Acquisition of cocaine reinforcement using fixed-ratio and concurrent choice schedules in socially housed female and male monkeys

RATIONALE

Previous studies in socially housed monkeys examining acquisition of cocaine self-administration under fixed-ratio (FR) schedules of reinforcement found that subordinate males and dominant females were more vulnerable than their counterparts.

OBJECTIVES

The present studies extended these findings in two ways: (1) to replicate the earlier study, in which female monkeys were studied after a relatively short period of social housing (~ 3 months) using cocaine-naïve female monkeys (n = 9; 4 dominant and 5 subordinate) living in well-established social groups (~ 18 months); and (2) in male monkeys (n = 3/social rank), we studied cocaine acquisition under a concurrent schedule, with an alternative, non-drug reinforcer available.

RESULTS

In contrast to earlier findings, subordinate female monkeys acquired cocaine reinforcement (i.e., > saline reinforcement) at significantly lower cocaine doses compared with dominant monkeys. In the socially housed males, no dominant monkey acquired a cocaine preference (i.e., > 80% cocaine choice) over food, while two of three subordinate monkeys acquired cocaine reinforcement. In monkeys that did not acquire, the conditions were changed to an FR schedule with only cocaine available and after acquisition, returned to the concurrent schedule. In all monkeys, high doses of cocaine were chosen over food reinforcement.

CONCLUSIONS

The behavioral data in females suggests that duration of social enrichment and stress can differentially impact vulnerability to cocaine reinforcement. The findings in socially housed male monkeys, using concurrent food vs. cocaine choice schedules of reinforcement, confirmed earlier social-rank differences using an FR schedule and showed that vulnerability could be modified by exposure to cocaine.

Effects of temperament during handling and social rank on the blood biochemical parameters of common eland (Taurotragus oryx)

Large herbivores are subject to handling and social stress in captivity. These may affect blood biochemical values, which motivated this research. Twelve healthy common eland (Taurotragus oryx) were monitored for 12 months. The animals were handled monthly, and blood samples were collected. Samples from every second month were analysed for 14 blood biochemical parameters. Temperament throughout the handling, as the summation of various behavioural responses, was calculated as a proxy of the stress generated during handling. Social behaviour was recorded each month, and the agonistic interactions were used to calculate the social rank, which was considered a proxy of social stress. Generalised Linear Mixed Models were designed to test the effects of temperament and social rank on the blood biochemical parameters while keeping sex, age, body condition, and body weight as covariates. The results show that the temperament during handling influences blood levels of albumin, alkaline phosphate, blood urea nitrogen, glucose, total bilirubin, and total protein; however, social rank has little influence, affecting just albumin. The ranges observed in the values of these biochemical parameters were still within their reference intervals, implying the absence of pathology or physiological problems during the study. The results suggest that blood biochemical values of physically restrained common eland should be carefully interpreted, even in animals already habituated to routine handling. On the contrary, social rank has low effects on the blood biochemical parameters.

Characterization of social hierarchy formation and maintenance in same-sex, group-housed male and female C57BL/6 J mice

Social hierarchies are a prevalent feature of all animal groups, and an individual's rank within the group can significantly affect their overall health, typically at the greatest expense of the lowest-ranked individuals, or omegas. These subjects have been shown to exhibit various stress-related phenotypes, such as increased hypothalamic-pituitary axis activity and increased amygdalar corticotropin-releasing factor levels compared to higher-ranked subjects. However, these findings have been primarily characterized in males and in models requiring exhibition of severe aggression. The goals of the current study, therefore, were to characterize the formation and maintenance of social hierarchies using the tube test and palatable liquid competition in same-sex groups of male and female C57BL/6 J mice. We also aimed to examine the effects of tube test-determined social rank on plasma and hypothalamic oxytocin and vasopressin levels, peptides with established roles in social behaviors and the stress response. Lastly, we assessed the effects of environmental enrichment and length of testing on the measures outlined above. Overall, we demonstrated that males and females develop social hierarchies and that these hierarchies can be determined using the tube test. While we were unable to establish a consistent connection between peptide levels and social rank, we observed transient changes in these peptides reflecting complex interactions between social rank, sex, environment, and length of testing. We also found that many male and female omegas began to exhibit passive coping behavior after repeated tube test losses, demonstrating the potential of this assay to serve as a model of chronic, mild psychosocial stress.

