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The article proposes a radical distinction in understanding human aggression and violence. It will seek to comprehend aggression as an inextricable and also valuable part of life. At the same time, it must be shown that human violence has nothing to do with a vital necessity but is a policy based on the assumption and imposition of a hierarchical conception of existence, from which domination and delegitimization relationships are built, devaluing the "subalterns". This perspective will be imposed by force to later be rationalized, normalized, and legitimized to the extent that in many situations violence ceases to be consciously perceived as such. Those who hold power arrogate to themselves the right to define what is to be considered violent and what will not be, imposing on the victims a double submission through the pedagogy of cruelty. [ABSTRACT FROM AUTHOR]

Simple Summary: Animals often inflict bite wounds in laboratory housing, compromising animal welfare and, potentially, experimental results. For example, 1.5–14% of male laboratory mice (Mus musculus) obtain bite wounds over the course of a year. Recently, spiny mice (Acomys cahirinus) have become more popular in laboratory research for their regenerative healing and menstrual cycling, but we noticed frequent severe wounding in males and females in our colony—likely related to their relatively weak skin. Thus, we recorded the frequency and severity of bite wounding in our colony for one year and found that 46% of spiny mice had at least one bite wound, regardless of sex. The bite wounds in females were less severe, with single wounds on the rump, while males more often had multiple wounds on their anterior and rump. In a separate study, both sexes established stable dominance structures, with most of the fights occurring at the start of the active/dark cycle. Aged animals greater than 22 months old were never observed fighting, and the study on bite wounding suggested they also do not inflict bite wounds. These results have implications for both spiny mouse welfare and experimental results using spiny mice since repeated physical trauma can affect healing and menstrual cycling in mice and humans. Bite wounds due to aggression in male laboratory mice (Mus musculus) are a major welfare concern, often leading to attrition, chronic activation of the innate immune system, and significant impacts on the experimental results derived from the use of these animals as models. Bite wounding within the home-cage of spiny mice (Acomys cahirinus)—a valuable research model for wound healing and menstruation—is poorly characterized. While we have anecdotally observed frequent bite wounding in Acomys, the frequency of aggression within the home-cage, the severity of the bite wounds, and the types of dominance structures remain unstudied. Here, we report that 46% of Acomys cages in our colony had at least one bite wound over the course of a year and that same-sex pairs fought in the home-cage 10% of the time during their dark/active phase. Both sexes inflicted wounds and frequently engaged in agonistic behaviors, even with stable dominance structures. We found that females inflicted less severe bite wounds in same-sex housing. Also, aged females in same-sex pairs were never observed fighting, and no bite wounds were observed in aged Acomys. These results suggest that we should consider whether bite wounding negatively impacts our experimental results since physical trauma is known to alter menstrual cycling and healing. [ABSTRACT FROM AUTHOR]

The current study explored a form of femmephobia (specifically, negative attitudes toward femininity in men) as a predictor of anti-gay behaviors among a sample of heterosexual men (N = 417). Additional predictor variables included hierarchical worldviews (i.e., social dominance orientation, right-wing authoritarianism, narcissism) and prejudicial attitudes (i.e., old-fashioned and modern homonegativity). Femmephobia emerged as a robust predictor, accounting for 23% of the variance in anti-gay behavior, surpassing the explanatory power (15%) of all other considered variables combined. Moreover, social dominance only predicted anti-gay behavior when femmephobia levels were high. Future research on discrimination and violence related to sexual identity and gender expression should incorporate femmephobia as a key predictive factor. [ABSTRACT FROM AUTHOR]

Within social dominance hierarchies, rank has a major impact on health and fitness. Dominance hierarchies are rarely stable as individuals may change rank due to changes in the social environment. Here we describe general group-level social network properties and changes in social ties and behavior during rank transitions in 16 communities of the cichlid Astatotilapia burtoni. Social networks based on chases were dense with dominant males frequently chasing subordinate males and females. This intense territoriality of dominant males was also reflected by a high degree of 'power' inequality. Compared to chase-based networks, display-based networks were characterized by a high degree of reciprocity due to display behaviors mostly occurring bidirectionally among a few highly ranked males. Territory ownership is tightly linked to social dominance and territory loss (i.e., social descent) was, as expected, associated with a sharp reduction in aggression level and an increase in chases received. However, although territory acquisition (i.e., social ascent) was an abrupt process, ascending males displayed elevated aggression prior to ascent, in sharp contrast to previous studies carried out in less complex settings. Together, our results provide novel insights into dynamic changes in behavior in cichlid dominance hierarchies. [ABSTRACT FROM AUTHOR]

Dominance relationships between males and their associated traits are usually heritable and have implications for sexual selection in animals. In particular, social dominance and its related male pheromones are heritable in inbred mice; thus, we wondered whether epigenetic changes due to altered levels of DNA methylation determine inheritance. Here, we used C57BL/6 male mice to establish a social dominance–subordination relationship through chronic dyadic encounters, and this relationship and pheromone covariation occurred in their offspring, indicative of heritability. Through transcriptome sequencing and whole-genome DNA methylation profiling of the sperm of both generations, we found that differential methylation of many genes was induced by social dominance–subordination in sires and could be passed on to the offspring. These methylated genes were mainly related to growth and development processes, neurodevelopment, and cellular transportation. The expression of the genes with similar functions in whole-genome methylation/bisulfite sequencing was also differentiated by social dominance–subordination, as revealed by RNA-seq. In particular, the gene Dennd1a, which regulates neural signaling, was differentially methylated and expressed in the sperm and medial prefrontal cortex in paired males before and after dominance–subordination establishment, suggesting the potential epigenetic control and inheritance of social dominance-related aggression. We suggest that social dominance might be passed on to male offspring through sperm DNA methylation and that the differences could potentially affect male competition in offspring by affecting the development of the nervous system. [ABSTRACT FROM AUTHOR]

Interspecific dominance interactions have consequences for behavior, ecology, and the stability of species coexistence. Determinants of the outcomes of these interspecific interactions are therefore of great interest. However, few large-scale comparative works have demarcated the potential behavioral and morphological traits that explain dominance between species. To delineate which traits may influence species dominance, we rely on a newly established dominance ranking of bird species in North America. We pair these dominance rankings with phylogenetic analysis and incorporate social, morphological, and natural history variables to determine how morphological and social traits contribute. Like previous studies, we find that body mass is a positive predictor of dominance, but we also find that after controlling for body mass, bill length positively predicts a species' rank in the hierarchy. In addition to morphological traits, we find that species that engage in proportionally more intraspecific fights tend to be less interspecifically dominant. Consequently, both morphological and social variables influence the interspecific dominance rank of a species. Such effects may have downstream consequences for the acquisition of foraging resources and the evolution of a species. [ABSTRACT FROM AUTHOR]

Simple Summary: When male mice are kept in groups at animal facilities, aggressive interactions between cage mates are not uncommon. Systematically reviewing previous studies that explored the cause of male mice aggression, we found that studies were disparate, using several different strains, a diverse set of environmental enrichments and different ways of grouping and housing mice, as well as different ways to observe aggression. Understanding the cause of male mice aggression is difficult when researchers use different methods and study designs. Nevertheless, our results suggest that home cage aggression is best studied in home cage environments and not by introducing unfamiliar mice to each other in a novel environment. In addition, while we were able to provide recommendations on how to minimize aggression, our assessment was that there is no universal solution that could be used by all animal facilities. Instead, it is important to realize that aggression is complex and that animal facilities might have to try different possible solutions to find what works best under their specific conditions. Aggression among group-housed male mice is a major animal welfare concern often observed at animal facilities. Studies designed to understand the causes of male mice aggression have used different methodological approaches and have been heterogeneous, using different strains, environmental enrichments, housing conditions, group formations and durations. By conducting a systematic literature review based on 198 observed conclusions from 90 articles, we showed that the methodological approach used to study aggression was relevant for the outcome and suggested that home cage observations were better when studying home cage aggression than tests provoking aggression outside the home cage. The study further revealed that aggression is a complex problem; one solution will not be appropriate for all animal facilities and all research projects. Recommendations were provided on promising tools to minimize aggression, based on the results, which included what type of environmental enrichments could be appropriate and which strains of male mice were less likely to be aggressive. [ABSTRACT FROM AUTHOR]

