Effect of conspecific sex on aggression during pregnancy and lactation in golden hamsters

The effect of conspecific sex on maternal aggression in hamsters was determined by comparing the frequency of aggressive responses by dams continuously housed with either a virgin male or female cagemate during pregnancy and lactation. Dams easily established aggressive dominance over male cagemates soon after pairing, and their aggression was low thereafter for the duration of pregnancy and lactation. The aggression of dams with females, on the other hand, tended to fluctuate with highs during mid pregnancy and mid lactation and lows around birth. When dam aggression was low around birth, female cagemates frequently became aggressively dominant, and several dams lost their litters. The higher aggression of dams toward females than males is probably a reflection of greater intrasexual competition for environmental resources that includes pups.     

Variation in aggressive behavior and anatomo-physiological correlates generated by crowding without physical contact in the house mouse

Behavioral, physiological (i.e., endocrine), and anatomical consequences of crowding in mice were studied in a situation where animals were in auditory, visual, olfactory, and tactile contact but restrained from full physical interactions, to prevent overt aggression. Males that cohabited with females undisturbed by neighboring conspecifics showed greater propensity to attack same-sex intruders and had higher plasma testosterone levels than did their “crowded” counterparts, that is, males cohabiting with females and housed adjacent to other male/female pairs. In this respect, the latter animals resembled submissive males. However, a significant increase in weight of androgen-dependent target organs (i.e., seminal vesicles and preputial glands) was found in crowded males. These data indicate that despite the observed inhibition of social aggression these males are not physiologically comparable (homologous) to male mice that experienced defeat and the stress of submission during fighting. The intriguing possibility that different conversion pathway of testosterone are accelerated, as a result of social communication, in males living in these two environments and the behavioral implications of these possibilities are discussed. Finally, the parental behavior of crowded animals, although not freely interacting with each other, was disrupted, causing a marked decrease in reproductive success. In this situation a high incidence of infanticide of their offspring by both parents was observed, whereas this behavior was virtually absent in non-crowded male/female pairs.     

Perceiving while acting: action affects perception

In two experiments we studied how motor responses affect stimulus encoding when stimuli and responses are functionally unrelated and merely overlap in time. Such R-S effects across S-R assignments have been reported by Schubö, Aschersleben, and Prinz (2001), who found that stimulus encoding was affected by concurrent response execution in the sense of a contrast (i.e., emphasizing differences). The present study aimed at elucidating the mechanisms underlying this effect. Experiment 1 studied the time course of the R-S effect. Contrast was only obtained for short intertrial intervals (ITIs). With long ITIs contrast turned into assimilation (i.e., emphasizing similarities). Experiment 2 excluded an interpretation of the assimilation effect in terms of motor repetition. Our findings support the notion of a shared representational domain for perception and action control, and suggest that contrast between stimulus and response codes emerges when two S-R assignments compete with each other in perception. When perceptual competition is over, assimilation emerges in memory.     

A Framework for Explaining Aggression Involving Groups

Aggression involving groups (versus individuals) can be particularly severe (e.g., hazings). Although an impressive amount of experimental research on the aggression of individuals exists, relatively less experimental research on aggression involving groups exists. We use existing theories of aggression and the available research to present a framework of aggression when groups are involved. We propose a provisional model that suggests that the extent of aggression to be committed depends on the composition of both source (i.e., perpetrators – group or individual) and target (i.e., victims – group or individual) entities. Evidence suggests that groups commit and receive more aggression than individuals. We propose that accessible hostile thoughts and the experience of negative affect contribute to the target effect (i.e., more aggression committed toward groups versus individuals), whereas disinhibition processes and arousal contribute to the source effect (i.e., more aggression committed by groups versus individuals). Our framework can guide future theory and research on aggression involving groups.     

Nursing behavior of infant pigtail monkeys (Macaca nemestrina): preferences for nipples.

Nursing behavior of 56 singleton infant pigtail monkeys (Macaca nemestrina) was monitored. Infants over 1 mo. of age showed strong preferences for one of their mothers' nipples, while few infants less than 1 mo. old did so. The infants which had the lowest birthweights for each sex showed no clear preference even though they were older than 1 mo. A trend toward lateral preference (for the right nipple) was identical for male and female infants. Analysis of the development of preference for nipple may provide useful information of assessing development progress.     

