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.     

Resolution of dilemmas: A mathematical theory

A mathematical formulation for a dilemma (i.e. a situation in which a very difficult choice between two alternatives must be made) is given. Multiple-objective programming is assumed as the model for a single decision maker. It is shown that, in principle, any dilemma is resolvable. Furthermore, there is always more than one way in which to resolve a dilemma. Illustrative examples from non-convex optimization are presented.     

Social isolation,aggression, and dominance in attacks in juvenile angelfish,Pterophyllum scalare

The effects of social isolation on aggressive behavior and rank order have been investigated in small groups of juvenile angelfish, Pterophyllum scalare. An experimental protocol including a “double transfer” of the subjects was used, in which fish were transferred to new aquaria in groups, before subsequent isolation and regrouping. A significant decrease in aggression was observed in the first recording session following both isolation and group transfer, after which the level returned to that recorded in the home tanks. The social hierarchy was also perturbed, but changes generally involed the two highest ranking fish in two out of the three groups, and were found not to be statistically significant. The behavior patterns are interpreted as adaptive responses to environmental change. © 1993 Wiley-Liss, Inc.     

Maternal views on aggression: Japan and Israel

Maternal views on aggressive behavior in their children were investigated in Japan and Israel. Sixty Japanese and 60 Israeli mothers of kindergarten children were interviewed individually about their children's fighting and quarreling. The findings indicate that both Japanese and Israeli mothers disapprove of their children's aggression on the basis of their value system, but their views of the same aggressive behavior differ considerably; Japanese mothers consider aggression among children as natural; aggression is a fact of life which has its constructive as well as destructive aspects, but it should be kept under control in order not to cause harm to others. Israeli mothers consider their children's aggression to be dangerous both for the child and for the relationship with the opponent. It is approved as a reaction to assault, mainly in self-defense and considered caused by emotions, tension, and lack of self-control. Thus, aggression is perceived by Japanese mothers as a natural and necessary aspect of development, while Israeli mothers perceive the same behaviors as justified mainly as reactions to assault or provocation and as expressing negative emotional states. © 1992 Wiley-Liss, Inc.     

A sensory contact model for the study of aggressive and submissive behavior in male mice

The technique for simultaneous development of aggressive and submissive behaviors as a result of successive experiences of defeats or victories in daily intermale confrontations in male mice permanently living under sensory contact conditions is offered for behavioral, pharmacological, and neurophysiological studies of mechanisms of agonistic social relations. Distant sensory contact is achieved by placing a pair of males into a common cage separated by a transparent partition with holes permitting visual contact and the individuals perceiving each other's odors but preventing any physical at contact all times except for 10-min daily tests. These conditions essentially elicit aggression in winner males and quickly result in submission by losers of the same strain of mice. The meaning of consecutive stages of the technique, the problem of controls, and applications of this model are discussed.     

Effects of ritanserin on offense and defense in male mice

Effects of ritanserin on agonistic behavior of isolated mice exhibiting aggressive or nonaggressive behavioral strategies were studied in pair-wise encounters with group-housed opponents. An ethological approach to behavioral scoring is adopted, which allows for examination of the profiles of individual subjects. Although the data generally support the view that ritanser in has little effect on offense or defense in male mice, the stimulation of pre-aggressive behavior (threats, alerts, tail rattles) was detected in some nonaggressive mice. © 1995 Wiley-Liss, Inc.     

Exposure to ozone inhibits isolation-induced aggressive behavior of adult CD-1 male mice

Continuous exposure to ozone (O₃, 1.2 ppm) in adult CD-1 male mice for 20 consecutive days markedly influenced a number of items of aggressive behavior induced by 59 days of individual housing. The behavior of mice was videotaped on days 1, 3, and 5 of five consecutive daily encounters (10 min each; isolation days 55, 57, and 59). Ozone exposure caused an abatement of aggressive behavior and enhanced fear-associated displays shown by a significant decrease in the frequency of attacking and digging and an increase in freezing. Moreover, O₃ induced a decrease of time spent in attacking and exploration/activity. Nonexposed animals exhibited a day-dependent increase in self-grooming frequency which was not observed in O₃ mice; by contrast, freezing was higher in O₃ mice on day 5 of the test. Data suggest that O₃ exposure produces a remarkable reduction of mouse aggression, indirectly confirming previous findings on physical and neurobehavioral effects of O₃. © 1995 Wiley-Liss, Inc.     

