Maternal territoriality as an offspring defense strategy in red swamp crayfish (Procambarus clarkii,Girard)

The offspring‐defense hypothesis of maternal territoriality in solitary and semisocial mammals [Wolff JO and Peterson JA. 1998. Ethol Ecol Evol 10:227–239] was evaluated in another taxon using maternal and nonmaternal female red swamp crayfish (Procambarus clarkii), a freshwater decapod crustacean that shows pronounced shelter‐related maternal aggression. The maternal females were of three different categories: (1) ovigerous, (2) carrying primarily stage 1 offspring, or (3) tending offspring that were primarily stage 2. Each female was in residence in an individual aquarium containing only a gravel substrate for 24 hr prior to serial intrusions by male conspecifics. Virtually all of the residents, maternal and nonmaternal, excavated a depression (shelter) in the substrate prior to the first intrusion. The results showed that residents in each of the maternal categories won a significantly higher proportion of their encounters than did the nonmaternal residents, which showed only negligible defense and lost every encounter. However, there were no significant differences in encounter outcomes between the maternal resident categories. There was clear defense of the shelter by maternal females, with virtually all fighting being in or around it, thus demonstrating stable, heightened territorial defense throughout these maternal phases of reproduction. This support of the offspring‐defense hypothesis of maternal territoriality is the first such evidence for a freshwater crustacean and is very similar to that recently reported in a related marine decapod, the American lobster (H. americanus). Aggr. Behav. 27:391–403, 2001. © 2001 Wiley‐Liss, Inc.     

Selection for reduced aggressiveness towards man and dopaminergic activity in Norway rats

The brain dopaminergic system is involved in the process of long-term selection for reduced aggressive reaction towards man in Norway rats. The dopamine levels in the striatum as well as the nucleus accumbens with the tuberculum olfactorium were significantly lower in domesticated rats than in their wild counterparts. A substantial decrease was found in homovanillic acid level in the n. accumbens and tuberculum olfactorium. Specific binding of [³H]spiperone which labels D-2 dopamine receptors was higher in the mesolimbic structure of tame rats, whereas binding of [³H]SCH 23390 (D-1 receptors) was unchanged in this area. No substantial differences were detected in D-1 and D-2 binding in striatum. Apomorphine (0.3 mg/kg) elicited less locomotion in tame animals, reflecting a decrease of sensitivity of postsynaptic dopamine receptors. Tame rats showed fewer aggressive contacts in a foot-shock test than wild rats and the D-2 receptor antagonist sulpiride (25 mg/kg) significantly decreased the foot-shock aggression only in wild rats. Therefore, domestication, which diminishes defensive behavior and emotional reactivity of animals, is associated with decreases of dopamine level in the striatum, changed metabolism of dopamine in mesolimbic system, and an alteration in density and senstivity of D-2 receptors.     

Media violence, physical aggression, and relational aggression in school age children: a short-term longitudinal study

Many studies have shown that media violence has an effect on children's subsequent aggression. This study expands upon previous research in three directions: (1) by examining several subtypes of aggression (verbal, relational, and physical), (2) by measuring media violence exposure (MVE) across three types of media, and (3) by measuring MVE and aggressive/prosocial behaviors at two points in time during the school year. In this study, 430 3rd-5th grade children, their peers, and their teachers were surveyed. Children's consumption of media violence early in the school year predicted higher verbally aggressive behavior, higher relationally aggressive behavior, higher physically aggressive behavior, and less prosocial behavior later in the school year. Additionally, these effects were mediated by hostile attribution bias. The findings are interpreted within the theoretical framework of the General Aggression Model.     

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.     

Perceived social support,coping, and symptoms of distress in American and Spanish students

Abstract

The aim of this study was to test whether coping responses mediated the influence of perceived social support on symptoms of anxiety/depression, social withdrawal, and aggressive behavior in American (N=349) and Spanish students (N=437). Participants completed measures of perceived support, social stress, coping, and distress. Coping partially mediated relations between perceived support and distress, with coping mediation most evident in individuals facing high levels of social stress. Decreased use of disengagement coping by individuals with high perceived support appears to partially explain the protective value of perceived social support. Multiple group covariance structure analysis showed that models linking perceived support, coping, and distress were very similar across cultures, suggesting that the mechanisms underlying decreased risk for individuals with high perceived support may be relatively independent of cultural context, and that interventions designed to increase perceived support and decrease disengagement could be appropriate in both cultures.     

Justification of interpersonal aggression in Japanese,American, and Spanish students

Six hundred and thirty‐two university students of both sexes—242 Japanese (137 males and 105 females), 190 Spanish (71 males and 119 females), and 200 American (100 males and 100 females)—completed a questionnaire that examined their attitudes toward various kinds of aggression directed at other people in different situations that ranged from self‐defense to a method of overcoming communication problems. Factor analysis revealed three factors: physical aggression (killing, torture, and hitting), direct verbal aggression (shouting and rage), and indirect verbal aggression (being ironic and hindering). The basic factor structure of the Japanese, the Spanish, and the USA samples was similar. In all samples, men showed a higher justification of physical aggressive acts in any situation and of indirect verbal aggression in nondefensive circumstances. Cultural differences were found in the degree of justification of the three factors: in all kinds of situations, Japanese students showed a lower justification of indirect verbal aggression but a higher justification of direct verbal aggression than USA and Spain samples. Physical aggression in defensive situations is justified more by Americans than by Japanese and Spanish students. These findings suggest the existence of a common basic moral code about physical aggressive acts, but there seems to be a cultural influence on moral codes concerning verbal aggressive acts. Oriental cultures, with an interdependent construal of self, seem to be more permissive of direct verbal aggression compared with Western cultures, but they have less tolerance for indirect verbal aggression. There were practically no significant differences between American and Spanish scores. Aggr. Behav. 25:185–195, 1999. © 1999 Wiley‐Liss, Inc.