a high level of aggressiveness was dominant. No reciprocal effects were found. The level of aggressiveness and the intensity of fighting seem to represent different aspects of aggression and may be controlled by different genetic mechanisms.     

Variables affecting establishment of schedule-induced attack on pictorial targets in White King pigeons.

White King pigeons exposed to food schedules before introduction of a colored photograph of a pigeon showed sustained schedule-induced attack on that image; additional birds given an early introduction to both the photograph and the schedule subsequently attacked the image at lower rates. Other pigeons attacked a second photograph of a pigeon regardless of whether it was introduced early or late. The late-introduction procedure was also effective in establishing attack on a projected image of a conspecific. The combined results showed that 14 of 17 White King pigeons given a late introduction to a pictorial target exhibited sustained attack against it and that a pigeon's initial reaction to a photograph of a conspecific when introduced early was a good predictor of subsequent schedule-induced attack on it.     

Attack-target attributes and pigeon aggression: Accessibility,vocalization, and body movements

Characteristics of the attack-target in laboratory tests appear to greatly influence the tendency for aggression to be initiated, maintained, and stopped. To address this question, accessibility, target movement, and vocalization among pigeon conspecifics were investigated in two different aggression tests: 1) paired aggression (PA); and 2) schedule-induced aggression (SI). In the PA test, dominant and subordinate roles formed quickly, and soon aggression episodes started to decline. In part, the subordinate's yielding behavior appeared to discourage attack. The significance of the target bird's behavior on attack frequency was borne out by the finding in the SI test that pigeons attacked a shielded, live, active target more often than a passive one. Furthermore, using a specially constructed stuffed pigeon in the SI test, results indicated that programmed, combined aggressive vocalization and body movement evoked most attacks with the VT schedule, vocalization alone evoked the next highest number of attacks, body movement alone the third most, and combined silence and immobility the least attacks. These findings provide a basis for explaining some past reported results associated with target features and a means for selecting other target features for future study.     

Effects of imprinting and isolation on aggressive responses in chicks

The importance of isolation and imprinting as separate factors influencing early aggressive responses in chicks (Gallus gallus) was studied in two separate experiments. In addition the effect of the presence or absence of the imprinting stimulus in the test situation was examined in Experiment 1. Neither imprinting per se, nor the presence of the imprinting stimulus significantly affected aggressiveness. Rearing conditions (isolation vs social rearing) did, however, influence aggressive responses. Isolated chicks were significantly more aggressive than socially reared buds. The adaptedness of selective aggression in socially (naturally) reared chicks, as well as the indiscriminant aggressiveness caused by social deprivation is discussed.     

Aggressive reactions of ducklings to a nonliving target object

This study asked whether ducklings' forceful pecks at a nonliving target object could be validly identified as aggressive. Previously isolated ducklings were exposed to a small cylindrical object that could serve as a target for aggressive pecks and as an object for attachment. After initially attempting to flee from the target, they vigorously pecked at it and also showed signs of the formation of a social (imprinting) attachment. In all important respects this pattern of behavior was identical to the pattern of escape, aggressive pecks, and attachment seen when a previously isolated duckling first encounters a conspecific. Social housing, a manipulation which attenuates aggression against live targets in ducklings and other species, reduced pecking at the nonliving target object. Early aversive stimulation, which enhances aggression against live targets, increased pecking at the object. These findings support the use of nonliving targets in the study of aggression in ducklings.     

“Weapons effect” revisited: Motor effects of the reception of aversive stimulation and exposure to pictures of firearms

The effect of presenting images of firearms on the speed of clenching of the fist of human subjects simultaneously receiving an aversive stimulation was studied. It was thought that, whereas the classic interpersonal experimental situation confounds the effects of the stimulus presented and several interpersonal processes, speed of fist clenching in a noninterpersonal setting could constitute a valid measure of the subject's readiness to fight. Twenty-four male and 24 female students (ages > 20 and <36 years) were instructed to press with their right hand a device commanding the projection of slides upon reception of an acoustic signal. Speed of clenching of the hand was recorded in the four conditions generated by the combination of two levels of acoustic signal (aversive and nonaversive) and two modalities of slides (firearms or tools). The results show that the reception of aversive sound accelerates fist clenching. Simultaneous presentation of slides of firearms and reception of aversive noise increases the speed of clenching of the fist. The slides' main effect was not significant. More irritable subjects tend to execute this movement faster than their less irritable counterparts, and more emotionally susceptible subjects tend to be slower than less susceptible ones. Male subjects were faster than females. This pattern of results is discussed in relation to the hypothesis formulated by the authors.     

