Inhibition of aggression by progesterone and its metabolites in female Syrian hamsters

The sequence of estradiol and progesterone is known to inhibit the expression of aggression in female hamsters. Despite the key importance of progesterone in the inhibition of aggression, little is known of the mechanisms through which progesterone may exert this effect. Three experiments were performed to assess the degree to which metabolites of progesterone can affect aggression in female Syrian hamsters. Systemic estradiol treatment followed by injections of either progesterone (300 μg IP) or 4‐pregnen‐21‐ol‐3,20‐dione (DOC, 300 μg IP) reliably inhibited aggression. Systemic injection (75, 150, or 300 μg IP) of either 5α‐pregnan‐3α,21‐diol‐20‐one (THDOC) or 5α‐pregnan‐3α‐ol‐20‐one (3α,5α‐THP) did not affect aggression. Intracerebroventricular infusion of 3α,5α‐THP following systemic estradiol treatment also did not affect aggression. In a third experiment, female hamsters were given systemic treatments with estradiol and progesterone that were subthreshold with respect to inhibition of aggression. In these females, intracerebroventricular infusion of THDOC inhibited aggression. These results indicate that metabolites of progesterone can inhibit aggression, most notably in synergy with progesterone itself. Aggr. Behav. 27:372–381, 2001. © 2001 Wiley‐Liss, Inc.     

Personal and participatory socializers of the perceived legitimacy of aggressive behavior in sport

Recent international attention from the media and professional organizations has focused increasingly on violent incidents in sport. The present study developed and used the Sport Behavior Inventory (SBI) to examine personal and participatory variables that influence the socialization of the perceived legitimacy of aggressive sport behavior in children and adolescents ages 8–19 enrolled in public schools. In phase I of this study, the psychometric properties of the SBI as a measure of perceived legitimacy were evaluated in terms of content validity, structural validity, internal consistency, convergent validity, and discriminant validity. A multiple regression analysis in phase II indicated that increases in athletes’ perceptions of the legitimacy of aggressive sport behavior were positively related to age, being male, and contact sport participation. Results were discussed in relation to the social factors that contribute to the development of perceptions of legitimacy for aggressive sport behavior, and future research uses for the SBI. Aggr. Behav. 27:405–418, 2001. © 2001 Wiley‐Liss, Inc.     

Cultural and sex differences in aggression: A comparison between Japanese and Spanish students using two different inventories

Two self‐report inventories developed to assess different dimensions of aggression, the Aggression Questionnaire and the EXPAGG, were administered to a sample (N = 400) of men and women undergraduates in two Japanese and Spanish universities. The factor structure of scales was assessed using exploratory factor analysis. Both questionnaires showed high correlations between their respective scales. In both cultures, males reported more physical aggression, verbal aggression, and hostility as well as higher instrumental beliefs, whereas females reported more expressive representation than males. Japanese students reported more physical aggression than their Spanish counterparts, who reported more verbal aggression, hostility, and anger and more expressive representation of aggression. Aggr. Behav. 27:313–322, 2001. © 2001 Wiley‐Liss, Inc.     

Vengeance: Effects of gender,age, and religious background

Vengeance can be commonly defined as the infliction of harm in return for perceived injury or insult or as simply getting back at another person. Three hundred fifty‐three participants responded to eight hypothetical scenarios that may elicit vengeful behavior in which the offending party was either a romantic partner, a friend, a coworker, or a stranger. Participants also completed a vengeance scale and a measure of biblical literalism. Participants were most vengeful toward coworkers and least vengeful toward romantic partners. Age, religious conservatism, and gender were significant predictors of attitudes toward vengeance. Although men were more likely than women to be accepting of vengeful attitudes as measured by the vengeance scale, only age was a significant predictor of behavior in the vengeance scenarios. The current research provides a basis for a systematic investigation of vengeance within the structure of human relationships and interactions. Aggr. Behav. 27:343–350, 2001. © 2001 Wiley‐Liss, Inc.     

Antecedent manipulations in a tangible condition: effects of stimulus preference on aggression.