Dating app usage and motivations for dating app usage are associated with increased disordered eating

The centrality of physical appearance in dating app environments may constitute an appearance-related pressure that increases the likelihood of body dissatisfaction (BD) and disordered eating (DE), thus exacerbating the relationship between DE-predictive traits and DE itself. Although dating app use has been linked to BD and DE, prior research has also neglected the role of individuals' dating app use motivations and relevant traits in eating pathology. To address these gaps, the current study investigated whether dating app usage moderated the effects of appearance-based rejection sensitivity, fear of negative evaluation, emotion dysregulation, and perceived social rank on DE. We also examined the unique effects of individuals' dating app use motivations on DE. Participants (N = 690) completed baseline measures of demographic and trait variables including dating app usage. DE was positively associated with female gender, higher body mass index, a history of eating disorder (ED) diagnosis, appearance-based rejection sensitivity, and emotion dysregulation. There was a small, positive association between dating app usage and DE, indicating that dating app users were more likely to report DE symptoms, appearance-based rejection sensitivity, and emotion dysregulation. No investigated predictor was moderated by dating app usage, but four of the six measured motivations for using dating apps (love, self-worth, ease of communication, and thrill of excitement motivations) were associated with DE among the dating app user sample (casual sex and trendiness motivations were not). Given that DE behaviours can lead to EDs, the present findings suggest that lifetime dating app usage may increase socio-cultural appearance pressures that confer risk for DE.

Variation in inhibitory control does not influence social rank, foraging efficiency, or risk taking, in red junglefowl females

Individual variation in cognition, seen in many taxa, is not well understood, despite its potential evolutionary consequences. Inhibitory control is an aspect of cognition which differs between individuals. However, how selection could act on this variation remains unclear. First, individual consistency over time of behaviours affected by inhibitory control, and how these behaviours relate to each other, is not well understood. Second, consequences in ecologically relevant contexts of variation in behaviours affected by  inhibitory control, are scarcely investigated. Therefore, we explored the temporal consistency and inter-relatedness of two behaviours influenced by inhibitory control (impulsive action and persistence) and how these link to social rank, foraging efficiency, and risk taking in adult female red junglefowl (Gallus gallus). We measured impulsive action in a detour test, and persistence in both a detour test and a foraging test. Impulsive action and persistence, measured in a detour test, were moderately consistent over time, and positively correlated. This implies that selection could act on inhibitory control via these behaviours, and selection on one behaviour could affect the other. However, we found no evidence of links between inhibitory control and social rank, foraging efficiency, or risk taking. This implies that selection may not act on inhibitory control via these measures, and that, in general, there may be a lack of strong selection on inhibitory control. This, in turn, could help explain individual variation in this aspect of cognition. Future research should explore the specificity of when inhibitory control has implications for individuals, and continue to investigate how variation in cognitive traits influences how individuals behave in contexts with potential evolutionary implications.

Repeatability of endocrine traits and dominance rank in female guinea pigs

BACKGROUND

Glucocorticoids (e.g. cortisol) are associated with variation in social behavior, and previous studies have linked baseline as well as challenge-induced glucocorticoid concentrations to dominance status. It is known that cortisol response to an acute challenge is repeatable and correlates to social behavior in males of many mammal species. However, it is unclear whether these patterns are also consistent for females. The aim of this study was to investigate whether baseline and response cortisol concentrations are repeatable in female guinea pigs (Cavia aperea f. porcellus) and whether dominance rank is stable and correlated to baseline cortisol concentration and/or cortisol responsiveness.

RESULTS

Our results show that cortisol responsiveness (after 1 h: R = 0.635, 95% CI = 0.229, 0.927; after 2 h: R = 0.764, 95% CI = 0.433, 0.951) and dominance rank (R = 0.709, 95% CI = 0.316, 0.935) of females were significantly repeatable after six weeks but not correlated. Baseline cortisol was not repeatable (R = 0, 95% CI = 0, 0.690) and also did not correlate to dominance rank. Furthermore, the difference in repeatability estimates of baseline and response values was due to high within-individual variance of baseline cortisol concentration; the amount of between-individual variance was similar for baseline cortisol and the two measures of cortisol responsiveness.

CONCLUSIONS

Females occupying different dominance ranks did not have long-term differences in cortisol concentrations, and cortisol responsiveness does not seem to be significantly involved in the maintenance of dominance rank. Overall, this study reveals the remarkable stability of cortisol responsiveness and dominance rank in a female rodent, and it remains an open question whether the magnitude of cortisol responsiveness is adaptive in social contexts for females.