Concurrent and predictive validity of self-reported aggressiveness

The subjects (60 boys) were drawn from the sample of a longitudinal study of social development and represented extremely aggressive, anxious, constructive, and submissive behaviour at the age of 8. They were presented with three question series concerning (1) their responses to aggressive attacks; (2) reactions in frustration situations presented in short stories; and (3) their aggressive initiatives. In each series the type of aggressive behaviour, attacker, victim, and other situational factors were systematically varied. In series 2 the type of response, open-ended or forced-choice, was also varied. The results showed that the most valid way of studying boys' self-observations on their aggressive behaviour was to ask if they attack somebody without a specific reason (series 3). This correlated with contemporaneous overt aggression at the age of 8 and predicted aggressiveness and various characteristics of antisocial aggressive development at the ages of 14 and 19. Self-observations on one's physical aggression were more valid for ratings of overt aggressiveness than on verbal aggression. The open-ended or forced-choice type of response did not affect the validity of aggressive responses. Of the categories of nonaggression, ‘conciliatory responses’ had the highest concurrent and predictive validity for constructiveness and other indicators of strong self-control.     

Behavioral changes over several successful agonistic encounters between male mice: Effects of type of “standard opponent”

This study assessed whether two types of non-aggressive “standard opponents” (“intact” and “anosmic” group-housed males) produced similar behavioral changes in isolated OF1 male mice given several experiences of victory. Experimental groups confronted either intact or anosmic opponents every two days until they had completed four encounters. The behavioral changes were recorded using a detailed ethologically inspired analysis. These changes were clearly different depending on the opponent type. When intact opponents were used, experimental subjects increased the time spent in digging, non-social exploration, explore from a distance, and attack over encounters, but showed decreased time spent in threat and a decreased latency to the first attack. In encounters with anosmic opponents, only declines in the latencies to threat and attack were noted. Moreover, the experimental groups differed in their behaviors over encounters. Those confronting intact opponents spent less time in social investigation, more time in explore from a distance and threat, and showed a shorter latencies to threat and attack than counterparts confronting anosmics. These results suggest that, although both types of “standard opponents” are similar in their non-aggressiveness, they elicit rather different behavioral responses in their adversaries. These findings provide additional support for the view that the type of opponent used in studies on intermale aggression is of paramount importance. Indeed, the use of different types of “standardized non-aggressive opponents” appears to be an important source of variability between studies. © 1994 Wiley-Liss, Inc.     

Dominance-subordinance in cohabiting pairs of adult rats: Effects on Aggressive behavior

Following an initial intruder aggression test, 10 pairs of adult male rats matched on aggressiveness were formed. The first 20 min of paired cohabitation were used to determine dominance and subordinance between pau members. Residents judged to be dominant from this observation session gained significantly more weight during cohabitation and exhibited significantly more aggression on the second aggression test than their subordinate counterparts. Significant correlations among various measures of aggression were found, but open field performance did not correlate, with the measures of aggression nor did changes in open field scores reflect changes in aggression.     

Inheritance of dominance and aggressiveness in captive red grouse Lagopus Lagopus scoticus

Sibling red grouse resembled each other and their parents in social dominance rank and in an aggressiveness score. This was shown by comparisons of variance within and among clutches, correlations between parents and offspring, and experiments involving selection. Both dominance and aggressiveness scores were inherited. There was weak evidence that a laying hen's nutrition and crowding might also influence the dominance of her offspring. These results indicate mechanisms that may underlie fluctuations in the numbers of wild red grouse.     

Differences between two strains of mice,selectively bred for high and low aggressiveness,in the capacity of male odors to affect aggressive behavior

The connection between a genetic disposition for aggressive behavior and the odor signal system in male mice was studied. The males belonged to two strains of mice which have been developed by selective breeding for high- (TA) and low aggressiveness (TNA). Urine from the high aggressive strain (TA), when applied to castrates, stimulated the aggressiveness of NMRI males while TA-soiled bedding suppressed their aggressiveness. In response to male odors from the low aggressive strain (TNA), the NMRI males showed quite contrasting reactions. The results provide evidences of a correlation between the hereditarily determined disposition for aggressive behavior and the odor signal system in TA- and TNA males.     