After a functional analysis indicated that aggression of an 8‐year‐old boy with autism was maintained by access to preferred items, antecedent manipulations involving the relative preference of restricted and noncontingently available stimuli were conducted. Restricting highly preferred items evoked the highest rates of aggression regardless of the preference level of the noncontingently available alternative items. Restricting less preferred stimuli was associated with moderate rates of aggression even when the alternative items were more preferred.     

Conspecific aggression influences food carrying: Studies on a wild population of Rattus norvegicus

Laboratory rats, like many other animal species, transport food. Their behavior is influenced by factors such as food size, the time required to eat, travel distance, travel difficulty, and the availability of cover, etc. Recent versions of optimal foraging theory suggest that species that display such behavioral patterns do so in order to minimize risk to predation while at the same time maximizing food gain. Nevertheless, it is not clear that this explanation applies to rats, nor is it easy to investigate this problem in a laboratory. The results of the present study on urban feral rats show that their food handling behavior is similar to that of domestic rats. The results also suggest that food carrying can serve defensive as well as communicative functions. Aggression around food sources was high. Smaller rats always carried food and some large rats infrequently carried food, suggesting that the food carrying by smaller, subordinate rats may help them avoid conspecific aggression. The rats also vigorously attempted to steal food that was carried home by conspecifics. This result suggests that food carrying can redistribute food resources and inform conspecifics about food availability. The results demonstrate the utility of multilevel behavioral analysis and also demonstrate that for rats, food transport has functions other than predator avoidance, including avoidance of conspecific aggression and communication about food availability. © 1996 Wiley-Liss, Inc.     

Fallow deer tactic to compete over food with red deer

Small ungulates may compete with larger species through higher mobility, greater aggressiveness, and/or by larger group sizes. We observed a herd of approximately 100 red deer (Cervus elaphus) and 130 fallow deer (Dama dama) at the Žehušice Deer Park during supplemental feeding to determine whether fallow deer can displace red deer at feeding sites and to describe strategies used for displacement. Data were analyzed during the antlered period (AP) when males of both species had hard antlers and the cast period (CP) when all red deer stags had cast antlers, but fallow bucks were still in a hard antler. We conducted 41 observation sessions, 29 during the AP and 12 during the CP. In both periods red deer were more numerous than fallow deer at the feeding sites. Fallow bucks initially waited until red deer arrived at the feeding site, after which they attacked any red deer. Fallow bucks were more aggressive than red deer stags or hinds. When stags retaliated, the bucks turned their attacks toward hinds. During feeding sessions, attacks against hinds intensified, while bucks avoided encounters with stags. As a result, in most cases (90%), red deer vacated the feeding site before the supplementary food was depleted. In contrast, fallow does not compete with the larger red deer and selected other sources of food in the park. © 1996 Wiley-Liss, Inc.     

On the dual nature of maternal aggression in rats

Presentation of a natural predator, a cat, was used to differentiate elements of maternal attack by female rats on a male intruder. Following exposure (without direct physical contact) of post-partum females to a cat or to a toy stuffed cat (control group), the females were replaced in their home cages and presented with a male intruder rat. Cat exposure reliably decreased lateral attack to the intruder, as well as locomotion, but had no effect on either jump attack or an upright defensive posture (boxing). Since predator exposure produces a somewhat durable increase in defense, along with inhibition of nondefensive behavior, these results suggest that maternal aggression represents a mixture of offensive, usually related to competition, and defensive (protective) behaviors. The results indicate that maternal aggression, as a parental care behavior, appears to be at least partially resistant to fear. © 1996 Wiley-Liss, Inc.     

Life spans in mice from strains selected for high or low aggression

The present study assessed the life spans in two lines of mice selectively bred for high (Turku Aggressive, TA) and low (Turku Nonaggressive, TNA) levels of aggression. The maintained parental Swiss albino strain (N), normally distributed with regard to aggression, served as a control line. It was found that the TNA males had a significantly shorter life span than the other lines of mice of both sexes. The relative early death of the TNA males was discussed in terms of male age-related decline of inherited low levels of catecholamine and androgenous hormone concentrations. © 1996 Wiley-Liss, Inc.