Neonatal testosterone augmentation increases juvenile play fighting but does not influence the adult dominance relationships of male rats

Neonatal male rats were either injected subcutaneously with testosterone propionate (TP) or oil vehicle. When weaned, each treated pup was paired with an untreated male sibling. The play fighting of TP-and oil-treated rats were compared at the juvenile phase (30–36 days), and in adulthood (84–90 days). In the juvenile phase, the rate of initiating playful attacks was significantly greater for TP-treated rats. Playful defense in response to such attacks did not differ between TP- and oil-treated rats. At the completion of the study, cortical thickness was measured for all the groups of rats. Oil treatment decreased overall cortical thickness relative to untreated pairmates, whereas TP treatment did not. Both oil and TP treatment abolished the asymmetry in hemispheric thickness, which was present in the untreated pairmates. The reversal of at least one of these injectioninduced changes in the cortex by TP provided independent evidence for the effectiveness of the TP treatment. As adults, neither the TP treatment nor the oil treatment influenced which pairmate became dominant. Dominance was judged by which pairmate initiated less playful attacks. Therefore, it is concluded that the early neonatal testosterone surge is not likely to be a factor in influencing the behaviors that lead to adult dominance. In contrast, play fighting is influenced by hormonal events in this early neonatal phase. It thus appears that play fighting and the aggressive systems subserving dominance relationships are differentially controlled. © 1992 Wiley-Liss, Inc.     

Playful defensive responses in adult male rats depend on the status of the unfamiliar opponent

Adult male rats reared as pairmates from weaning were tested in a neutral arena with both members of another pair (one at a time). The unfamiliar pairs were found to engage in play fighting, although they were more likely to escalate the encounter into serious fighting than were pairs of familiar rats. Based on their within‐home pair behavior, each pairmate was designated as a dominant or a subordinate. When the test encounters between unfamiliar males were analyzed with regard to whether the pairings consisted of two dominants, two subordinates, or a mixed pair, the pattern of play fighting was found to be attenuated. Both dominants and subordinates were more likely to initiate playful encounters, to respond defensively during these encounters, and to do so using adult‐typical tactics of defense when paired with an unfamiliar rat that was dominant in its home cage. The mechanisms by which the home status of unfamiliar male rats can be identified by another male are discussed, particularly with regard to the role that play fighting may serve for this function. It is concluded that the data support the hypothesis that play fighting can be used by adult rats for social testing, which in this case seems to involve ascertaining the opponent's fighting capability. Aggr. Behav. 25:141–152, 1999. © 1999 Wiley‐Liss, Inc.     

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.     

A multivariate analysis of social dominance in children

The social dominance behavior of dyads of unacquainted, same-sex 31/2 year-olds was observed in a familiar laboratory playroom under two conditions: A free play situation and a situation where candy was introduced. In each of the two conditions, a principal components analysis was used to explore two issues: the usefulness of the multivariate approach in devising a definition of dominance, and the cross-situational stability of the construct. In the free play session, the first principal component that emerged was consistent with a theoretical definition of dominance. This picture was disrupted by the introduction of candy in the second condition. However, a high correlation was found between the dominance hierarchies established in each situation. It was concluded that the multivariate analysis is a useful method for the study of dominance. The generalizability of social dominance across settings was discussed as a possible explanation for the high cross-situational stability.     

Influence of dominance on the development of play fighting in pairs of male Syrian golden hamsters (Mesocricetus auratus)

In the highly social rat, male juvenile and adult subordinates initiate more playful contacts with dominant pairmates than vice versa. This study examined the effect of dominance on playful contacts in the relatively asocial golden hamster. Pairs of male hamsters were reared together from weaning, and their play was filmed in the juvenile (28-36 days) and the young adult (60-70 days) stages of development. By the adult stage, it became clear that one pairmate was dominant over the other. The dominant pairmate launched all aggressive attacks (i. e., bites to the lower flanks and rump), and the subordinate pairmate performed all the submissive gesturing (e. g., tail up submissive posture). Playful contact, which in this species involves gentle nibbling of the posterior cheeks, was more frequently launched by the dominant than by the subordinate. This was not only true at the adult stage, but also at the juvenile stage, before dominance-subordination relationships were sharply polarized. Therefore, it would appear that in the relatively asocial hamster, the subordinates tend to avoid playful contact with dominants. This is markedly different to rats, where the subordinates actively seek out and engage dominants in play. This contrast further supports our hypothesis that subordinate male rats use play as a means of maintaining familiarity with dominants. © 1993 Wiley-Liss, Inc.     