Methamphetamine (METH) abuse is associated with a spectrum of behavioral consequences, among which heightened aggression presents a significant challenge. However, the causal role of METH's impact in aggression and its target circuit mechanisms remains largely unknown. We established an acute METH exposure-aggression mouse model to investigate the role of ventral tegmental area (VTA) dopaminergic neurons and ventral medial hypothalamus VMH glutamatergic neuron. Our findings revealed that METH-induced VTA dopamine excitability activates the ventromedial hypothalamus (VMH) glutamatergic neurons, contributing to pathological aggression. Notably, we uncovered a dopaminergic transmission within the VTA-VMH circuit that exclusively functioned under METH influence. This dopaminergic pathway emerged as a potential key player in enabling dopamine-related pathological aggression, with heightened dopaminergic excitability implicated in various psychiatric symptoms. Also, the modulatory function of this pathway opens new possibilities for targeted therapeutic strategies for intervention to improve treatment in METH abuse and may have broader implications for addressing pathological aggression syndromes. • Elevated VTA dopaminergic excitability emerges as a key contributor to METH-induced aggression. • Dopamine presence in the VMH is exclusive to METH influence. • The VTA-VMH circuit is engaged, playing a dual role in both the development and modulation of METH-induced aggression. [ABSTRACT FROM AUTHOR]

Group-living primates exhibit variable reactions to intergroup encounters (or IGEs), reflecting species-specific strategies and individual motivations. In chimpanzees (Pan troglodytes), dominating in IGEs provides fitness benefits. Less is known about responses to IGEs in bonobos (Pan paniscus) despite their equal relevance for understanding the origins of human intergroup relations. We observed the Bompusa West (WBp) bonobo community at LuiKotale during a 2-month shift in ranging resulting in frequent IGEs with the smaller Bompusa East (EBp) community. We tested whether incursions provided ecological benefits, and whether responses to IGEs were consistent with inter-community dominance or tolerance. We measured fruit availability and collected activity scans from 26 mature WBp community members when in their core ranging area, during incursions into the EBp ranging area, and during IGEs. We collected data on sexual interactions and aggression with in-group and out-group members during 19 independent IGEs. During their shift in ranging, fruit availability was greater in the EBp ranging area, and WBp bonobos consumed more fruit during incursions than when in their core ranging area. Coalitionary intergroup aggression occurred during nine IGEs, and outcomes were consistent with imbalances in fighting power, in that larger WBp parties supplanted smaller EBp parties from the immediate area. However, communities reformed associations following 70% of coalitionary conflicts, and prolonged IGEs facilitated out-group sexual interactions and female transfers. The WBp community shift in ranging was likely motivated by ecological factors and responses to increased IGEs reflected a mixture of competitive and tolerant strategies. [ABSTRACT FROM AUTHOR]

Social hierarchies are often found in group‐living animals and can be formed through pairwise aggressive interactions. The dominance rank can influence reproductive success (RS) with a skew towards high‐ranking individuals.Using game theory, we investigate how the opportunity for differently ranked individuals to achieve RS influences the costs of hierarchy formation and the strength of winner and loser effects.In our model, individuals adjust their aggressive and submissive behaviour towards others through reinforcement learning. The learning is based on rewards and penalties, which depend on relative fighting ability. From individual‐based simulations, we determine evolutionary equilibria of traits such as learning rates. We examine situations that differ in the extent of monopolisation of contested RS by dominants and in the proportion of total RS that is contested.The model implements two kinds of fighting costs: a decrease in effective fighting ability from damage (loss of condition) and a risk of mortality that increases with the total accumulated damage. Either of these costs can limit the amount of fighting.We find that individuals form stable dominance hierarchies, with a positive correlation between dominance position and fighting ability. The accumulated costs differ between dominance positions, with the highest costs paid by low or intermediately ranked individuals. Costs tend to be higher in high‐skew situations.We identify a 'stay‐in, opt‐out' syndrome, comprising a range from weaker (stay‐in) to stronger (opt‐out) winner–loser effects. We interpret the opt‐out phenotype to be favoured by selection on lower ranked individuals to opt out of contests over social dominance, because it is more pronounced when more of the total RS is uncontested.We discuss our results in relation to field and experimental observations and argue that there is a need for empirical investigation of the behaviour and reproductive success of lower ranked individuals. [ABSTRACT FROM AUTHOR]

Why some people, and not others, exhibit aggression remains unknown. Research points to certain personality traits being linked to either proactive or reactive aggression, or both. The current study attempts to address these gaps from the perspective of revised Reinforcement Sensitivity Theory (rRST). Using 146 participants, results revealed Behavioral Approach System (BAS)-Impulsivity and the Behavioral Inhibition System (BIS) predicted proactive and reactive aggression. Defensive Fight predicted reactive aggression. BAS-Impulsivity predicted proactive aggression partially mediated by Social Dominance Orientation. These findings suggest proactive and reactive aggression are motivated by a combination of anxiety and rapid, approach-motivational personality traits. This study provides further understanding of the specific relations between rRST and aggression, is integrated into the general aggression model, and has implications for treatment of aggressive individuals. [ABSTRACT FROM AUTHOR]

Strong, stable social bonds in primates are characterized by high levels of social affiliation, low levels of aggression, minimal stress, and affiliative reciprocity within the dyad. In relatively well‐studied catarrhine monkeys, these bonds tend to form most frequently between kin, animals close in age, and animals close in rank. This results in patterns of affiliation in which kin, similarly aged animals, and like‐ranked animals tend to affiliate and patterns of aggression and submission where animals tend to aggress more toward nonkin and closely ranked animals, and submit more toward distantly ranked animals. However, literature on how affiliative and agonistic relationships are organized in platyrrhine primate species like brown capuchin monkeys is limited and conflicting. In this study, we used social network analyses to characterize how age, sex, maternal kinship, and dominance rank relate to the patterns of submissive, aggressive, contact, and grooming interactions in a group of captive brown capuchin monkeys. Like catarrhine monkeys, brown capuchin monkeys showed a steep linear dominance hierarchy, tended to affiliate with kin, similarly aged animals, and like‐ranked animals, and tended to aggress more toward nonkin. However, our monkeys showed a pattern of affiliation and grooming down the hierarchy that is inconsistent with grooming up the hierarchy patterns often seen in catarrhine monkey groups, suggesting that brown capuchins do not compete for access to higher ranking social partners. Higher ranking monkeys were most central to the aggression network, and lower ranking monkeys were most central to the submission network. Mid‐ranking monkeys were the most central to the contact network, suggesting that they may play an important role in the affiliative cohesion of the group. These results inform our understanding of brown capuchin social behavior specifically, and of how demographic factors relate to social organization in platyrrhine primates generally. Highlights: Captive brown capuchins show a steep linear dominance hierarchy.Rank differentially predicts who is the most central across networks: High‐rankers for aggression, low‐rankers for submission, & mid‐rankers for contact.They affiliate with kin, similarly aged and like‐ranked animals, & aggress to nonkin. [ABSTRACT FROM AUTHOR]

