CHANGES IN THE AGGRESSIVENESS OF MICE RESULTING FROM SELECTIVE BREEDING, LEARNING AND SOCIAL ISOLATION

LAGERSPETZ, K. M. J. & LAGERSPETZ, K. Y. H. Changes in the aggressiveness of mice resulting from selective breeding, learning and social isolation. Scand. J. Psychol. 1971, 12, 241–248.–Selective breeding for aggressiveness and non-aggressiveness in mice has now been going on for 19 generations. The aggressiveness score distributions of the males have not changed since the 7th generation. Socially naive male mice which had been living in isolation, had five encounters with submissive males, and five with receptive females. Learning of aggressive and sexual behaviour occurred in males of both the aggressive and the non-aggessive strain. When living in groups, the males of both strains show no aggressiveness towards a submissive opponent. Social isolation for 1–2 weeks greatly increases the aggressiveness level of the animals of the aggressive strain. The effects of grouping is interpreted as social learning of non-aggressive behaviour, the effect of isolation as return of the inter-individually variable aggressiveness level, determined by genetic variation and early experience. Some neurochemical findings are in agreement with the observed behavioural effects.     

THE EFFECT OF PRIOR AGGRESSIVE OR SEXUAL AROUSAL ON SUBSEQUENT AGGRESSIVE OR SEXUAL REACTIONS IN MALE MICE

Previous aggressive behaviour towards a male mouse was found to decrease sexual behaviour of inexperienced male mice towards a female in heat, mainly due to aggressive behaviour occurring in the sexual situation. Sexual behaviour decreased the aggression displayed in a subsequent encounter with a male. Instead, homosexual behaviour occurred in the situation with the male. After either sexual or aggressive behaviour had been practised, it was no longer influenced by practice of the other activity. Inhibition of aggressive behaviour by successive defeats did not affect sexual performance.     

THE EFFECTS OF CONFLICT AND STRESS ON SEXUAL AND AGGRESSIVE BEHAVIOUR IN MALE MICE

LAGERSPETZ, K. & HYVARINEN, S. The effects of conflict and stress on sexual and aggressive behaviour in male mice. Scand. J. Psychol. , 1071, 12, 119–127. –A conflict consisting in a conditioned response performed in order to drink, coupled with electric shocks, did not affect aggressive and sexual behaviour in a neutral environment. Conditioning only or shocks only also did not have any effects. When tested in the shuttle box, the groups showed differences in behaviour. A generally higher level of activation was shown by the experimental groups. The results are discussed in terms of the concept of 'experimental neurosis'.     

The expression of the genes of aggressiveness in mice: The effect of androgen on aggression and sexual behavior in females

Female mice of strains selectively bred for aggressiveness or nonaggressiveness were injected with testosterone propionate (TF′) at the age of 2 days and as adults, or they were injected as adults only. Aggressive and sexual behavior was then tested with female, receptive female, and male partners before, during, and after the latter TP treatment. The females that had received both TP treatments displayed as much or as little aggression as males of the same strain, leading to the conclusion that aggressiveness genes are not linked with the male sex chromosome, even though they depend on it for their expression. The sexual behavior of the females of both strains that had received both TP treatments was altered to the male type. In the females of the aggressive strain even adult treatment alone was sufficient for this change. Aggressiveness and male sexual behavior would seem to be determined separately, although aggressiveness facilitates the display of male sexual behavior.     

Effects of early exposure to mating on adult sexual behavior in male mice varying in their genetic disposition for aggressive behavior

This study examined whether the sexual behavior of adult male mice is influenced by exposure in early postnatal life to brief episodes of mating. Another focus of interest was the interplay between a genetic disposition for aggressive behavior and the early exposure experiences. The subjects used in the study were male mice of the fiftysixth generation of selection for high (Turku aggressive, TA) and low (Turku non-aggressive, TNA) levels of aggressiveness. Moderately aggressive males of the parental strain (normal, N) were also used. Subjects of each strain were exposed from 21 to 32 days of age to mating mice behind a wire mesh screen. Control subjects were placed in a comparable enclosure, but were exposed to nothing. The results showed that male mice exposed to mating early in life showed a higher rate of activities in the sexuality tests, including aggressive responses. A genetic potential for aggressive behavior was related to a higher degree of sexual activity, and the early exposures optimized the hereditary attributes. The relation between sexual and aggressive behavior is discussed. © 1994 Wiley-Liss, Inc.     