Does fear modulate defensive and offensive types of maternal attack in mice?

Swiss CD‐1 lactating mice show a different pattern of attack toward intruders of differing sex, displaying defensive attack against the male (bites on the head and ventrum associated with fear) and offensive attack against the female (bites on the back and flanks with no elicitation of fear). This dichotomy may reflect diverse functions of maternal aggression: the attack toward males (the more infanticidal gender in laboratory strains) has been interpreted as a counterstrategy to infanticide, whereas the attack toward females may serve to establish a social hierarchy or to space rivals of the same sex. In terms of proximal mechanisms, fear may be a key factor involved in the modulation of the different patterns of attack. In Experiment 1 we compared the pattern of attack of lactating females in Swiss CD‐1 and Wild mice toward male and female intruders in relation to fear components of behavior of the attacking dams. Results showed that in Swiss mice, male intruders were attacked with a defensive type of attack accompanied by high levels of fear, whereas female intruders did not elicit fear in the attacking animal but were attacked with an offensive pattern. In Wild mice, both types of intruders were attacked with a defensive pattern; notwithstanding, fear was evident only toward male intruders. This suggests that fear is not totally responsible for the expression of the defensive type of attack. To test the hypothesis that defensive attack toward male and female intruders may be related to the infanticidal potential of the intruder, Experiment 2 examined levels of infanticide in both male and female Swiss CD‐1 and Wild mice. Swiss female mice showed virtually no infanticidal behavior, whereas Swiss males and both sexes of Wild mice showed similarly high levels of infanticide (55%–75%). From a game theory perspective, the defensive pattern of maternal attack toward female intruders in Wild mice is discussed as “extreme” defense of a high value resource and thus, functionally, a competitive form of aggression. Aggr. Behav. 26:193–203, 2000. © 2000 Wiley‐Liss, Inc.     

Maternal aggression in rats: Changes over pregnancy and lactation in a sprague-dawley strain

Maternal aggression in a Sprague-Dawley strain of laboratory rat (Charles River CD) was explored from Day 1 after mating on Day 0 through Day 24 of lactation (L0-L24). Aggression toward unfamiliar male “intruders” during 10-min tests was low among nonpregnant, nonlactating females and during the first 10 days of gestation. Frequency of attack on intruders increased moderately but significantly by Gestation Day 16 (G16; Experiment 1) or G21 (Experiment 2), a prepartum phenomenon not previously reported in laboratory rats. Levels of aggression were highest, however, during the first 9 days of lactation, when attacks averaged more than 6 per 10-min session. Attacks declined sharply in frequency after L14 and by L24 did not exceed levels observed among nonpregnant females. Experiment 3 examined the importance of the test site (home cage with nest and pups, if any, vs unfamiliar cage without nest or pups) to agonistic behavior associated with pregnancy and lactation. Late pregnant females tested in a novel cage were not aggressive; however, females tested shortly after delivering their pups were highly aggressive, averaging over four attacks per 5-min session. In novel cage tests frequency of attack remained high through L4 but declined significantly by L7. These data are consistent with the hypothesis that maternal aggression at its onset is primarily under hormonal control, but becomes increasingly dependent upon external factors, presumably pup stimulation, during the postpartum period.     

Effects of serotonergic and cholinergic antagonists on suckling behavior of neonatal, infant, and weanling rat pups

In Experiment 1, Sprague-Dawley rat pups at postnatal days 3-4, 7-8, 10-11, 15-16, and 23-24 were tested for suckling behavior on their anesthesized multiparous dams following administration of metergoline or scopolamine. The serotonergic antagonist, metergoline, inhibited suckling in 3- to 4- and 7- to 8-day-old rat pups, but was not found to influence suckling in older pups. Scopolamine, a cholinergic antagonist, reduced suckling primarily in 3- to 4-day-old pups. In Experiment 2, parity of the maternal female was manipulated to assess whether this variable would influence suckling behavior and the effects of metergoline on suckling of weanlings. Baseline levels of suckling were reduced in 23- to 24-day-old pups of primiparous dams when compared with multiparous-derived offspring. Administration of metergoline increased the amount of time that these primiparous-derived pups spent attached to nipples, but did not influence suckling of offspring of multiparous dams, perhaps as a result of a ceiling effect on suckling behavior in these animals.     