The Influence of Negative Feedback and Social Rank on Feelings of Shame and Guilt: A Vignette Study in 8- to 13-Year-Old Non-Clinical Children

This experimental study examined the role of negative feedback and social rank in the experience of self-conscious emotions, shame and guilt, in typically developing children aged 8 to 13 years. Participants were tested by means of a vignette paradigm in which feedback and social rank were systematically manipulated and levels of shame and guilt were assessed after listening to each of the vignettes. In addition, children completed a set of questionnaires for measuring individual differences in shame and guilt proneness, social comparison, submissive behavior, and external shame. The results showed that children presented with negative feedback reported higher ratings of shame and guilt than when presented with positive feedback, implying that the provision of negative feedback has a significant impact on children's experience of self-conscious emotions. Social rank had less effect on children's report of these self-conscious emotions. Furthermore, the individual difference variables of guilt proneness, and to a lesser extent shame proneness and submissive behavior, appeared to be positively related to self-conscious emotions as reported during the vignette task.

Double trouble: Prenatal immune activation in stress sensitive offspring

Viral infections during pregnancy are associated with increased incidence of psychiatric disorders in offspring. The pathological outcomes of viral infection appear to be caused by the deleterious effects of innate immune response-associated factors on development of the fetus, which predispose the offspring to pathological conditions in adulthood. The negative impact of viral infections varies substantially between pregnancies. Here, we explored whether differential stress sensitivity underlies the high heterogeneity of immune reactivity and whether this may influence the pathological consequences of maternal immune activation. Using mouse models of social dominance (Dom) and submissiveness (Sub), which possess innate features of stress resilience and vulnerability, respectively, we identified differential immune reactivity to the synthetic analogue of viral double-stranded RNA, Poly(I:C), in Sub and Dom nulliparous and pregnant females. More specifically, we found that Sub females showed an exacerbated pro- and anti-inflammatory cytokine response to Poly(I:C) as compared with Dom females. Sub offspring born to Sub mothers (stress sensitive offspring) showed enhanced locomotory response to the non-competitive NMDA antagonist, MK-801, which was potentiated by prenatal Poly(I:C) exposure. Our findings suggest that inherited stress sensitivity may lead to functional changes in glutamatergic signaling, which in turn is further exacerbated by prenatal exposure to viral-like infection. The maternal immunome seems to play a crucial role in these observed phenomena.

Gonadotropin-inhibitory hormone as a regulator of social interactions in vertebrates

The social environment changes circulating hormone levels and expression of social behavior in animals. Social information is perceived by sensory systems, leading to cellular and molecular changes through neural processes. Peripheral reproductive hormone levels are regulated by activity in the hypothalamic-pituitary-gonadal (HPG) axis. Until the end of the last century, the neurochemical systems that convey social information to the HPG axis were not well understood. Gonadotropin-inhibitory hormone (GnIH) was the first hypothalamic neuropeptide shown to inhibit gonadotropin release, in 2000. GnIH is now regarded as a negative upstream regulator of the HPG axis, and it is becoming increasingly evident that it responds to social cues. In addition to controlling reproductive physiology, GnIH seems to modulate the reproductive behavior of animals. Here, we review studies investigating how GnIH neurons respond to social information and describe the mechanisms through which GnIH regulates social behavior.

Antioxidant capacity differs across social ranks and with ascension in males of a group-living fish

Animals that live in groups often form hierarchies in which an individual's behaviour and physiology varies based on their social rank. Occasionally, a subordinate can ascend into a dominant position and the ascending individual must make rapid behavioural and physiological adjustments to solidify their dominance. These periods of social transition and instability can be stressful and ascending individuals often incur large metabolic costs that could influence their oxidative status. Most previous investigations examining the link between oxidative status and the social environment have done so under stable social conditions and have evaluated oxidative status in a single tissue. Therefore, evaluations of how oxidative status is regulated across multiple tissues during periods of social flux would greatly enhance our understanding of the relationship between oxidative status and the social environment. Here, we assessed how antioxidant capacity in three tissues (brain, gonad, and muscle) varied among dominant, subordinate, and ascending males of the group-living cichlid fish, Neolamprologus pulcher. Antioxidant capacity in the brain and muscle of ascending males was intermediate to that of dominant (highest levels) and subordinate males (lowest levels) and correlated with differences in social and locomotor behaviours, respectively. Gonad antioxidant capacity was lower in ascending males than in dominant males. However, gonad antioxidant capacity was positively correlated with the size of ascending males' gonads suggesting that ascending males may increase gonad antioxidant capacity as they develop their gonads. Overall, our results highlight the widespread physiological consequences of social ascension and emphasize the importance of tissue-specific measures of oxidative status.