Effects of neonatal treatment with 1-(2,5-dimethoxy-4-lodophenyl)-2 aminopropane HCI (DOI) and ritanserin on agonistic behavior in adult male and female rats

The role played by the neonatal 5-hydroxytryptamine (5HT) system in the organization and sexual differentiation of adult agonistic behavior was investigated in rats. Focus was on the 5HT2 receptor subtype, which has been demonstrated to be involved in agonism control in the adult. 5HT2 activity was experimentally manipulated by administration of a specific agonist [1-(2, 5-dimethoxy-4-iodophenyl)-2-aminopropane HCl (DOI)] or antagonist (ritanserin) during the second week of life, when serotonin is known to concur to anatomical and behavioral sexual differentiation. Interactions between early 5HT2 activity, genetic sex, and neonatal circulating testosterone (T) were studied by administering the ligands to males, females, and androgenized females. At adulthood, the animals were tested for both aspects of agonism, i. e., aggression and defense, in a 20-min confrontation with an unfamiliar conspecific of the same sex, age, body weight, and social experience. Neonatal administration of the 5HT2 antagonist ritanserin increased aggression independently of sex; it also increased defense, but this effect was confined to males. The agonist DOI had no effect on aggression, but enhanced defense in males and androgenized females, with an effect which depended therefore more on neonatal T than genetic sex. Females appeared in general less sensitive to neonatal 5HT2 manipulation than both androgenized females and males; this suggests that neonatal T is crucial for experimental modifications of neonatal 5HT2 activity to have any consistent effect on adult agonistic behavior. On the other hand, effects observed in males and androgenized females were dependent on the behavior considered and the drug administered. This was especially evident for defense, enhanced by ritanserin in males only, and in both males and androgenized females by DOI. Neonatal 5HT2 activity seems therefore to play a role in the modulation of adult agonistic behaviors, which depends on the behavior considered and is under multiple control of genetic sex and hormonal neonatal substrate. © 1994 Wiley-Liss, Inc.     

Influence of timing of post-weaning isolation on play fighting and serious aggression in the male golden hamster (Mesocricetus auratus)

Effects of timing of social isolation on play fighting and serious fighting were studied at different ages in male golden hamsters. Litters were isolated at 21, 35, and 65 days of age, and tested in a resident-intruder paradigm. Behaviors were compared within grous and with a fourth group of socially reared conspecifics. The earlier the pups were isolated, the more they engaged in play activities. Later, in adulthood, the aggression level of the same animals was retested using the same paradigm. The three isolated groups showed a high level of aggression, with significant differences among them. When compared with socially reared subjects, a reliable difference in the level of aggression was also found. These results support the view that early social experience is important, suggesting that isolation during early critical periods of socialization has a significant impact on play fighting, whereas short periods of isolation may be enough to trigger adult agonistic behavior. © 1994 Wiley-Liss, Inc.     

Defensive reactions of “wild-type” and “Domesticated” wild rats to approach and contact by a threat stimulus

Selective breeding of wild rats over many generations on the basis of low or high defensive threat and attack to human approach and contact has produced highly polarized “domesticated” and “wild-type” animals. Because the selection procedure selectively involves these two defense patterns, and these clearly differ in the two groups, it is of interest to determine if other, nonselected, defensive behaviors to threat stimuli also change. “Domesticated” and “wild-type” rats of the thirty-fifth generation were run in a fear defense test battery (F/DTB) to systematically evaluate defensive behaviors to a variety of present threat stimuli. “Domesticated” rats showed reduced avoidance and slower flight speed to an approaching experimenter, reduced jump/startle response to handelap and dorsal contact, less vocalization and boxing to vibrissae stimulation or to an anesthetized conspecific, and reduced defensiveness to an attempted pickup by the experimenter. These results indicate that selective bi-directional breeding for defensive threat and attack to human approach and contact produces group differences in a variety of defensive behaviors, and in defensiveness to stimuli other than those on which the selection was based. © 1994 Wiley-Liss, Inc.