Juvenilized play fighting in subordinate male rats

As pairs of male juvenile sibling rats that are housed together become sexually mature, they develop a dominance-subordinance relationship. These dominance relationships appear to be reflected in the play fighting of the pairmates both as juveniles and as young adults, in that the seemingly subordinate partner initiates more playful attacks at both ages. However, as adults, even though it is the subordinate that initiates more playful attacks, it is the subordinate that is pinned on his back by the partner most often. Dominant pairmates were found to switch to defensive patterns typically found in adult males. In contrast, the subordinates, when contacted on the nape, were more likely to retain the juvenile pattern of turning over to supine. Therefore, the subordinate pairmate of an adult pair of male siblings both initiates more playful attacks and defends itself in a more juvenile manner than its dominant partner, and this leads to it being pinned more frequently. This pattern of behavior by subordinate rats is suggested to function as a friendship maintenance mechanism permitting co-existence in multimale colonies.     

Effects of modelling on children''s pretend play

The effects of modelling on pretend play were studied in children between 2.6 and 3.6 years of age by examining changes both in the action and language-based expressions of pretending. Three modelled scenes were demonstrated with the same realistic toys used by the child in the pre-modelling phase. The results gave support to the idea of the effectiveness of modelling. The effects of the modelled scenes were clearest among children whose pre-modelling play consisted of object-centred actions including few of pretending. The post-modelling play of this subgroup showed better quality of action and language categories and integration measures. Among the decentred players no significant action benefit could be achieved. This might have been an outcome of the contextual limits of the toy material and of the drop of play motivation caused by the model interruption. However, these children expressed verbal pretending revealing significant pre-post effects for inventive utterances.     

Rhesus plasma cortisol response at four dominance positions

Adrenocortical function and social behaviors were measured in 48 laboratory-born juvenile monkeys in stable (original) groupings at rest, in the same groupings in competition for drinking water, in newly formed groupings each composed of animals from the same original dominance position, and upon return to the original groupings, always in groups of four. In newly formed groupings, plasma cortisol measured higher with each step down in the new dominance hierarchy, the effect attenuating by day 8. Although the partial correlation between frequencies of hostility behavior and plasma cortisol level was low (r = 0.05) when holding fear constant, the partial correlation between cortisol and fear behaviors, holding hostility behavior constant, was 0.86. The data provide evidence that corticosteroid elevations during social stress are related to behavior suggestive of fear and not aggression and are dependent upon dominance rank, the level of dominance competition, and previous dominance history.     

Social dominance and the disassociation between explicit and implicit representations of equality

This study tested whether social dominance orientation (SDO) predicted a conceptual disassociation between explicit (declarative or propositional) attitudes about equality and implicit (automatic or associative) views of how representative New Zealand Europeans and Maori are of the New Zealand nation (N = 48 Europeans). Explicitly stated attitudes framing equality in terms of procedural justice or meritocratic treatment were positively correlated with individual differences in the implicit tendency to view New Zealand Europeans as exclusively representative of New Zealand. This tendency to explicitly frame equality as based on individual merit and to implicitly favour the dominant (European) ethnic group as representative of the nation was observed only among people high in SDO. Our analysis provides novel support for the position that meritocratic ideology is malleable and may be employed by those high in SDO to frame concepts of equality and justice in ways that suit their desire for group‐based dominance. Copyright © 2011 John Wiley & Sons, Ltd.     

The inheritance of social dominance rank in red grouse (Lagopus Lagopus scoticus)

Social dominance rank in red grouse has a large inherited component. The relative contributions of mothers and fathers to the dominance ranks of their sons and daughters were studied by breeding a dominant and a subordinate strain and crossing them. Both parents contributed equally to the dominance ranks of both sons and daughters. Cocks from the dominant strain were more aggressive and had bigger combs than cocks from the subordinate strain. Dominant cocks and hens, however, did not weigh more than subordinates.     

Support for exclusionism as an independent dimension of social dominance orientation in mainland China

Three studies using exploratory and confirmatory factor analyses provided consistent evidence for a three-factor model of the social dominance orientation (SDO) in Mainland China. Support for exclusionism, which was not found in previous research, emerged as an independent SDO factor (Studies 1, 2, and 3). In Study 2, this factor predicted SDO difference between a high status group (managers) and a low status group (entry-level employees). In Study 3, this factor correlated positively with authoritarianism and negatively with altruism. These results provided evidence for the validity of this new SDO factor. The findings are discussed in terms of their relations to China's cultural tradition and contemporary economic development.     

The perception of preschool social dominance

Children's and teachers' perception of social dominance was examined using a behavioral criterion for determining accuracy of verbal judgments. Video records of agonistic interactions were obtained during approximately 60 hours of free-play at two preschool centers. Analyses of social conflict episodes ending in submission revealed linear dominance structures for both groups. Dominance perception was assessed in two ways. Both teachers and children were asked to rank-order a subgroup of children according to dominance. They were also asked to select the more dominant children in a number of predetermined pairs. Results indicated that teachers could accurately judge dyadic dominance relations, and that accuracy among children varied as a function of their status within the group hierarchy. Findings have implications for social dominance assessment methodology, and for the issue of consensual versus ecological validity in developmental studies of social perception.     