Animal groups are often organized hierarchically, with dominant individuals gaining priority access to resources and reproduction over subordinate individuals. Initial dominance hierarchy formation may be influenced by multiple interacting factors, including an animal’s individual attributes, conventions and self-organizing social dynamics. After establishment, hierarchies are typically maintained over the long-term because individuals save time, energy and reduce the risk of injury by recognizing and abiding by established dominance relationships. A separate set of behaviours are used to maintain dominance relationships within groups, including behaviours that stabilize ranks (punishment, threats, behavioural asymmetry), as well as signals that provide information about dominance rank (individual identity signals, signals of dominance). In this review, we describe the behaviours used to establish and maintain dominance hierarchies across different taxa and types of societies. We also review opportunities for future research including: testing how self-organizing behavioural dynamics interact with other factors to mediate dominance hierarchy formation, measuring the long-term stability of social hierarchies and the factors that disrupt hierarchy stability, incorporating phenotypic plasticity into our understanding of the behavioural dynamics of hierarchies and considering how cognition coevolves with the behaviours used to establish and maintain hierarchies. This article is part of the theme issue ‘The centennial of the pecking order: current state and future prospects for the study of dominance hierarchies’. [ABSTRACT FROM AUTHOR]

Dominance is important for access to resources. As dominance interactions are costly, individuals should be strategic in whom they interact with. One hypothesis is that individuals should direct costly interactions towards those closest in rank, as they have most to gain—in terms of attaining or maintaining dominance—from winning such interactions. Here, we show that male vulturine guineafowl (Acryllium vulturinum), a gregarious species with steep dominance hierarchies, strategically express higher-cost aggressive interactions towards males occupying ranks immediately below themselves in their group’s hierarchy. By contrast, lower-cost aggressive interactions are expressed towards group members further down the hierarchy. By directly evaluating differences in the strategic use of higher- and lower-cost aggressive interactions towards competitors, we show that individuals disproportionately use highest-cost interactions—such as chases—towards males found one to three ranks below themselves. Our results support the hypothesis that the costs associated with different interaction types can determine their expression in social groups with steep dominance hierarchies. This article is part of the theme issue ‘The centennial of the pecking order: current state and future prospects for the study of dominance hierarchies’. [ABSTRACT FROM AUTHOR]

Dominance behaviours have been collected for many groups of animals since 1922 and serve as a foundation for research on social behaviour and social structure. Despite a wealth of data from the last century of research on dominance hierarchies, these data are only rarely used for comparative insight. Here, we aim to facilitate comparative studies of the structure and function of dominance hierarchies by compiling published dominance interaction datasets from the last 100 years of work. This compiled archive includes 436 datasets from 190 studies of 367 unique groups (mean group size 13.8, s.d. = 13.4) of 135 different species, totalling over 243 000 interactions. These data are presented in an R package alongside relevant metadata and a tool for subsetting the archive based on biological or methodological criteria. In this paper, we explain how to use the archive, discuss potential limitations of the data, and reflect on best practices in publishing dominance data based on our experience in assembling this dataset. This archive will serve as an important resource for future comparative studies and will promote the development of general unifying theories of dominance in behavioural ecology that can be grounded in testing with empirical data. This article is part of the theme issue ‘The centennial of the pecking order: current state and future prospects for the study of dominance hierarchies’. [ABSTRACT FROM AUTHOR]

A century ago, foundational work by Thorleif Schjelderup-Ebbe described a ‘pecking order’ in chicken societies, where individuals could be ordered according to their ability to exert their influence over their group-mates. Now known as dominance hierarchies, these structures have been shown to influence a plethora of individual characteristics and outcomes, situating dominance research as a pillar of the study of modern social ecology and evolution. Here, we first review some of the major questions that have been answered about dominance hierarchies in the last 100 years. Next, we introduce the contributions to this theme issue and summarize how they provide ongoing insight in the epistemology, physiology and neurobiology, hierarchical structure, and dynamics of dominance. These contributions employ the full range of research approaches available to modern biologists. Cross-cutting themes emerging from these contributions include a focus on cognitive underpinnings of dominance, the application of network-analytical approaches, and the utility of experimental rank manipulations for revealing causal relationships. Reflection on the last 100 years of dominance research reveals how SchjelderupEbbe’s early ideas and the subsequent research helped drive a shift from an essentialist view of species characteristics to the modern recognition of rich inter-individual variation in social, behavioural and physiological phenotypes. This article is part of the theme issue ‘The centennial of the pecking order: current state and future prospects for the study of dominance hierarchies’. [ABSTRACT FROM AUTHOR]

A major challenge in the study of animal communication is distinguishing whether signals convey honest or dishonest information. Biologists infer the honesty of a signal from its correlation with the information being signalled (e.g. fecundity or fighting ability)—the better the correlation, the more honest the signal.However, this view of signalling potentially conflates unreliable indicators with dishonest signals. Just because a trait conveys unreliable information does not mean that the structure serves as a dishonest signal; developmental noise, genetic drift and environmental constraints can reduce the covariation between a putative signal and an organism's quality. Moreover, a trait must influence the behaviour of other organisms to qualify as a signal.We studied how a putative signal, claw size, affects physical performance and social dominance in three species of stream‐dwelling crayfish, which fight routinely over resources. For comparison, we measured the relationship between claw size and claw strength in three species of burrowing crayfish, which do not fight.In all species, crayfish with larger claws were not necessarily stronger, indicating that claw size poorly indicates claw strength. However, claw size is unlikely to function as a dishonest signal of fighting ability in these species for two reasons. First, claw size unreliably indicates claw strength in both the stream‐dwelling species and the burrowing species. Second, relative claw size poorly predicted whether stream‐dwelling crayfish would escalate aggression, questioning whether claw size serves as a signal. Instead, stream‐dwelling crayfish escalated aggression based on their relative body size.Our results highlight the importance of observing behaviour when determining the honesty of a signal. As such, future studies must distinguish between phenotypes that are unreliable indicators (or reliable indicators) from phenotypes that have been selected for dishonest (or honest) signalling. A free Plain Language Summary can be found within the Supporting Information of this article. [ABSTRACT FROM AUTHOR]

Invasive species are one of the greatest threats to freshwater ecosystems globally. However, the causal mechanisms that drive negative impacts of many invasive species are poorly understood. In Tanzania, non-native Nile tilapia (Oreochromis niloticus) exists in sympatry with a diverse range of native species, many of which are congenerics with strong niche overlap. It has been suggested that O. niloticus can displace native species from preferred habitat through dominance during interference competition, yet interference competition between O. niloticus and a native tilapia species has never been directly tested under experimental conditions. In this study juvenile O. niloticus and Manyara tilapia (Oreochromis amphimelas), a functionally similar but endangered Tanzanian cichlid, were size matched in conspecific and heterospecific pairs. We presented pairs with limited shelter and recorded competitive interactions. We found that O. niloticus were more aggressive and faster to initiate agonistic interactions than O. amphimelas. Furthermore, O. niloticus showed a strong competitive dominance in their interactions with O. amphimelas. One-sided dominance hierarchies can drive fundamental changes in resource use by subordinate individuals, potentially resulting in habitat displacement over the long term. Based on this experimental evidence, we conclude that O. niloticus may threaten native tilapia species through dominance in interference competition. [ABSTRACT FROM AUTHOR]

We addressed whether narcissism and self-esteem synergize to enhance assertive responses and deter aggressive responses to ego-threatening provocation. Participants (N = 448) completed measures of narcissism and self-esteem, imagined ego-threatening provocation, and indicated their aggressive and assertive responses. Participants also completed individual difference measures of agreeableness, openness, status/dominance motivation, and endorsement of the notion that aggression begets power. Narcissism and self-esteem interacted to reduce aggressive responses but enhance assertive responses to ego-threat; moreover, this interaction related to enhanced agreeableness, openness, status/dominance motivation, and reduced endorsement of the belief that aggression begets power, and these relations accounted, in part, for relations between the interaction and aggressive and assertive responses. Broadly, the findings contribute to the contentious issue of how self-evaluation influences responses to ego-threat; specifically, we would suggest that this issue be conceptualized in terms of synergistic effects of narcissism and self-esteem and distinguish between assertive versus aggressive responding. [ABSTRACT FROM AUTHOR]