The displaced aggression questionnaire

Previous measures of aggressive personality have focused on direct aggression (i.e., retaliation toward the provoking agent). An original self-report measure of trait displaced aggression is presented. Exploratory and confirmatory factor analyses provided support for a 3-factor conceptualization of the construct. These analyses identified an affective dimension (angry rumination), a cognitive dimension (revenge planning), and a behavioral dimension (general tendency to engage in displaced aggression). The trait measure demonstrated good internal consistency and test-retest reliability as well as convergent and discriminant construct validity. Unlike other related personality measures, trait displaced aggression significantly predicted indirect indicators of real-world displaced aggression (i.e., self-reported domestic abuse and road rage) as well as laboratory displaced aggression in 2 experiments.     

Hemispheric differences in object identification

Although the right hemisphere is thought to be preferentially involved in visuospatial processing, the specialization of the two hemispheres with respect to object identification is unclear. The present study investigated the effects of hemifield presentation on object and word identification by presenting objects (Experiment 1) and words (Experiment 2) in a rapid visual stream of distracters. In Experiment 1, object images presented in the left visual field (i.e., to the right hemisphere) were identified with shorter display times. In addition, the left visual field advantage was greater for inverted objects. In Experiment 2, words presented in the right visual field (i.e., to the left hemisphere) under similar conditions were identified with shorter display times. These results support the idea that the right hemisphere is specialized with regard to object identification.     

On the orienting value of attitudes: attitude accessibility as a determinant of an object's attraction of visual attention.

Four experiments tested the hypothesis that objects toward which individuals hold attitudes that are highly accessible from memory (i.e., attitude-evoking objects) are more likely to attract attention when presented in a visual display than objects involving less accessible attitudes. In Experiments 1 and 2, Ss were more likely to notice and report such attitude-evoking objects. Experiment 3 yielded evidence of incidental attention; Ss noticed attitude-evoking objects even when the task made it beneficial to ignore the objects. Experiment 4 demonstrated that inclusion of attitude-evoking objects as distractor items interfered with Ss' performance of a visual search task. Apparently, attitude-evoking stimuli attract attention automatically. Thus, accessible attitudes provide the functional benefit of orienting an individual's visual attention toward objects with potential hedonic consequences.     

The relative importance of psychopathy-related traits in predicting impersonal sex and hostile masculinity

This paper reports the relative contributions of several facets of subclinical psychopathy (i.e., callous affect, erratic lifestyle, interpersonal manipulation), subclinical narcissism (i.e., entitlement, exploitation), and trait aggression (i.e., anger) to the prediction of four enduring attitudes towards women and sexual assault (i.e., hostility towards women, negative attitudes regarding women, sexual dominance, impersonal sex) and a behavioral indicator of an impersonal sexual behavior (i.e., number of one-night stands). Survey data were collected from 470 single men living in the Detroit Metropolitan area. The importance of personality traits varied as a function of the outcome with anger most predictive of hostility toward women; erratic lifestyle most predictive of impersonal sexual attitudes and behavior, and entitlement most predictive of sexual dominance and negative attitudes toward women. These outcome-specific findings are interpreted and directions for future research are discussed.     