GENETIC AND SOCIAL CAUSES OF AGGRESSIVE BEHAVIOUR IN MICE

L agerspetz , K irsti . Genetic and social causes of aggressive behaviour in mice. Scand. J. Psychol ., 1961, 2 , 167—-173.—Significant differences in the aggressiveness of mice selected for aggressiveness and non-aggressiveness have been found to occur in the 2nd and 3rd generation of selective breeding. In S _a, motor activity scores were significantly higher in mice of the aggressive than of the non-aggressive strain. Defecation and ambulation scores obtained both in a standardized open-field test and in connection with the aggression measurements showed that the S₃ descendants of the aggressive mice were emotionally less reactive than the members of the 3rd non-aggressive generation. Defeats tend to decrease, victories to increase the level of aggressiveness in mice, but the aggression scores tend to return to the original level after the termination of the experiments.     

NEUROCHEMICAL AND ENDOCRINOLOGICAL STUDIES OF MICE SELECTIVELY BRED FOR AGGRESSIVENESS

L agerspetz , K. Y. H., T irri , R. & L agerspetz , K. M. J. Neurochemical and endocrinological studies of mice selectively bred for aggressiveness. Scand.J. Psychol ., 1968, g, 157–160.—Several neurochemical and endocrinological variables were studied in male albino mice from two strains, selectively bred for aggressiveness and non-aggressiveness. Differences were found in the weight and the serotonin content of the forebrain, in the catecholamine contents of the brain stem and of the adrenal gland as well as in the weight of the testis. The results indicate that mice selectively bred for aggressiveness show physiological signs of higher orthosympathetic activity than the mice selectively bred for non-aggressiveness.     

The female sexual delinquent]

Among 371 adult sexual delinquents, there were only 14 women. From a total of 16 female sexual delinquents, 9 were feeble-minded, 4 mentally disabled, 3 were physically disabled, and almost all were uneducated and solitary people. The personality was distinguished by emotional disturbances, unsteadiness, impulsiveness, and often anti-social behaviour. Only in the cases of incest between brother and sister were cases of inhibited female character discovered. Among others, 3 cases of sexual crimes against children, and one case of probable fetishism are presented. Traditional moral inhibitions, passivity and an extensive lack of aggressiveness in the sexual behavior of woman, together with a stronger mental link between eroticism and sexuality than with the male, are seen as the main causes for the low figure of female sexual delinquents.     

The relationship between aggressive and sexual behavior in male mice: Effects of testosterone and parachlorophenylalanine

The purpose of this study was to clarify the connection between aggressive and sexual behavior with the aid of testosterone propionate (TP) and parachlorophenylalanine (PCPA). Previous studies have indicated that aggressive and sexual behavior are positively correlated, and it has been suggested that both behaviors are related to the level of general arousal. Testosterone has documented effects on both aggressive and sexual behavior. It has been hypothesized that these effects are due to an increased level of general arousal. If this is the case, aggressive and sexual behavior could be restored by administration of drugs excitating the central nervous system, e.g., PCPA. The present study examined the effects of TP and PCPA on aggressive and sexual behavior in gonadectomized male mice. Control animals were injected with sesame seed oil or saline. The level of aggressiveness was assessed by means of dyadic tests with gonad-intact male opponents. For the sexuality tests, a receptive female was placed in the home cage of the experimental male. The results showed that male mice injected with PCPA were more aggressive than the males of the other groups, while the TP-exposed males expressed the most sexual activity. Compared to the control group, the PCPA and TP groups were more active in both the aggression and the sexuality tests. These findings lend support to the hypothesis that the earlier documented correlations between aggressive and sexual behavior could be due to both behaviors being dependent on a certain level of general activation. Aggr. Behav. 24:367–377, 1998. © 1998 Wiley-Liss, Inc.     