Research has consistently demonstrated that faces manipulated to appear more masculine are perceived as more dominant. These studies, however, have used forced‐choice paradigms, in which a pair of masculinized and feminized faces was presented side by side. These studies are susceptible to demand characteristics, because participants may be able to draw the conclusion that faces which appear more masculine should be rated as more dominant. To prevent this, we tested if dominance could be perceived when masculinized or feminized faces were presented individually for only 100 ms. We predicted higher dominance ratings to masculinized faces and better memory of them in a surprise recognition memory test. In the experiment, 96 men rated the physical dominance of 40 facial photographs (masculinized = 20, feminized = 20), which were randomly drawn from a larger set of faces. This was followed by a surprise recognition memory test. Half of the participants were assigned to a condition in which the contours of the facial photographs were set to an oval to control for sexual dimorphism in face shape. Overall, men assigned higher dominance ratings to masculinized faces, suggesting that they can appraise differences in facial sexual dimorphism following very brief exposure. This effect occurred regardless of whether the outline of the face was set to an oval, suggesting that masculinized internal facial features were sufficient to affect dominance ratings. However, participants' recognition memory did not differ for masculinized and feminized faces, which could be due to a floor effect. [ABSTRACT FROM AUTHOR]

• Hamsters show sex differences in the formation of dominance relationships. • Dominance relationships are less stable in female compared to male hamsters. • Dominance status creates sex differences in status-dependent neural plasticity. Dominance relationships are identified by changes in agonistic behavior toward specific individuals. While there are considerable individual and species differences in dominance relationships, sex differences are poorly understood in rodent models because aggression among female rodents is rare. The aim of this study was to characterize sex differences in the formation and maintenance of dominance relationships in same-sex pairs of male and female Syrian hamsters. We pooled data from multiple projects in our lab to evaluate dominance interactions in 68 male dyads and 88 female dyads. In each project, animals were matched with a partner similar in age, sex, and estrous cycle and we exposed animals to daily social encounters for two weeks in a resident-intruder format. We found that female hamsters were quicker to attack and attacked at higher rates compared to males regardless of dominance status. In addition, resident female hamsters were quicker to attack and attacked at higher rates than intruder females, but aggression in males did not depend on residency status. Female subordinates were quicker to submit and fled at higher rates from their dominant counterparts compared to male subordinates. Intruder subordinate females were quicker to submit and fled at higher rates than resident subordinate females. Females were also more resistant than males to becoming subordinate in that they fought back more consistently and were more likely to reverse their dominance status. These findings indicate that dominance relationships are less stable in females compared to males and that residency status has a larger impact on agonistic behavior in females than males. Overall, differences in how males and females display territorial aggression can lead to sex differences in the establishment and maintenance of dominance relationships. [ABSTRACT FROM AUTHOR]

This narrative review article summarizes the current state of knowledge regarding the relationship between the endocannabinoid system (ECS) and aggression across multiple vertebrate species. Experimental evidence indicates that acute administration of phytocannabinoids, synthetic cannabinoids, and the pharmacological enhancement of endocannabinoid signaling decreases aggressive behavior in several animal models. However, research on the chronic effects of cannabinoids on animal aggression has yielded inconsistent findings, indicating a need for further investigation. Cannabinoid receptors, particularly cannabinoid receptor type 1, appear to be an important part of the endogenous mechanism involved in the dampening of aggressive behavior. Overall, this review underscores the importance of the ECS in regulating aggressive behavior and provides a foundation for future research in this area. • Endocannabinoid system plays a role in aggression as demonstrated by pharmacological and genetic manipulations. • Acute activation of cannabinoid receptors reduces aggression in multiple vertebrate species. • Chronic treatment with cannabinoids on animal aggression has yielded inconsistent findings. • Evidence suggests that CB1 receptors play a role in brain process responsible for dampening aggressive behavior. [ABSTRACT FROM AUTHOR]

During aggression, animals signal their physical abilities to deter opponents from fighting. Competitors that have a coevolved system of communication can resolve the outcome of a fight without paying the cost of engaging in potentially injurious fighting. Invasive species complicate the dynamics of competition, because such species may not have a coevolved system of communication. For example, many species of crayfish have invaded freshwater ecosystems, where they compete with species never encountered before. We studied the traits used to escalate aggression within and between two species of invasive crayfish in Arizona, Procambarus clarkii and Faxonius virilis. Through staged encounters, we found that individuals of both species escalated aggression according to their relative claw size. Furthermore, claw size (instead of claw strength) determined the outcome of interactions that escalated to physical combat. Despite P. clarkii and F. virilis presumably not having a coevolved system of communication, claw size predicted the outcome of interspecific aggression. In crayfish and other species that have invasive potential, future investigations into intraspecific versus interspecific communication dynamics are warranted as they may shed light on the successes and failures of past and present species introductions. • We studied traits used to escalate aggression in two species of invasive crayfish. • Both species escalated and resolved disputes using their claws as signals. • Claw size determined the outcome of interactions that escalated to physical combat. • Species' ability to communicate with competitors may affect invasive potential. [ABSTRACT FROM AUTHOR]

A-holes threaten the overall well-being of many social systems. This study explicates, constructs, and validates a measure for a-holism in relational communication. We identified and constructed items for four dimensions of the a-holism construct: verbal aggression, dominance, entitlement, and resistance to feedback. An online survey was distributed to 315 adults about their perceptions of a-holes they have met in their lives and how they communicated. The a-holism scale demonstrated second order uni-dimensionality. There was also evidence for convergent and discriminant validity. Implications for application of the a-holism scale in relational communication are discussed. [ABSTRACT FROM AUTHOR]

Intergroup encounters are common in nonhuman primates and can vary from affiliative to aggressive. We extracted data from the literature to test five different hypotheses: 1) where there are group size differences between opposing groups, whether the larger group is more likely to win an intergroup encounter than the smaller group; 2) whether the likelihood of a group engaging in aggressive intergroup encounters increases with group size; and 3–5) whether dominant, older individuals, and/or males are more likely to participate aggressively in intergroup encounters than subordinate, younger individuals and/or females. Our data set comprised 52 studies on 31 primate species (3 lemur species, 5 New World monkeys, 19 Old World monkeys, and 4 apes). We found that the larger group is more likely to win an encounter against a smaller group than vice versa. We found no significant relationship between group size and propensity to be aggressive during intergroup encounters. We found weak/no support for the effect of age, dominance rank, and sex on the frequency of aggression displayed toward outgroup individuals during intergroup encounters. Species- and population-specific differences in inter- and intragroup competition and in the degree of the unequal distribution of resources across group members may explain why age, dominance rank, and sex are not strong predictors of aggression during intergroup encounters. [ABSTRACT FROM AUTHOR]

Previous work has shown that during adolescence, classrooms vary greatly in the extent to which aggression is rewarded with popularity (the 'popularity norm'). Aggressive popularity norms may promote the proliferation of aggression and negatively affect the classroom climate. It is, however, unknown how these norms emerge in the first place. This longitudinal study therefore investigated whether aggressive popularity norms can be predicted by the classroom composition of students. We examined whether the prevalence of six student types - socially and non-socially dominant prosocial, aggressive, and bi-strategic adolescents (adolescents who are both highly prosocial and aggressive) - contributed to the norm by establishing a popularity hierarchy: strong classroom asymmetries in popularity. We collected peer-nominated data at three secondary schools in the Netherlands (SNARE-study; Nstudents = 2843; Nclassrooms = 120; 51.4% girls; Mage = 13.2). Classroom-level regression analyses suggest that the classroom percentage of socially dominant aggressive and bi-strategic students predicted higher aggressive popularity norms, both directly and by enhancing the classrooms' popularity hierarchy. Instead, the presence of non-socially dominant aggressive students and socially dominant prosocial students contributed to lower aggressive popularity norms. Socially dominant prosocial students also buffered against the role of socially dominant aggressive adolescents in the aggressive popularity norm (moderation), but not against bi-strategic adolescents' role. Our findings indicate that interventions aimed at reducing aggressive popularity norms should first and foremost take the composition of classrooms at the start of the school year into account; and should not only encourage prosocial behavior, but also actively discourage aggression. [ABSTRACT FROM AUTHOR]

