Intermale fighting and predatory behavior in house mice: An analysis of behavioral content

Two forms of aggression, intermale and predatory, wwere compared on the basis of behavioral content. Male wild mice were presented with opponents of two types, nonaggressive male mice and crickets, and the amounts of time spent in each of 18 behaviors were recorded. Results from analyses of variance and principal components analyses indicated that the structure of behavioral content differs greatly for intermale fighting and predatory behavior. It was, therefore, concluded that the integrated patterns of beahvior were controlled by separate mechanisms for predatory versus intermale aggression.     

Intermale aggression in rats selected for emotional reactivity and their reciprocal F1 and F2 hybrids

The aggressive behavior of two selectively bred rat strains (high “H” and low “L” emotional reactivity) and their reciprocal F1 and F2 hybrids were measured during three consecutive days in home-cage intruder tests. In terms of biting, bite latency, on-top-of and aggressive grooming, L males were more aggressive than H and F1 males. There was no difference between H and F1, nor between HLF1 and LHF1 with the exception that LHF1 showed more on-top-of. About one fourth of F2 males were equal to or more aggressive than L in terms of bite latency and number of bites. These findings suggest that aggressiveness was inherited as a recessive, monogenic trait in these rats.     

Enhanced social docility in male hooded rats by dermal cautery of the vibrissal pads

Ablation of the vibrissal pads in rats causes subsequent deposition of scar tissue with little or no regrowth of the vibrissae. Cauterized and intact mature male Long Evans rats were tested for shockelicited fighting, mouse killing, and colony intrusion forms of laboratory-induced aggression. The results revealed that only conspecific social fighting is blocked by ablation of the major vibrissal follicles. Although no significant group differences were noted in tests for mouse killing, shock-elicited paired fighting and territorial defense against a strange intruder were minimal in cauterized groups. The results emphasize the importance of specific sensory experience in reference to distinct forms of aggressive responding and support a new experimental technique for further investigation of sensory interactions with sources of aggressive behavior.     

Association between intermale aggression and genetically-defined tryptophan hydroxylase activity in the mouse brain

The relationship between the genetically defined intensity of intermale aggression and the activity of brain tryptophan hydroxylase (TPH) has been studied in inbred mice. No association between the enzyme activity and the percentage of aggressive mice (reflecting the predisposition to aggressive reaction) was revealed. However, a significant positive interstrain correlation between brain TPH activity and accumulated attacking time (reflecting fight intensity) was identified. No correlation was found between TPH activity and the accumulated attacking time in segregating F2 (BALB × C57BL) mice. In conclusion, TPH is an important, but not the only factor controlling the intensity of intermale aggression in mice. © 1996 Wiley-Liss, Inc.     

Assessing the role of aggression,empathy, and self‐serving cognitive distortions in trait emotional manipulation

This study extended the examination of the predictors of emotional manipulation. Participants (N = 243) completed measures of trait emotional manipulation, emotional intelligence, social skills, psychopathy, aggression, empathy, and self‐serving cognitive distortions in a cross‐sectional correlational design. For males, higher levels of emotional intelligence, social information processing, indirect aggression, and self‐serving cognitive distortions significantly predicted emotional manipulation. For females, being younger, higher levels of emotional intelligence, indirect aggression, primary psychopathic traits, and lower levels of social awareness significantly predicted emotional manipulation. However for females, emotional intelligence acted as a suppressor. These findings support previous indications that the mechanisms behind emotional manipulation differ as a function of gender. Future research could include ability, rather than trait measures of emotional manipulation, as well as the role of context (such as intimate relationships or workplace environments), thereby allowing additional examination of the nomological network of emotional manipulation.     

Distractor effect on the latent inhibition of conditioned flavor aversion in rats

Using a conditioned flavor aversion procedure with rats as subjects, the effect of the addition of a distractor stimulus on the magnitude of the latent inhibition effect was examined. Experiment 1 showed that latent inhibition to vinegar was attenuated by the addition of sucrose during preexposure. On the other hand, sucrose added during conditioning to vinegar did not attenuate latent inhibition. It was also found that the degree of latent inhibition to the vinegar-sucrose compound solution was less when vinegar alone was preexposed (i.e., when sucrose was added only during conditioning) than when the compound solution was preexposed (i.e., when sucrose was added both during preexposure and during conditioning). Experiment 2 gave similar results but with sucrose assigned as the target flavor and vinegar as the distractor. These findings are in full agreement with the generalization decrement account of latent inhibition.     