The intergenerational transmission of social dominance: A three‐generation study

This study examined the transmission of social dominance orientation (SDO) from parents and grandparents to children. It was predicted that parents as well as grandparents would pass their social dominance attitudes to children. Children's levels of SDO would thus be the highest when parental and grandparental attitudes are high; the lowest when parental and grandparental attitudes are low; and intermediate when parental and grandparental attitudes are incongruent. These hypotheses were examined in a sample of 93 families including children (in early adulthood), one of their parents, and one of their grandparents. Results yielded support for the predictions. These findings' implications are discussed in terms of their potential to explain previous inconsistent results on the transmission of social attitudes to children. Copyright © 2008 John Wiley & Sons, Ltd.     

The role of emotion transition for the perception of social dominance and affiliation

Individuals who show anger are rated as higher in dominance and lower in affiliation, whereas those who express sadness are rated lower in dominance and higher in affiliation. Little is known about situations where people show both expressions in sequence as happens when a first emotional reaction is followed by a second, different one. This question was examined in two studies. Overall, we found that the last emotion shown had a strong impact on perceived behavioural intentions. However, the information about the previously shown emotion was also integrated. The specific mode of integration was dependent on the salience of the change and naive theories about the type of person who changes their emotion in the face of changing events.     

Independent and social play among profoundly mentally retarded adults: training, maintenance, generalization, and long-term follow-up.

Play skills were taught to eight profoundly mentally retarded adults in two interrelated experiments. In Experiment 1, a multiple baseline across subjects design was used to assess the efficacy of verbal and physical prompts on independent play. In Experiment 2, the same subjects and experimental procedures were used to develop social play. Verbal prompting and graduated physical guidance procedures were found to be effective in substantially increasing independent play in Experiment 1 and social play in Experiment 2. Positive changes were also observed in collateral behaviors. Inappropriate play decreased slightly and stereotypy decreased to very low levels. Social interaction increased substantially in Experiment 2 when social play was targeted but little change was observed in Experiment 1 when only independent play was targeted. Treatment gains were maintained for 26 weeks in Experiment 1 and 10 weeks in Experiment 2. In addition, the treatment gains were generalized across subjects and settings in Experiment 2. Finally, regular follow-up checks showed that independent and social play remained in the repertoire of the subjects for 12 months following the termination of programmed maintenance.     

Ethnic hierarchies,ethnic prejudice,and social dominance orientation

Previous research in multi‐ethnic societies has shown that people rank, or form hierarchies of, the ethnic groups on the basis of social distance. Based on self‐report data from a community sample (N = 150 non‐psychology students), this study examined (1) the correspondence of ratings and rankings of six ethnic target groups among various subgroups of participants (Swedish and immigrant men and women), and (2) the relationship of inclination to ethnic ranking with ethnic prejudice and social dominance orientation. In accord with our hypotheses, the results disclosed that (1) irrespective of gender and ethnic origin, the various subgroups of participants ranked and formed similar hierarchies of the six ethnic target groups, and (2) people's inclination to ethnic ranking showed significant correlations with their ethnic prejudice as well as social dominance orientation. Copyright © 2005 John Wiley & Sons, Ltd.     

Dominance-subordinance in cohabiting pairs of adult rats: Effects on Aggressive behavior

Following an initial intruder aggression test, 10 pairs of adult male rats matched on aggressiveness were formed. The first 20 min of paired cohabitation were used to determine dominance and subordinance between pau members. Residents judged to be dominant from this observation session gained significantly more weight during cohabitation and exhibited significantly more aggression on the second aggression test than their subordinate counterparts. Significant correlations among various measures of aggression were found, but open field performance did not correlate, with the measures of aggression nor did changes in open field scores reflect changes in aggression.     

Interspecific aggression and reactivity in rats: Effects of selective raphe lesions and additional olfactory bulb ablation

Large depletion of brain 5 HT has been shown to induce mouse-killing behavior in the rat. Selective lesions of the raphe nuclei have been investigated in order to determine whether the various components of the 5 HT system exert some specific control over this aggressive behavior. Electrolytic lesions of the dorsal or the median raphe nucleus do not induce mouse killing, whereas combined lesions of these nuclei elicit this behavior in about 40% of naive rats. Consequently, it appears that serotonergic neurons originating in the dorsal and median raphe nuclei work synergistically in mediating inhibitory control over mouse-killing behavior. Loco-motor activity is increased in novel environments by each of the selective lesions and to a larger extent by combined raphe lesions; 24 hours activity in resting conditions is unchanged during the light period, and increased during the dark period of the daily cycle by the various lesions. As it has been shown previously that hyper-activity in response to novelty following raphe lesions is not directly related to the 5 HT decrease in the brain, it appears that interspecific aggression and motor responsiveness must not be dependent on the same neural substrate within the raphe nuclei. The raphe lesions do not facilitate the elicitation of mouse killing by further olfactory bulb ablations, in contrast to earlier results where bulbectomy facilitated the induction of this behavior by raphe lesions.