Interfemale competition regimes in primate societies have been described as despotic or egalitarian based on female social behaviour. Hierarchies and nepotism are typical of despotic primates, where dominance rank and kinship are known to be strong drivers of who grooms whom and who fights with whom. However, a general theory for what structures female–female interactions in egalitarian societies remains underdeveloped. We present two nonmutually exclusive hypotheses that each propose a mechanism for levelling social advantages in a group by conferring social favour to all or most females over time: transitory states (age, residency status and reproductive state) bias social interactions and/or reciprocity governs social interactions. In this study, we (1) determined that a group of red colobus monkeys, Procolobus rufomitratus tephrosceles , in Kibale National Park, Uganda, are highly egalitarian; (2) tested our hypotheses for how egalitarianism may be maintained in this group; and (3) analysed findings across primate studies for support for either hypothesis. In red colobus, agonistic interactions were predicted by age – a transitory state – and transitory states and reciprocity predicted grooming interactions: avid groomers, older females and short-term resident females received more grooming. In addition, behavioural indicators of social status (aggression given and grooming received) were not associated with reproductive success in red colobus, as might be expected in an egalitarian group where variance in fitness should be low. Across primates, we found that transitory states commonly structure social interactions in egalitarian societies but not in despotic societies and that reciprocity is highly variable, especially among egalitarian societies. Rotating social advantage as females shift among transitory states and/or reciprocate grooming may lower interfemale skew in social benefits and potentially in lifetime reproductive success in egalitarian groups, setting them apart from despotic societies where dominance hierarchies and kinship maintain a more static and unequal distribution of social advantage. • In egalitarian primates, transitory states like age bias female social interactions. • In a highly egalitarian primate, transitory states and reciprocity both bias grooming. • Bias by transitory states or reciprocity can equalize social advantage over time. • In despotic primates, dominance and kinship override transitory states. • Grooming reciprocity spans a wider range in egalitarian than despotic primates. [ABSTRACT FROM AUTHOR]

Research has indicated that men's facial width-to-height ratio (fWHR) is part of an evolved system of social dominance, aggression, and power. fWHR has been linked to antisocial behavior, measured by self-reported aggression, but recent studies have failed to replicate this finding. To overcome these inconsistencies, influencing factors such as social status have to be taken into account in order to explain the relationship between fWHR and aggression. In particular, income has been shown to be an important influencing factor in this relationship. Furthermore, previous findings suggested that testosterone is linked to fWHR and might be associated with fWHR and dominance-related outcomes. Therefore, this study examined the influence of both social status defined by income and salivary testosterone on the association between fWHR and self-reported dominance-related behavioral traits. In particular, links between fWHR and self-report measures of aggression and the Dark Triad (encompassing psychopathy, Machiavellianism, and narcissism) were investigated in N = 109 men aged 40 to 75 years. fWHR was significantly associated with physical aggression and two of the Dark Triad traits (psychopathy and Machiavellianism) in men reporting low income. The relationship between fWHR and narcissism was moderated by testosterone. The findings highlight the importance of considering social status and neuroendocrine parameters such as testosterone when examining associations between fWHR and complex psychological traits and behaviors. [ABSTRACT FROM AUTHOR]

Intraspecific social dominance hierarchies should be influenced by environmental variation; however, in colour polymorphic species, dominance hierarchies are often assumed fixed, and thus insensitive to environmental variability. We ran a series of experiments using the colour polymorphic long-tailed brush lizard (Urosaurus graciosus) to challenge this assumption. We staged contests between orange and yellow morph males over a single heated perch, two perches at the same temperature, or two perches differing in temperature. Our first experiment revealed that orange-throated males are socially dominant. However, this hierarchy collapsed in our other experiments as yellow males became more aggressive. Interestingly, both males only ever secured their own perch where the perches differed in temperature. These findings mirror observations of morph behavioural flexibility in nature and studies of behaviour-environment interactions in non-polymorphic taxa. We conclude that colour morphs may have an underappreciated ability to assess resource-level changes and respond with concomitant flexibility in behaviour. [ABSTRACT FROM AUTHOR]

The enzyme steroid 5α-reductase 2 (5αR2) catalyzes the conversion of testosterone into the potent androgen 5α-dihydrotestosterone. Previous investigations showed that 5αR2 is expressed in key brain areas for emotional and socio-affective reactivity, yet the role of this enzyme in behavioral regulation remains mostly unknown. Here, we profiled the behavioral characteristics of 5αR2 heterozygous (HZ) and knockout (KO) mice, as compared with their wild-type (WT) littermates. While male 5αR2 KO mice displayed no overt alterations in motoric, sensory, information-processing and anxiety-related behaviors, they exhibited deficits in neurobehavioral correlates of dominance (including aggression against intruders, mating, and tube dominance) as well as novelty-seeking and risk-taking responses. Furthermore, male 5αR2 KO mice exhibited reduced D 2 -like dopamine receptor binding in the shell of the nucleus accumbens – a well-recognized molecular signature of social dominance. Collectively, these results suggest that 5αR2 is involved in the establishment of social dominance and its behavioral manifestations. Further studies are warranted to understand how the metabolic actions of 5αR2 on steroid profile may be implicated in social ranking, impulse control, and the modulation of dopamine receptor expression in the nucleus accumbens. [ABSTRACT FROM AUTHOR]

Research from a variety of disciplines suggests a positive relationship between Western cultural sexualization and women's likelihood of suffering harm. In the current experiment, 157 young men were romantically rejected by a sexualized or non-sexualized woman then given the opportunity to blast the woman with loud bursts of white noise. We tested whether the activation of sexual goals in men would mediate the relationship between sexualization and aggressive behavior after romantic rejection. We also tested whether behaving aggressively toward a woman after romantic rejection would increase men's feelings of sexual dominance. Results showed that interacting with a sexualized woman increased men's sex goals. Heightened sex goal activation, in turn, predicted increased aggression after romantic rejection. This result remained significant despite controlling for the effects of trait aggressiveness and negative affect. The findings suggest that heightened sex goal activation may lead men to perpetrate aggression against sexualized women who reject them. [ABSTRACT FROM AUTHOR]

Dominance is defined as the preferential access to limited resources. The present study aimed to characterise dominance in a non-aggressive flatfish species, the Senegalese sole (Solea senegalensis) by 1) identifying dominance categories and associated behaviours and 2) linking dominance categories (dominant and subordinate) with the abundance of selected mRNA transcripts in the brain. Early juveniles (n = 74, 37 pairs) were subjected to a dyadic dominance test, related to feeding, and once behavioural phenotypes had been described the abundance of ten selected mRNAs related to dominance and aggressiveness was measured in the brain. Late juveniles were subjected to two dyadic dominance tests (n = 34, 17 pairs), related to feeding and territoriality and one group test (n = 24, 4 groups of 6 fish). Sole feeding first were categorized as dominant and sole feeding second or not feeding as subordinate. Three social behaviours (i. “Resting the head” on another fish, ii. “Approaching” another fish, iii. “Swimming above another” fish) were associated with dominance of feeding. Two other variables (i. Total time occupying the preferred area during the last 2 hours of the 24 h test, ii. Organisms occupying the preferred area when the test ended) were representative of dominance in the place preference test. In all tests, dominant fish compared to subordinate fish displayed a significantly higher number of the behaviours “Rest the head” and “Approaches”. Moreover, dominant sole dominated the sand at the end of the test, and in the group test dominated the area close to the feed delivery point before feed was delivered. The mRNA abundance of the selected mRNAs related to neurogenesis (nrd2) and neuroplasticity (c-fos) in dominant sole compared to subordinate were significantly different. This is the first study to characterise dominance categories with associated behaviours and mRNA abundance in Senegalese sole and provides tools to study dominance related problems in feeding and reproduction in aquaculture. [ABSTRACT FROM AUTHOR]