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.     

Attack and defensive behaviors in the albino mouse

Attack by dominant male colony mice on intruders included chasing and lateral attack behaviors, while the corresponding intruder behaviors were flight, boxing, and checking. Both of these are similar to the attack and defensive behaviors of colony rats and intruders. However, mice did not show a significant constraint on bites to ventral areas, and the rat defensive behavior of lying on the back, which is effective because of this constraint, was rare; the corresponding “on-top” behavior of attackers was almost absent in mice. These findings strongly support the view that intraspecific attack and defensive behaviors, and target sites for bites, are interrelated factors facilitating effective but nonlethal agonistic interactions in muroid rodents.     

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.     

Separate neural sites for d-amphetamine suppression of mouse killing and feeding behavior in rats

The present study was conducted to investigate several possible neural sites for d-amphetamine's effect on mouse killing and feeding behaviors. d-Amphetamine (10, 20, and 30 μg) injected into each lateral ventricle, suppressed mouse kiling, food, and water intake in a dose-dependent manner. Bilateral adminstration of d-amphetamine (20 μg) into the central amygdaloid nucleus abolished mouse killing behavior but did not affect feeding and drinking. By contrast, bilateral amphetamine injections into the substantia nigra, or into the ventral region of the caudate nucleus, did not suppress mouse killing behavior, but significantly decreased food and water intake. The lateral hypothalamus was sensitive to d-amphetamine injections, which suppressed mouse killing and food intake as well as water intake. d-Amphetamine injections into the nucleus accumbens produced inconsistent effects on mouse killing and feeding. Our observations suggest a differentiation of the neural sites that mediate feeding from those underlying mouse killing behavior.     

The effect of on‐ or off‐line extinction of a first‐order conditioned stimulus on a second‐order conditioned response in rats

In a water‐licking experiment with rats, the effects of the extinction of a first‐order conditioned stimulus (CS1) on the suppression of licking established for a second‐order conditioned stimulus (CS2) were explored. Extinction of the first‐order conditioned response (CR1) attenuated the conditioned suppression induced by CS2 when the rats had been allowed to lick water during the CR1 extinction phase. However, if water had been unavailable during the CR1 extinction phase, suppression by CS2 was not affected. The latter result is consistent with other studies of rats' conditioned suppression and suggests that the underlying mechanism of second‐order conditioning in this experiment is a connection between CS2 and the response elicited by CS1 rather than a CS2‐CS1 connection. The former result was interpreted as the CR1 extinction phase encouraging the rats to lick water despite the fear elicited by CS1, and thus, in testing, they licked despite the fear elicited by CS2.     

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.     

Play fighting and the development of agonistic behavior in male and female rats

Two longitudinal studies were conducted to quantify the social behaviors exhibited by both male and female Long-Evans rats from the immediate postweaning period until young adulthood. In Experiment 1, male sibling pairs engaged in a high level of play fighting during the early juvenile period but such activity declined to a level significantly lower than that of female and mixed-sex pairs after 54 days of age. In Experiment 2, social exchanges during maturation were examined during the presence and absence of the piloerection response in an effort to distinguish play fighting from agonistic interactions. In male pairs, piloerection was rarely seen before 55–75 days of age but thereafter occurred with increasing frequency especially among dominant males. Furthermore, subordinate males retreated from their dominant partners and remained in an escape chamber for a significant amount of time only during encounters involving the exhibition of piloerection. This finding suggests that piloerection can be useful in identifying play and aggressive interactions. In female and heterosexual pairs, piloerection was observed infrequently during social encounters occurring throughout maturation. In addition, when given the opportunity to escape, females were less likely to retreat from play activity if their partner was another female than a male.     

Dominance and age-related changes in the play fighting of intact and post-weaning castrated male rats (Rattus norvegicus)

The play fighting behaviour of male rats (Rattus norvegicus) castrated at weaning was compared to that of intact controls during the juvenile and post-pubertal phases of development. Following puberty, both the castrated and intact animals exhibited an age-related change in their play fighting; the frequency of initiating play fighting decreased and juvenile patterns of playful defense were replaced by more adult-like patterns. As these changes occurred even in the absence of the pubertal surge of gonadal hormones, they were more likely to result from the organizational effects of gonadal hormones in the perinatal period than the activational effects of these hormones at puberty. Although the castrated animals exhibited the age-related changes in behaviour, they did not exhibit the asymmetries in play associated with dominance relationships. As demonstrated in previous studies, in pairs of intact rats, the animal that attacks the most and uses more juvenile defenses during play fighting and weighs the least is typically the subordinate. In the castrates, asymmetries in weight and playful defense are not related to play frequency, indicating the absence of a dominance relationship. Although the characteristic changes in male play fighting at puberty are independent of the activational effects of gonadal hormones, dominance relationships and their associated changes in play fighting are dependent on these hormones. Therefore, in the perinatal period gonadal hormones most likely organize the age-related changes in play behaviour, whereas post-pubertally gonadal hormones activate dominance relationships and thus, indirectly modify play fighting by affecting dominance-associated assymetries in behaviour. © 1996 Wiley-Liss, Inc.     