Attack by female mice on “Strangers”

In this study the aggressive responses directed by small groups of female mice towards virgin, pregnant, and lactating female strangers, which were individually introduced into their cages, were compared. The results obtained show that, except when lactating, pregnant females are neither attacked much more often nor any more severely than virgin mice. It is suggested that only the state of lactation favors the production of stimuli (olfactory) which release attack by female mice.     

Personality correlates of revenge‐seeking: Multidimensional links to physical aggression,impulsivity, and aggressive pleasure

People differ in how much they seek retribution for interpersonal insults, slights, rejections, and other antagonistic actions. Identifying individuals who are most prone towards such revenge‐seeking is a theoretically‐informative and potentially violence‐reducing endeavor. However, we have yet to understand the extent to which revenge‐seeking individuals exhibit specific features of aggressiveness, impulsivity, and what motivates their hunt for retribution. Toward this end, we conducted three studies (total N = 673), in which revenge‐seeking was measured alongside these other constructs. Analyses repeatedly demonstrated that revenge‐seeking was associated with greater physical (but not verbal) aggressiveness, anger, and hostility. Revenge‐seeking's link to physical aggression was partially accounted for by impulses toward enjoying aggression and the tendency to use aggression to improve mood. Dominance analyses revealed that sadism explained the most variance in revenge‐seeking. Revenge‐seeking was associated with greater impulsive responses to negative and positive affect, as well as greater premeditation of behavior. These findings paint a picture of revenge‐seekers as physically aggressive curators of anger, whose retributive acts are performed with planned malice and motivated by the act's entertaining and therapeutic qualities.

     

Attributions for social failure and adolescent aggression

In the present study, 119 high school boys and 79 institutionalized delinquent boys of the same age range were assessed on their own aggressive behavior and on their tendencies to attribute social failure to controllable, external, stable causes, anticipate a hostile affective response, and endorse aggressive behavioral responses to by pothetical social situations. While the two populations of boys did not differ detectably in their attributional tendencies, the relations between an individual's aggressiveness and an individual's attributions differed considerably across the two populations. In particular, among deliquent but not among delinquent but not among nondelinquent boys, the tendency to attribute one's social failures to stable and controllable causes predicted stronger hostile emotional responses to failure and a tendency to endorse physically aggressive responses following such failure. These hostile emotional responses to failure and this preference for a physically aggressive response, in turn, predicted greater actual aggression within the population of delinquent boys. Neither of these links could be demonstrated for nondelinquent boys. However, in the nondelinquent sample, attributing social failure to external and controllable causes predicted endorsement of aggressive responses only indirectly through increased hostile affect. It was concluded that the specific relations between cognitive and affective responses to social failure may be a contributing factor to the serious physical aggression displayed by some delinquents and to the less serious aggression of nondelinquents. © 1993 Wiley-Liss, Inc.     

Aggressiveness and dominance in captive cock red grouse

A method for measuring the aggressiveness of captive cock red grouse is described. A cock's aggressiveness varied according to season, type of cage and social environment. A method for ranking the dominance order of cocks in a group is also described. Dominance ranks remained stable for up to two years. Correlations between the aggressiveness of isolated cocks and their dominance ranks when in a group were positive but weak. Aggressiveness and dominance should be clearly distinguished. Both aggressiveness and dominance were related to the size of cock's combs, and implants of testosterone increased all three. In situations where a cock's aggressiveness changed, comb size changed in the same direction. The aggressive behaviour of captive cocks shows several major parallels with that of wild cocks.     

“We're not friends anymore! unless…”: the frequency and harmfulness of indirect,relational, and social aggression

The frequency of items of indirect, relational, social, verbal, and physical aggression was assessed in the school environment of 422 adolescents, using the Indirect/Social/Relational Aggression scale (ISRA), a measure that combined items from indirect, relational, and social aggression research. We also assessed the perceived harmfulness of each item. Comparing these findings with the occurrence of aggression on television, we found that adolescents were exposed to nearly 10 times more indirect, relational, and social aggression on television than they are in school. Overall, there was no sex difference in the amount of aggression reported by boys and girls. However, when examining specific items, girls reported more gossiping and boys more hitting. Girls perceived indirect, direct relational, and verbal aggression as more harmful than did boys. Limited evidence was found for a distinction between indirect, relational, and social aggression, although it was clear that they were more similar than different. Aggr. Behav. 32:1–14, 2006. © 2006 Wiley‐Liss, Inc.     