Based on a social dominance approach, aggression is conceptualized as a strategy used to gain position, power, and influence within the peer network. However, aggression may only be beneficial when targeted against particular peers; both victims' social standing and the number of victims targeted may impact aggressors' social standing. The current study examined associations between aggressors' targeting tendencies (victims' social standing and number of victims) and aggressors' own social standing, both concurrently and over time. Analyses were conducted using three analytic samples of seventh and eighth grade aggressors (Ns ranged from 161 to 383, 49% girls; 50% Latina/o). Participants nominated their friends; nominations were used to calculate social network prestige. Peer nominations were used to identify aggressors and their victim(s). For each aggressor, number of victims and victims' social network prestige were assessed. Aggressors with more victims and with highly prestigious victims had higher social network prestige themselves, and they increased more in prestige over time than aggressors with fewer victims and less prestigious victims (though there were some differences across analytic samples). Findings have implications for the need to extend the social dominance approach to better address the links between aggressors and victims. Aggr. Behav. 43:364-374, 2017. © 2017 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Sexual conflict theory expects females to avoid nonoptimal mating attempts by males. Although female vervet monkeys, Chlorocebus pygerythrus , can resist direct mating attempts, higher-ranking males still have more mating opportunities than lower-ranking ones. We presume that rank-related access reflects male–male competition that may conflict with female reproductive objectives. We extend an earlier report of codominance in this species to show that powerful females can undermine the restrictions imposed through male–male competition by improving the dominance rank of preferred male associates. We found that the dominance hierarchies of the sexes were comprehensively interdigitated and that males who had more female spatial associates, and who groomed with well-connected females, were more likely improve their Elo-ratings, which we use as an index of male power. The effects of partner number and integration, which predicted the probability of the initiation of aggression by lower-ranking males, suggest that association with females offered the prospect of protected threat if this likelihood increased. Although female rank and aggression were not directly consequential for males, we argue that female power and influence are intertwined and that both stem from the strength of female reproductive control. [ABSTRACT FROM AUTHOR]

The concept of social dominance has been used in a plethora of studies to assess animal behaviour and relationships between individuals for nearly a century. Nevertheless, a standard approach does not yet exist to assess dominance in species that have a nonlinear or weakly linear hierarchical structure. We amassed 316 published data sets and show that 73.7% of the data sets and 90.3% of 103 species that we reviewed do not have a strongly linear structure. Herein, we present a novel method, ADAGIO, for assessing the structure of dominance networks. ADAGIO computes dominance hierarchies, in the form of directed acyclic graphs, to represent the dominance relations of a given group of animals. Thus far, most methods for computing dominance ranks assume implicitly that the dominance relation is a total order of the individuals in a group. ADAGIO does not assume or require this to be always true, and is hence more appropriate for analysing dominance hierarchies that are not strongly linear. We evaluated our approach against other frequently used methods, I&SI, David's score and Elo-rating, on 12 000 simulated data sets and on 279 interaction matrices from published, empirical data. The results from the simulated data show that ADAGIO achieves a significantly smaller error, and hence performs better when assigning ranks than other methods. Additionally, ADAGIO generated accurate dominance hierarchies for empirical data sets with a high index of linearity. Hence, our findings suggest that ADAGIO is currently the most reliable method to assess social dominance in gregarious animals living in groups of any size. Furthermore, since ADAGIO was designed to be generic, its applicability has the potential to extend beyond dominance data. The source code of our algorithm and all simulations used for this paper are publicly available at http://ngonga.github.io/adagio/ . [ABSTRACT FROM AUTHOR]

Recent studies have suggested the existence of the emotion of triumph by documenting how its nonverbal signals are displayed and identified across cultures. The current study contributes to this literature by providing additional convergent evidence about the expression of triumph by examining self-reported expressions of triumph from participants from Japan, Russia, Serbia, and the U.S. Self-reported behavioral expressions of triumph were consistent with three factors previously found to be associated with the triumph expression (Expansion, Aggression, Attention), with the exception of a finding on one scale in one country. The Japanese were prone to report greater regulation compared to the experience of triumph, whereas Americans and Serbians reported relatively greater experience compared to regulation. Across countries, Aggression was positively correlated with self-reported experience. The self-reported expressions of triumph partially corresponded with nonverbal reactions that had been identified as triumph in previous research. [ABSTRACT FROM AUTHOR]

Previous studies exploring the link between social status and behavior have predominantly utilized measures that do not provide information regarding toward whom aggression or prosocial behavior is directed. Using a contextualized target-specific approach, this study examined whether high- and low-status adolescents behave differently toward peers of varying levels of status. Participants, aged 11-15 (N = 426, 53 % females), completed measures assessing aggression and prosocial behavior toward each same-sex grademate. A distinct pattern of findings emerged regarding the likeability, popularity, and dominance status of adolescents and their peer targets. Popular adolescents reported more direct aggression, indirect aggression, and prosocial behavior toward popular peers than did unpopular adolescents. Well-accepted adolescents reported more prosocial behavior toward a wider variety of peers than did rejected adolescents. Finally, compared to subordinate adolescents, dominant adolescents reported greater direct and indirect aggression toward dominant than subordinate peers. The results highlight the importance of studying target-specific behavior to better understand the status-behavior link. [ABSTRACT FROM AUTHOR]

The teleost fish nonapeptides, arginine vasotocin (AVT) and isotocin (IT), have been implicated in the regulation of social behavior. These peptides are expected to be involved in acute and transient changes in social context, in order to be efficient in modulating the expression of social behavior according to changes in the social environment. Here we tested the hypothesis that short-term social interactions are related to changes in the level of both nonapeptides across different brain regions. For this purpose we exposed male zebrafish to two types of social interactions: (1) real opponent interactions, from which a Winner and a Loser emerged; and (2) mirror-elicited interactions, that produced individuals that did not experience a change in social status despite expressing similar levels of aggressive behavior to those of participants in real-opponent fights. Non-interacting individuals were used as a reference group. Each social phenotype (i.e. Winners, Losers, Mirror-fighters) presented a specific brain profile of nonapeptides when compared to the reference group. Moreover, the comparison between the different social phenotypes allowed to address the specific aspects of the interaction (e.g. assessment of opponent aggressive behavior vs. self-assessment of expressed aggressive behavior) that are linked with neuropeptide responses. Overall, agonistic interactions seem to be more associated with the changes in brain AVT than IT, which highlights the preferential role of AVT in the regulation of aggressive behavior already described for other species. [ABSTRACT FROM AUTHOR]