Relationship between maternal aggression and maternal care in the rat

Aggression among female rats is almost entirely confined to the period of late pregnancy and lactation. Behaviorally it is similar to the aggression of males including piloerection and lateral attacks, but it differs in its function. Unlike male aggression which serves to establish a social hierarchy and a territory, i. e., is competitive, maternal aggression is protective, i. e., it serves to prevent predation of the mother's offspring. In this respect it is closely related temporally and causally to maternal care; if the offspring are removed maternal aggression wanes almost immediately–its function no longer exists! Studies on aggression by mothers, among rats, from the author's laboratory are reviewed and comparisons made with maternal care. As noted, maternal aggression and maternal care are closely related during the cycle of maternal behavior and they share a similar hormonal basis and possibly the effect of uterine stimulation, but maternal care requires prolactin and the decline of progesterone while maternal aggression appears independent of pituitary hormones and does not require a decline in progesterone. Maternal aggression like maternal care appears to be organized into a hormonal phase, during pregnancy, parturition, and for about a week postpartum and a nonhormonal phase thereafter. Bilateral radiofrequency lesions of the lateral midbrain peripeduncular nucleus (PPN) produce deficits in maternal aggression if made on lactation day 7 (L7), but not earlier, without producing significant deficits in maternal behavior. Experiments showed that the PPN does not mediate hormonally stimulated maternal aggression; it appears to mediate only nonhormonally stimulated maternal aggression. Studies on the role of pregnancy hormones on long-term retention of maternal aggression and the role of olfaction in maternal aggression are also reviewed. © 1994 Wiley-Liss, Inc.     

Infant Parasympathetic and Sympathetic Activity during Baseline,Stress and Recovery: Interactions with Prenatal Adversity Predict Physical Aggression in Toddlerhood

Exposure to prenatal adversity is associated with aggression later in life. Individual differences in autonomic nervous system (ANS) functioning, specifically nonreciprocal activation of the parasympathetic (PNS) and sympathetic (SNS) nervous systems, increase susceptibility to aggression, especially in the context of adversity. Previous work examining interactions between early adversity and ANS functioning in infancy is scarce and has not examined interaction between PNS and SNS. This study examined whether the PNS and SNS moderate the relation between cumulative prenatal risk and early physical aggression in 124 children (57% male). Cumulative risk (e.g., maternal psychiatric disorder, substance (ab)use, and social adversity) was assessed during pregnancy. Parasympathetic respiratory sinus arrhythmia (RSA) and sympathetic pre-ejection period (PEP) at baseline, in response to and during recovery from emotional challenge were measured at 6 months. Physical aggression and non-physical aggression/oppositional behavior were measured at 30 months. The results showed that cumulative prenatal risk predicted elevated physical aggression and non-physical aggression/oppositional behavior in toddlerhood; however, the effects on physical aggression were moderated by PNS and SNS functioning. Specifically, the effects of cumulative risk on physical aggression were particularly evident in children characterized by low baseline PNS activity and/or by nonreciprocal activity of the PNS and SNS, characterized by decreased activity (i.e., coinhibition) or increased activity (i.e., coactivation) of both systems at baseline and/or in response to emotional challenge. These findings extend our understanding of the interaction between perinatal risk and infant ANS functioning on developmental outcome.     

Paying for sanctions in social dilemmas: The effects of endowment asymmetry and accountability

The present research examines whether or not endowment asymmetry leads those with many endowments to contribute more than those with few endowments towards the public good (i.e., a first-order dilemma), but also towards the implementation of a sanctioning system (i.e., a second-order dilemma). In Experiment 1, we found that those with many endowments contributed more than those with few endowments in a public good dilemma without a sanctioning system present, whereas those with many endowments did not contribute more than those with few endowments toward the implementation of a sanctioning system. The latter effect, however, was eliminated when participants were accountable (i.e., when expectations that they would have to justify their decisions to others in the group were high). Experiment 2 showed that when participants were accountable, the contributions of those with many endowments (and not those with few endowments) toward the sanctioning system increased, but only when they perceived the group to be more self-evaluative in terms of morality (i.e., high-evaluation expectancy). Experiment 3 showed that this effect of evaluation expectancy only emerged when participants were accountable to the whole group rather than to only one group member.     

The recovery of identity and relative position from visual input: Further evidence for the independence of processing of what and where

Four experiments examined the manner in which item identity and relative position are recovered from visual input. A successivesame/different matching paradigm was designed in which each trial contained a prime and a target display. Each display contained a reference object (i.e., a “+”) and a located object (i.e., a letter, which fell to either the right or the left of the “+”). In Experiment 1, subjects carried out identity judgments on the letters. Experiment 2 examined relative position judgments; in Experiment 3, subjects had to judge both item identity and relative position information. Overall, these initial data suggested that identity and positional information are recovered via independent mechanisms and that these operate concurrently. This suggestion was supported by the results of Experiment 4, which in turn disconfirmed an alternative response account of performance.     