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.     

Effects of clean and soiled sawdust substrates and of different urine types upon aggressive behavior in male mice

The effects of sawdust taken from the cages of grouped or isolated male mice upon the aggressiveness of trained fighter mice toward castrated opponents were examined. The results indicate that (1) substrate soiled by stable groups of male mice does not provide aggression-promoting odors, (2) application of the urine of isolate male mice to castrate opponents increases the aggressiveness of fighters toward the castrates, and (3) application of isolate male urine to the test substrate inhibits the aggressive behavior of a fighter toward its castrated opponent. The concepts that male mouse urine possesses both aggression-promoting and aggression-inhibiting cues are not mutually exclusive, but the action of the urine depends upon whether it is placed onto a mouse or onto the substrate. The findings are discussed in relation to those of previous studies on soiled sawdust and aggression, and an attempt is made to relate these results to a territorial situation.     

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.     

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.     

Personality and reciprocal inhibition theory: The link between aggression and sexual reactivity

The study tries to relate two approaches often discussed in the context of aggression and violence in combination with sexual arousal, the reciprocal inhibition theory (Wolpe, 1958) and an approach from personality psychology which emphasizes the psychoticism dimension (P) according to Eysenck and Eysenck (1975) as a mediator of violent sexual offence. The effects of preexposure to a violent vs. neutral movie on sexual reactivity to violent and non-violent sexual stimuli (audioplays and pictures) was studied in a male student population (N=64). Sexual reactivity was measured by self-ratings, inspection time and electrodermal activity. Results could not confirm reciprocal inhibition theory but revealed that sexual reactivity for subjects scoring high vs. low on the psychoticism/aggressiveness dimension were differently affected by preexposure to violence.     

Effects of early exposure to intermale aggression on the aggressiveness of adult male mice varying in their genetic disposition for aggressive behavior

This study examined whether adult male aggression is influenced by either visual or olfactory exposure in early postnatal life to brief episodes of aggression. Another focus of interest was the interplay between a genetic disposition for aggressive behavior and early exposure experiences. The subjects used in the study were male mice of the 49th generation of selection for high (Turku Aggressive, TA) and low (Turku Non-Aggressive, TNA) levels of aggressiveness. Moderately aggressive males of the parental strain (Normal, N) were also used. Subjects of each strain were exposed from 21 to 32 days of age to fighting males either behind a wire mesh or glass screen. Control subjects were isolated during the entire experimental period. At 90–100 days of age, each subjects was tested three times for its aggressiveness. Exposure to fighting males behind a wire mesh screen enhanced later aggressiveness of juvenile male mice. Juveniles exposed solely to visual cues were comparable to isolates, both groups showing less adult aggression. Early experience and the genetic disposition for aggression were correlated; TA males showing the greatest increase in aggressive behavior. The role of early olfactory learning is discussed. © 1993 Wiley-Liss, Inc.     

ADOLESCENTS' SEXUAL INFERENCES ABOUT GIRLS WHO CONSUME ALCOHOL

The purpose of this study was to document whether adolescents make inferences regarding male and female vignette characters in terms of the characters' sexuality, social skills, impairment, and aggressiveness when the characters consume alcohol. A Web-based survey of 1,691 middle and high school students (grades 6–11) from diverse socioeconomic and ethnic backgrounds was conducted. The Dating Vignette and Subjective Perception Form ( George, Gournic, & McAfee, 1988 ) were modified for use with an adolescent sample and embedded within the Web-based survey. There were significant interaction effects between the male and female characters' alcohol consumption in terms of the respondents' perception of the female character for all of the subscales examined (i.e., sexual disinhibition, social skills, impairment, and aggressiveness). In contrast, there were no significant interactions between the characters' drinking and the respondents' perception of the male character. Collectively, these findings suggest that adolescents' perceptions of girls are based not only on the girls' own drinking behaviors, but also their male partners' drinking behaviors.     