The fragility of perceived social rank following exercise in anorexia nervosa: an ecological momentary assessment study of shame and pride

PURPOSE

Pride and shame are self-conscious emotions closely associated with perceived social rank. Goss and Gilbert (In: Gilbert and Miles (eds) Body shame: conceptualization, research & treatment. Brunner-Routledge, Hove, 2002) proposed that weight-control behaviours in anorexia nervosa (AN) provide a temporary sense of increased rank that dissipates afterwards, thereby perpetuating further symptoms. This pilot study tested their theory by examining whether shame increases and pride decreases as time passes post-exercise in individuals with AN. Pre-exercise patterns were also explored.

METHODS

Over 2 weeks, 23 females with AN provided ecological momentary assessment data via six semi-random daily signals and after each exercise episode. The State Shame and Guilt Scale assessed pride and shame. Items modified from the Experience of Shame Scale and the Other as Shame Scale assessed general shame and body/eating shame. Multilevel models analyzed patterns of shame and pride prior to and following exercise episodes.

RESULTS

In the hours after exercise, pride decreased, body/eating shame increased, and general shame increased on one measure. Pride was, therefore, higher and shame lower immediately after exercise as compared to later in the day. In the hours before exercise, pride increased, but shame levels did not change significantly.

CONCLUSION

The anticipation and immediate aftermath of exercise may be associated with higher perceived social rank in people with AN, but their feelings about self may worsen as time passes after exercise. Fluctuations in shame and pride may contribute to the maintenance of exercise in people with AN.

LEVEL OF EVIDENCE

IV, multiple time series analysis.

Degree of influence in class modifies the association between social network diversity and well-being: Results from a large population-based study in Japan

BACKGROUND

Social network diversity can be associated with physical and mental health among adolescents, which might be modified by their perceived degree of influence in class. We aimed to examine the association between social network diversity and physical and mental health, and to elucidate its effect modification by perceived degree of influence in class.

METHODS

Data were obtained from the Kochi Child Health Impact of Living Difficulty (K-CHILD) study in 2016, which targeted 5th, 8th and 11th grade children living in Kochi Prefecture in Japan (N = 9998). Social network diversity accounted for the number of social roles in which adolescents had regular contact. Degree of influence in class, depression (using Depression Self-Rating Scale for children (DSRS)) and self-rated health were assessed by children, and behavior problem and prosocial behavior (using Strengths and Difficulties Questionnaire (SDQ)) was assessed by caregivers.

RESULTS

Significant association of social network diversity with depression (Coefficient (B) = -0.59, 95% confidence interval (CI) = -0.68 to -0.50), self-rated health (B = 0.09, 95% CI = 0.07 to 0.11), behavior problem (B = -0.71, 95% CI = -0.82 to -0.61) and prosocial behavior (B = 0.06, 95% CI = 0.02 to 0.11) were found. The association with depression and self-rated health was stronger among children with perceived low degree of influence (both p for interaction < 0.001). A similar trend was observed for behavior problem (p for interaction = 0.053), but effect modification was not found for the association between social network diversity and prosocial behavior.

CONCLUSIONS

Social network diversity was beneficial for adolescent physical and mental health, especially for children with perceived lower degree of influence in class.

Atypically High Reproductive Skew in a Small Wild Chimpanzee Community in a Human-Dominated Landscape

Social rank is positively correlated with reproductive success in numerous species, albeit demographic factors often influence those patterns. In multimale primate species, reproductive skew tends to decrease with increasing numbers of males and sexually receptive females. Alpha male chimpanzees (Pan troglodytes) often sire a disproportionate, though somewhat variable, percentage of offspring compared to other males. In a small community of eastern chimpanzees inhabiting a human-dominated landscape in Bulindi, Uganda, we found extraordinarily high levels of alpha male reproductive success over a 5-year period (7/8 offspring = 88%), despite the presence of multiple subordinate males. The skew exceeds that reported in other studies of chimpanzees as well as closely related bonobos (Pan paniscus). Our findings underscore the role of demographic and social factors in male reproductive success and also suggest that conclusions about species differences may be premature. The interaction of small community size, dispersal limitations, and male reproductive strategies like those found here may decrease genetic diversity and increase the risk of concomitant inbreeding in chimpanzee communities under strong anthropogenic pressure.