"Isn't it fun to get the respect that we're going to deserve?" Narcissism, social rejection, and aggression

Across four studies, narcissists were more angry and aggressive after experiencing a social rejection than were nonnarcissists. In Study 1, narcissism was positively correlated with feelings of anger and negatively correlated with more internalized negative emotions in a self-reported, past episode of social rejection. Study 2 replicated this effect for a concurrent lab manipulation of social rejection. In Study 3, narcissists aggressed more against someone who rejected them (i.e., direct aggression). In Study 4, narcissists were also more aggressive toward an innocent third party after experiencing social rejection (i.e., displaced aggression). Narcissists were not more aggressive after social acceptance. Self-esteem plays little role in predicting aggression in response to rejection. These results suggest that the combination of narcissism and social rejection is a powerful predictor of aggressive behavior.     

The Relationship between Anger Rumination and Aggression in Typically Developing Children and High-Risk Adolescents

This paper examines anger rumination as a risk factor of aggression in typically developing children and high-risk adolescents. Study 1 developed and evaluated the psychometric properties of a self-report measure of children’s anger rumination (Children’s Anger Rumination Scale; CARS) and its association with teacher- and peer-rated overt and relational aggression in school-aged children (n = 254, M age = 10.62). Findings offered support for the reliability and validity of the CARS as well as support for the hypothesis that children who ruminate to anger exhibit elevated levels of overt and relational aggression. Study 2 examined concurrent and prospective relationships between anger rumination and aggression and the moderating effects of trait anger in a sample of male juvenile offenders (n = 119, M age = 16.74). Latent growth curve analyses revealed that the interaction between trait anger and anger rumination predicted initial levels of aggression (i.e., intercept) and changes in aggression over time (i.e., slope). Juvenile offenders who were high in trait anger and ruminated in response to anger exhibited the highest initial levels of aggression. Contrary to our hypothesis, this group did not exhibit greater increases in aggression over time relative to others, but instead they had stably high levels of aggression at each time point. These findings suggest that cognitive-behavioral treatment strategies for aggression may be improved by educating youths about the contributory role of anger rumination in the development of aggression and providing them with adaptive alternatives to coping with feelings of anger.     

Preference for unreliable reinforcement in children with mental retardation: the role of conditioned reinforcement

We examined the effects of conditioned reinforcement on children's choice between reliable (100%) and unreliable (50%) reinforcement under various stimulus conditions in a concurrent-chains procedure. The study was conducted across three experiments. Experiments 1 and 2 were conducted under conditions similar to basic laboratory work and consisted of participants selecting from one of two black boxes (placed on a table) that were correlated with different reinforcement schedules. In Experiment 3, we assessed a participant's preference for unreliable reinforcement during conditions in which the target responses were aggression and mands. Results of the three experiments showed that the participants preferred unreliable reinforcement under certain conditions. Findings are discussed regarding the role of specific stimuli (i.e., items correlated with a reinforcement schedule, adult reactions) as conditioned reinforcers and how they may influence children's preference for a response (e.g., aggression, self-injury) that produces reinforcement on a leaner schedule than a socially desirable response (e.g., mands).     

Differential sucking by neonates of depressed versus non-depressed mothers

Forty-two neonates (M = 39-h old) of depressed and non-depressed mothers sucked on cold (50 °F) and warm (78 °F) nipples on alternating trials. Half the infants received the cold nipple on the first of the eight trials (20 s each) and the other half received the warm nipple first. Neonates of depressed mothers sucked twice as much as neonates of non-depressed mothers, suggesting arousal dysregulation, overactivity or greater hedonic behavior in the newborns of depressed mothers. Although the newborns did not show a preference for cold or warm nipples, a temperature order effect revealed that neonates who received the cold nipple on the first trial sucked significantly more on trials 2–8 than those who received the warm nipple on the first trial, suggesting that an initially cold nipple might elicit greater sucking. More research is needed on maternal mood effects and temperature of objects to determine how these factors affect neonatal sucking behaviors.