UNWANTED INTERCOURSE: THE DIFFICULTY OF SAYING NO

Unwanted intercourse occurs when a reluctant partner is induced to acquiesce against her (his) will by psychological pressure from the would-be lover, but without the use of or the threat of force. An earlier study found that 30% of a representative probability sample of senior women in a liberal arts college had experienced unwanted intercourse. College women's ( N = 76 ) perceptions of the unwanted intercourse situation were assessed by projective and by questionnaire methods, using a videotaped stimulus cue. Results indicate that highly negative feelings are attributed to the man in the refuse situation, and to the majority of the women in both the accept and refuse situations. A hedonic calculus analysis based on the ratio of negative to positive feelings in the stories demonstrates the cost-benefit superiority of accepting unwanted intercourse in spite of the fact that the women's feelings are predominantly negative. A theory of unwanted intercourse is proposed that attributes the high rate of unwanted intercourse to four societal norms: (a) current remnants of the ideology of male supremacy, (b) the norm of male initiative, (c) the lack of positive sexual experience norms for women, and (d) the "stroking norm" for women.     

A LABORATORY ANALOGUE FOR THE STUDY OF PEER SEXUAL HARASSMENT

The purpose of this study was to develop a laboratory analogue for the study of peer sexual harassment, and to examine person and situational factors associated with male on female peer sexual harassment. One hundred twenty-two male participants were given the opportunity to tell jokes to a female confederate from a joke list that included sexually offensive jokes, as well as other types of jokes. Participants were exposed to either a sexist laboratory environment or a neutral laboratory environment during the study. Eighty percent of participants told at least one sexually offensive joke to a female confederate. Higher scores on a measure of adversarial sexual beliefs were associated with telling a greater number of sexually offensive jokes. The results suggest that the joke-telling analogue may be a useful means for laboratory explorations of person and situational factors associated with peer sexual harassment.     

Interspecific aggressiveness and reactivity in mouse-killing and nonkilling rats: Compared effects of olfactory bulb removal and raphe lesions

The experiments aimed at uncovering possible correlations between inter-specific aggressiveness and general and emotional responsiveness (appraised by means of the open-field technique) in the rat. Killer rats showed a higher level of emotional responsiveness than nonkillers. Removal of the olfactory bulbs induced an increased reactivity both in the rats which were converted into killers in those whose behavior toward mice remained unchanged. Destruction of the dorsal and medial nuclei of the raphé induced a clear hyperreactivity in most lesioned animals, but provoked initiation of mouse-killing behavior in only one-third. When produced in rats which had remained nonkillers following olfactory bulb removal, the raphé lesion clearly enhanced both the general and the emotional responsiveness; it provoked initiation of mouse-killing behavior in about 75% of the lesioned animals. The discussion bears on the correlations between interspecific aggressiveness and experimentally induced hyperreactivity in the rat.     

Perceiving Aggression from Facial Structure: Further Evidence for a Positive Association with Facial Width‐to‐Height Ratio and Masculinity,but not for Moderation by Self‐Reported Dominance

Recent work has indicated that individual differences in facial structure are linked to perceptions of aggressiveness. In particular, the relative width of a face [facial width‐to‐height ratio (fWHR)] has been suggested to be a reliable cue to aggressive behaviour, at least in men. Additionally, facial masculinity has been associated with perceptions of dominance, a close proxy of aggressiveness. In two studies, we assessed the robustness of this link using faces transformed along these vectors in men (Studies 1 and 2) and women (Study 2). Additionally, we examined whether individual differences in self‐reported dominance of perceivers moderated this association in order to extend previous work indicating that own dominance affects perception of such behaviour in others. Results indicated that both male and female faces with increased fWHR and increased facial masculinity were perceived as more aggressive. However, we found no systematic evidence for moderating effects of self‐reported dominance on the perception of aggression in others. Taken together, these results further support the robustness of fWHR and facial masculinity as cues to aggressiveness but question whether observers' own dominance moderates their perception of these cues in others. Copyright © 2013 European Association of Personality Psychology