Relationships between testosterone metabolism in the brain,other endocrine variables and intermale aggression in mice

Relationships between some endocrine variables (plasma testosterone and estradiol; in vitro gonadal biosynthesis from pregnenolone precursor and adrenocortical biosynthesis from progesterone precursor; in vitro activity of 17β-hydroxysteroid de-hydrogenase (17β-HSDH) and of aromatizing enzymes in the subcellular fractions of the brain) and isolation-induced inter-male aggressiveness were studied. A significant positive correlation was found between fighting behavior, measured by the number of wins in a series of paired encounters, and the activity of brain 17β-HSDH. A significant inverse correlation was found between fighting behavior and the activity of aromatizing enzymes in the nuclear fraction of the brain. No significant correlations were found between fighting and the other endocrine variables investigated. These results may suggest that the conversions testosterone → androstenedione and testosterone → estradiol in the brain play a role in the control of inter-male fighting in the mouse. These results may also account for the effect of repeated wins and defeats on brain steroidogenesis.     

Discrete-trial training for autistic children when reward is delayed: a comparison of conditioned cue value and response marking

Three children with autism were taught to identify pictures of objects. Their speed of acquisition of receptive speech skills was compared across two conditions. In the cue-value condition, a compound audiovisual stimulus was presented after correct responses and again when a primary reinforcer was delivered after a 5-s delay; in the response-marking condition, a second stimulus was presented after both correct and incorrect responses, but not prior to the primary reinforcer. In both conditions primary reinforcement was delayed for 5 s. Although the children learned receptive speech skills in both conditions, acquisition was faster in the cue-value condition.     

Contradictory asymmetries in body and weapon size,and assessment in fighting male prawns,Macrobrachium rosenbergii

Asymmetries in weapon size and body size, both contributing to an animal's fighting ability, may be contradictory in two fighting Macrobrachium rosenbergii males: One male may be larger in body size but smaller in cheliped size than its rival. The aim of the study was to determine the relevance of these two asymmetries in the assessment of relative fighting ability, and to reveal the effect of the asymmetry level on the structure of contests. Thirty contests were staged between male prawns from the ‘blue-clawed’ morphotype and the ‘orange-clawed’ morphotype. The blue-clawed males were 0%, 10%, or 20% larger in cheliped length but 93%, 45%, or 25% smaller in weight, respectively (n = 10), as compared to their orange-clawed opponents. The blue-clawed males with 10% and 20% advantage in cheliped length almost invariably won the contests. When similar in cheliped length, the 93% smaller blue-clawed males still won half of the contests. This indicated that the prawns ignored large asymmetries in body size even when no asymmetry in cheliped size existed. The results suggest that only cheliped size is used by M. rosenbergii males in the assessment of fighting ability. The effect of asymmetry level on contest structure was apparent only with the increase from 10% to 20% difference in cheliped size: Both the frequency and the intensity of fighting were lower in contests between prawns with 20% difference, as compared to 0% and 10% difference in cheliped length. Aggr. Behav. 23:81–91, 1997.© 1997 Wiley-Liss, Inc.     

Initial excitatory conditioning with the truly random control procedure in rats: The effects of density of the conditioned stimulus

The present experiments were designed to test whether initial excitatory conditioning to a stimulus was obtained, using a within-subject design of the truly random control (TRC) procedure, and to examine the effects of the density of the conditioned stimulus on it. In Experiment 1, the effect of the three levels of CS density (50%, 25%, 20%) was assessed at six different stages of training, using the conditioned suppression of licking in rats. Although all of the groups given the TRC procedure showed evidence of initial excitatory conditioning, it was more marked in the group with the highest CS density than in the other groups. Experiment 2 confirmed the results of Experiment 1, using a between-subject design. The findings are in line with predictions from the Rescorla-Wagner model, and are discussed with reference to other contemporary theories of associative learning.