The relevance of interpersonal hostile-dominance (HD) to post-discharge aggression in mental health patients is unclear. This study assessed whether (1) HD is stable over time; (2) the relationship between HD and positive, negative, disorganized, and excited symptoms is consistent over time; and (3) HD is related to aggression post-discharge. Two hundred psychiatric inpatients were recruited on admission to hospital; 41 were available for follow-up at 6 months post-discharge, including 29 men and 12 women, with an age range of 19-63 (M = 39.63 years, SD = 12.69 years). Psychiatric symptomatology and interpersonal style were assessed at recruitment and follow-up; aggression in the community post-discharge was measured at follow-up. Results showed that (1) HD was stable over time despite an overall reduction in psychiatric symptoms, (2) HD was positively correlated with symptom severity at both time points, and (3) higher HD, excited symptoms, and positive symptoms measured in the community, and more severe positive symptoms measured in hospital, were associated with aggressive behavior post-discharge. These results suggest that HD is a risk factor for more severe psychopathology. Furthermore, HD, positive symptoms, and excited symptoms measured in the community act as risk factors for aggressive behavior post-discharge. As such, treatment planning and risk assessment should consider HD. Aggr. Behav. 42:324-332, 2016. © 2015 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Peer cliques form an important context for the social development of adolescents. Although clique members are often similar in social status, also within cliques, status differences exist. How differences in social status between clique members are related to behaviors of its individual members is rather unknown. This study examined to what extent the relationship of individual social status (i.e., perceived popularity) with aggression and prosocial behavior depends on the level of internal clique hierarchy. The sample consists of 2674 adolescents (49.8 % boys), with a mean age of 14.02. We focused specifically on physical and relational aggression, and practical and emotional support, because these behaviors have shown to be of great importance for social relationships and social standing among adolescents. The internal status hierarchy of cliques was based on the variation in individual social status between clique members (i.e., clique hierarchization) and the structure of status scores within a clique (pyramid shape, inverted pyramid, or equal distribution of social status scores) (i.e., clique status structure). The results showed that differences in aggressive and prosocial behaviors were particularly moderated by clique status structure: aggression was stronger related to individual social status in (girls') cliques where the clique status structure reflected an inverted pyramid with relatively more high status adolescents within the clique than low status peers, and prosocial behavior showed a significant relationship with individual social status, again predominantly in inverted pyramid structured (boys' and girls') cliques. Furthermore, these effects differed by types of gender cliques: the associations were found in same gender but not mixed-gender cliques. The findings stress the importance of taking into account internal clique characteristics when studying adolescent social status in relationship to aggression and prosociality. [ABSTRACT FROM AUTHOR]

In gregarious animals, social interactions frequently take the form of dominance hierarchies that maintain stable relationships between individuals, and settle disputes without extra costs. Traits that function as signals of status can play an important role in mediating interactions among individuals, both in social and in sexual contexts. Carotenoid ornaments are more generally assumed to be sexually selected and not so relevant to general social contexts. However, it is possible for them to function in social contexts if they signal socially relevant aspects. Here we experimentally analysed social dominance and resource control in male groups of a gregarious species, the European serin, Serinus serinus , in relation to a sexual ornament. We tested whether yellow carotenoid-based plumage coloration, age, body size and testosterone were predictors of social dominance over a nonsexual resource (i.e. feeding context). We showed that dominance hierarchies were steep and were related to testosterone levels and ornamental coloration, particularly the male yellow carotenoid-based crown patch. Our results suggest that carotenoid-based colour and testosterone levels can be reliable predictors of social status in agonistic encounters in groups of male serins. Moreover, together with previous work on the sexual function of male coloration, this study provides evidence that male serin yellow coloration has a dual function in both sexual and nonsexual contexts. These results raise the possibility that this ornament may have evolved and be maintained via social selection over social competition/cooperation for reproductive opportunities and ecological resources. [ABSTRACT FROM AUTHOR]

In social mammals, the position of a male in the group’s hierarchy strongly affects his reproductive success. Since a high social rank is often gained through competition with other males, selection should favour bigger males over smaller ones. We may therefore predict faster growth and/or delayed sexual maturity in dominant males. Likewise, dominants should have higher levels of testosterone, hormone important in many aspects of male dominance. Less obvious is the relationship between dominance and levels of corticosterone but generally higher concentrations are expected in subordinate individuals. We studied body growth, sexual maturation and endocrinal changes in males of two house mouse subspecies, raised in fraternal pairs. Since Mus musculus domesticus is the subspecies which dominates mutual encounters with Mus musculus musculus we predicted higher growth rate, delayed puberty and aggression, and higher testosterone and corticosterone levels in domesticus males compared to musculus . In all comparisons, no differences were found between dominant and subordinate musculus brothers. On the other hand, in M. m. domesticus , dominant males revealed a different growth trajectory and lower corticosterone levels than subordinate males but not delayed puberty and higher testosterone concentrations, thus contradicting our predictions. In inter-subspecific comparisons, musculus males matured earlier but became aggressive at the same time as domesticus males. The musculus testosterone ontogeny suggests that social positions in this subspecies remain unfixed for an extended period and that the increasing levels probably reflect prolonged hierarchy contests. It appears that the ontogeny of behaviour and physiological traits diverge cryptically between the two subspecies. [ABSTRACT FROM AUTHOR]

Previous studies have documented the correlation between preferences for male facial masculinity and perceived masculinity: women who rate their male partner as more masculine tend to prefer more masculine faces. Men's self-rated masculinity predicts their female partner's preference for masculinity. This study examined the association between other trait preferences and preference for male facial masculinity among 556 gay and bisexual men across multiple cities in China. Participants were asked to choose the three most important traits in a romantic partner from a list of 23 traits. Each participant was then asked to choose a preferred face in each of 10 pairs of male faces presented sequentially, with each pair consisting of a masculinized and feminized version of the same base face. The results indicated that preferences for health and status-related traits were correlated with preferences for male facial masculinity in gay and bisexual men in China; individuals who were more health- or status-oriented in their preferences for a romantic partner preferred more masculine male faces than individuals with lower levels of these orientations. The findings have implications for the correlated preferences for facial masculinity and health- and status-related traits and may be related to perceived health and dominance/aggression of masculine faces based on a sample of non-Western gay and bisexual men. [ABSTRACT FROM AUTHOR]

Animals of different social status exhibit variation in aggression, territorial and reproductive behavior as well as activity patterns, feeding, drinking and status signaling. This behavioral and physiological plasticity is coordinated by underlying changes in brain gene transcription. Using Tag-based RNA sequencing (Tag-seq), we explore RNA transcriptomes from the medial preoptic area (mPOA) and ventral hypothalamus (vHYP) of male mice of different social ranks in a dominance hierarchy and detect candidate genes and cellular pathways that underlie status-related plasticity. Within the mPOA, oxytocin (Oxt) and vasopressin (Avp) are more highly expressed in subdominant mice compared to other ranks, while nitric oxide synthase (Nos1) has lower expression in subdominant mice. Within the vHYP, we find that both orexigenic and anorexigenic genes involved in feeding behavior, including agouti-related peptide (Agrp), neuropeptide-Y (Npy), galanin (Gal), proopiomelanocortin (Pomc), and Cocaine- and Amphetamine-Regulated Transcript Protein prepropeptide (Cartp t), are less expressed in dominant animals compared to more subordinate ranks. We suggest that this may represent a reshaping of feeding circuits in dominant compared to subdominant and subordinate animals. Furthermore, we determine several genes that are positively and negatively associated with the level of despotism (aggression) in dominant males. Ultimately, we identify hypothalamic genes controlling feeding and social behaviors that are differentially transcribed across animals of varying social status. These changes in brain transcriptomics likely support phenotypic variation that enable animals to adapt to their current social status. • Behavioral and physiological plasticity underlies acquisition of social status. • Tag-based RNA-seq reveals differential brain gene expression by social status. • Oxytocin and vasopressin gene expression in the mPOA is higher in sub-dominant compared to dominant males. • Feeding-behavior genes in ventral hypothalamus have lower expression in dominant mice. • WGCNA and GO analysis shows cellular pathways and signaling cascades vary by status. [ABSTRACT FROM AUTHOR]