Pictorial target control of schedule-induced attack in White Carneaux pigeons

Three pigeons with a history of attacking a mirror target, and two of six pigeons with no prior exposure to targets, attacked a colored photograph of a conspecific during exposure to intermittent schedules of reinforcement for key pecking. Rate of attack on the photograph decreased when the reinforcement schedule was removed. The topography, temporal pattern, and locus of attack on the picture were comparable to schedule-induced attack on live, stuffed, and mirror targets. When silhouette, outline, and plain paper targets were used, schedule-induced attack was more sensitive to a change in target characteristics with a concurrent target-preference procedure than with an analogous successive-testing procedure. The combined results of the two testing procedures indicated that an “upright” white-on-black silhouette of a pigeon with or without an eye was more effective in controlling attack than was a comparable “inverted” silhouette, an outline of a pigeon, or a piece of colored paper.     

The influence of the victim on shock induced aggression in rats.

In two studies, free-roaming male rats (aggressors) were shocked in the presence of male target rats restrained in either an upright or a supine posure. In addition, in Experiment II, two levels of aggressor shock intensity (0.8 mA or 2.0 mA) were used while targets received one of three levels of shock (0.5 mA, 1.5 mA, or 2.5 mA). In both studies, upright targets were attacked less than supine targets. Frequency of aggression was directly related to level of aggressor shock intensity in Experiment II. Also, attack by 0.8-mA aggressors against supine targets was inversely related to level of target shock intensity. The low level of attack against upright targets was interpreted in terms of a threat diaplay. Similarily, it was concluded that the target shock-intensity effect in Experiment II was due to specific threat behaviors displayed by those supine rats that received the highest-intensity shocks.     

It's not just what you say,it's how you say it too. Adolescents' hostile attribution of intent and emotional responses to social comments

A highly prevalent and relevant situation in which adolescents have to interpret the intentions of others is when they interact with peers. We therefore successfully introduced a new paradigm to measure hostile attribution bias (HAB) and emotional responses to such social interactions and examined how it related to youth's aggressiveness. We presented 881 adolescents (M_age = 14.35 years; SD = 1.23; 48.1% male) with audio fragments of age-mates expressing social comments that varied in content (e.g., what the person says) and tone of voice (e.g., how the person says it). Participants' peers also reported on their aggressiveness. In general, added negativity of content and tone was driving the youth's intent attribution and emotional responses to the comments. In line with the Social Information Processing model, we found more hostile attribution of intent and more negative emotional responses of aggressive youth to ambiguous stimuli. Aggression was also related to more hostile intent attributions when both content and tone were negative. Unlike most studies on HAB, the aggression effects in the current study emerged for girls, but not boys. Implications of these results and future use of the experimental paradigm are discussed.     

The decline of aggressiveness in male mice during group caging as determined by punishment delivered by the cage mates

Group-housed rodents are generally less aggressive than isolated counterparts. The present study examined the role of defeat by cage mates as a reason for this decline in aggressiveness. In Experiment I, highly aggressive isolated male mice were introduced into aggressive or nonaggressive resident groups. The intruder's level of aggressiveness directed toward a group-housed standard opponent declined more rapidly after daily exposure to the aggressive than to the nonaggressive groups. Intruders in the aggressive groups received more attacks from their cage mates, and delivered fewer attacks to them than did the intruders in the nonaggressive groups. In Experiment II, the intruders lived for seven days in small wire net cages in the middle of the group cages. Their level of aggressiveness toward standard opponents decreased little during the preexposure but after being put freely into the groups, their aggressiveness declined to a minimal level within a day. Experiment III showed that when the wire net protection in the middle of the cage was installed after the group caging experience, the aggressiveness of the intruders did not return to the isolation level as effectively as it did in isolation. This is explained by the aggression-inhibiting content that the cues from the cage mates have acquired during group caging. The decline of aggressiveness in male mice during group caging is determined by punishment delivered by the cage mates.