Social carnivores have been central in studies of cooperative breeding, and research using noninvasive methods to examine behavioral and endocrine mechanisms of reproductive suppression started in the 1980s with dwarf mongooses in Serengeti National Park. Here, I synthesize the methods, findings and limitations of a research program that examined relationships between social dominance, age, mass, aggression, mating, gonadal steroids, glucocorticoids and reproduction in female and male dwarf mongooses, African wild dogs and wolves. Infanticide is a reliable backstop for reproductive suppression in females, and reproduction is energetically costly in these species. These conditions favor hypothalamic – pituitary – gonadal (HPG) adaptations that reduce the fertility of subordinate females to avoid the cost of producing doomed offspring. Infanticide also favors close synchronization of reproduction when subordinate females do become pregnant. In males, infanticide is a less reliable backstop and reproduction is less costly, so direct effects of subordination on fertility are less pronounced. Age is a strong predictor of social dominance in these species, but the evolutionary reason for this is not clear. In dwarf mongooses and wild dogs, alpha females were never deposed by younger packmates, but alpha males were: this difference is also not understood. Patterns of reproduction supported models predicting that alphas are less likely to share reproduction when the fitness costs of reproduction are high, when the fitness expected for dispersers is low, and with young subordinates to whom they are more closely related. Correlations between dominance and adrenal glucocorticoid concentrations varied between species and sexes, but did not support the hypothesis that chronic stress causes reproductive suppression. • In many social carnivores, subordinates do not breed. • Inhibition of ovarian steroid secretion (directly or indirectly) often mediates reproductive suppression in females • Reproductive suppression of males is more often mediated by behavior than by hypothalamic – pituitary – gonadal function • Reproductive suppression is usually not mediated by glucocorticoids • Infanticide underlies many of the differences between females and males [ABSTRACT FROM AUTHOR]

Social subordination increases risk for psychiatric disorders, while dominance increases resilience to these disorders. Fluoxetine, a selective serotonin (5HT) reuptake inhibitor whose actions are mediated in part by the 5HT1A receptor (5HT1AR), has sex- and social status-specific effects on socioemotional behavior and aggressive behavior. However, the impact of social status on these sex-specific effects remains unclear. The current study evaluated the impact of acute fluoxetine treatment and social status on dominance-related behaviors in female and male hamsters, and the impact of chronic fluoxetine treatment on socioemotional behavior and 5HT1AR binding potential (5HT1AR BP) in female rhesus macaques. We hypothesized that sex differences in the effects of fluoxetine on aggression in hamsters would be diminished in dominant and enhanced in subordinate males and that aggression in female hamsters would be enhanced in dominants and diminished in subordinates. In female rhesus macaques, we hypothesized that chronic fluoxetine would alter socioemotional behaviors and site-specific 5HT1AR BP in a status-dependent manner. Male (n = 46) and female (n = 56) hamsters were paired with conspecifics for three days to establish social rank. Hamsters received a single dose of 20 mg/kg fluoxetine or vehicle two-hours prior to a test with a non-aggressive intruder. Female rhesus monkeys (n = 14) housed were administered fluoxetine (2.8 mg/kg/day) or vehicle injections chronically for 14-days, separated by a three-week washout period. On Day 15, positron emission tomography neuroimaging for 5HT1AR BP was conducted. Fluoxetine treatment decreased aggression in subordinate female monkeys and subordinate female hamsters but not in dominant females of either species. Fluoxetine decreased aggression in dominant but not in subordinate male hamsters. Fluoxetine also reduced and increased prefrontal 5HT1AR BP in dominant and subordinate females, respectively. Taken together, these results provide cross-species evidence that social status and sex impact how increased 5HT modulates agonistic behavior. • Fluoxetine decreased aggression in subordinate female hamsters and monkeys. • Fluoxetine did not impact aggression in dominant females of either species. • Fluoxetine decreased aggression in dominant but not in subordinate male hamsters. • Fluoxetine had opposite effects on prefrontal 5HT1AR in dominant and subordinate female monkeys. • Social status and sex impact how 5HT modulates agonistic behavior across species. [ABSTRACT FROM AUTHOR]

Behavioural syndrome literature suggests that behavioural traits may be coupled to form behavioural strategies that are consistent and repeatable across contexts. Typically these behavioural types are composed of bold, aggressive, dominant individuals and shy, less aggressive, subordinate individuals. Mountain chickadees living in varying climatic conditions across a montane environment appear to exhibit consistent behavioural types, such that high elevation birds, which experience harsher winter conditions and rely more heavily on spatial memory to retrieve food caches to survive winter, explore a novel environment at a slower rate (i.e., shy) and are socially subordinate to low elevation birds. Dominance is typically expressed in individual pairwise interactions, but it is not always clear which traits predispose an individual to become a dominant in such interactions. Aggression is frequently suggested to be associated with higher dominance status, yet the data are equivocal. Here we aimed to test whether previously described elevation related differences in social dominance might be associated with elevation related differences in aggression levels in mountain chickadees by using the mirror test. The mirror test can address potential differences in reactive and proactive aggression, although caution should be taken when using the mirror test as some species are able to self-recognize. Low elevation birds responded more aggressively to their mirror image than high elevation birds, suggesting that elevation related differences in aggression may be partially responsible for previously found differences in social dominance status. [ABSTRACT FROM AUTHOR]

The article discusses bullying as a means to become socially dominant during the childhood years. Topics covered include the implications of power and social hierarchy for bullying and the prevalence of such action in the workplace and at schools. Also mentioned are the cultural expectations for those who have been bullied.

Neuropeptides modulate many aspects of behavior and physiology in a broad range of animals. Arginine vasotocin (AVT) is implicated in mediating social behavior in teleost fish, although its specific role varies between species, sexes, life stages, and social context. To investigate whether the effects of AVT on behavior depend on social context, we used the African cichlid fish Astatotilapia burtoni , which is well-known for its remarkable behavioral plasticity. We pharmacologically manipulated the AVT system in established socially dominant and subordinate A. burtoni males, as well as in males ascending to dominance status in a socially unstable environment. Our results show that exogenous AVT causes a stress response, as evidenced by reduced behavioral activity and increased circulating levels of cortisol in established dominant and subordinate males. Administration of the AVT antagonist Manning compound, on the other hand, did not affect established subordinate or dominant males. However, AVT antagonist-treated males ascending from subordinate to dominant status exhibited reduced aggressive and increased courtship behavior compared to vehicle-treated animals. Finally, we measured circulating cortisol levels and brain gene expression levels of AVT and its behaviorally relevant V1a2 receptor in all three social phenotypes and found that plasma cortisol and mRNA levels of both genes were increased in ascending males compared to dominant and subordinate males. Our results provide a more detailed understanding of the role of the AVT system in the regulation of complex behavior in a dynamically changing social environment. [ABSTRACT FROM AUTHOR]

Depression is one of the most common chronic mental disorders, which is a leading cause of morbidity and mortality in patients. Depression often leads to offensive and defensive behaviours but the underlying mechanisms are not known. We propose that the aggressive behaviours in depression can be modelled in animal experiments. In this study, we successfully established a mouse model of depression using the chronic unpredictable mild stress (CUMS) paradigm and detected aggressive and social dominance behaviours in rodents by resident/intruder test and social dominance tube test (SDTT), respectively. The CUMS-exposed mice showed increased defensive, offensive and aggressive behaviours in the resident-intruder test. In the SDTT, these mice showed enhanced social dominance. These alterations were associated with reduced MAP-2 expression in the hippocampus while no difference in β-tubulin expression was detected. In addition, the treatment of anti-depressant fluoxetine reversed the aggressive behaviours without reducing the social dominance behaviour induced by CUMS. However, fluoxetine did effectively reverted the changes in MAP-2 expression in the hippocampus. In addition, the nonspecific tricyclic antipsychotic drug, clozapine, reversed all symptoms of CUMS-exposed mice including aggressive tendencies, impulsive violence, social dominance behaviour and MAP-2 expression in the hippocampus. The results suggests that social maladjustment such as competition and social dominance are likely related to the dopaminergic system rather than the serotonergic system and the hippocampal dendritic structure protein MAP-2. Thus, dominance can be separated from aggression. This study shows that aggression/hostility and social hierarchy/dominance are increased in the CUMS-exposed mice and thus provide an excellent model for further study in the diagnosis and the treatment of depression-associated aggression. [ABSTRACT FROM AUTHOR]