The stress of being alone: Removal from the colony, but not social subordination, increases fecal cortisol metabolite levels in eusocial naked mole-rats

In many social species, hierarchical status within the group is associated with differences in basal adrenocortical activity. We examined this relationship in naked mole-rats (Heterocephalus glaber), eusocial rodents with arguably the most extreme social hierarchies of all mammals. This species lives in colonies where breeding is restricted to one socially dominant 'queen' and her male consorts, and all other individuals are reproductively suppressed 'subordinates'. The relationship between cortisol and social status in naked mole-rats has not fully been elucidated, as prior results on this topic have been contradictory. We used non-invasive feces sampling to measure baseline cortisol levels in eight laboratory colonies of naked mole-rats, to either replicate or reject rank differences. First, we successfully validated an assay to measure fecal cortisol metabolites (FCMs). Removal from the colony for the validation experiment, either alone or with an opposite sex conspecific, induced prolonged elevation of FCM levels on a scale of days to weeks. This increase in cortisol did not prevent the removed animals from sexually maturing. In colony-housed animals, we found no relationship between rank in the social hierarchy and FCM levels. Further, queens, breeding males, and reproductively suppressed subordinates all had equivalent FCM levels. We conclude that this species shows little evidence of the 'stress of dominance' or 'stress of subordination' and that reproductive suppression in naked mole-rats is not driven by elevated cortisol levels.

How dominance hierarchies emerge from conflict: A game theoretic model and experimental evidence

We develop a game theoretic model of conflict and empirically test its predictions to study the emergence of social hierarchies in small groups. Previous research shows uncertainty about actors' ability may lead to more conflict; conflict demonstrates actors' ability and establishes relationships of dominance and submissiveness. Since we assume uncertainty regarding ability to be a crucial cause of conflict, we focus on the effects of different information conditions. We posit that actors know the distribution of abilities in their group and vary whether or not they know (1) their own ability and (2) their interaction partners' interaction histories. Our results from a laboratory experiment closely match qualitative model predictions. Most importantly, conflict produces information about actors' ability, which reduces subsequent conflict. In an exploratory analysis we investigate to what extent gender, social value orientation, risk preferences and a competitive personality account for the quantitative discrepancies between model predictions and subject behavior.

Social anxiety and sensitivity to social-rank features in male faces

BACKGROUND AND OBJECTIVES

Evolutionary theories propose that socially anxious individuals are especially sensitive to social-rank signals, presumably at the expense of the attunement to signals of affiliation. Despite this theoretical claim, few empirical attempts examined the association between social anxiety (SA) and sensitivity to specific features of social-rank and affiliation. This study aims to fill this gap.

METHOD

Participants (N = 67) completed two tasks in which two emotionally neutral computer-generated male faces of the same character were presented side-by-side. In the Social-Rank-Sensitivity Task, the faces within each pair differed in their level of dominance and, in the Affiliation-Sensitivity Task, the faces differed in their level of trustworthiness. The participants' task was to decide which of the two faces looked more dominant or friendly.

RESULTS

There were no differences in accuracy between high- and low-SA participants in the Affiliation-Sensitivity Task. In contrast, high-SA participants were more accurate than low-SA participants in the Social-Rank-Sensitivity Task. No group differences were found in decision latencies in either task.

LIMITATIONS

Limitations of the study are that a non-clinical sample was used and that only computer-generated male faces were considered.

CONCLUSIONS

Our findings suggest that SA is related to an enhanced ability to discriminate faces based on social-rank features. Examining sensitivity to facial cues signaling social-rank and affiliation may help to specify the nature of social threat sensitivity in SA.

Role of social behaviour in the epidemiology of lobomycosis-like disease (LLD) in estuarine common bottlenose dolphins from Ecuador

Lobomycosis-like disease (LLD) is a chronic granulomatous skin disorder that affects Delphinidae worldwide. LLD has been observed in common bottlenose dolphins Tursiops truncatus from the Gulf of Guayaquil, Ecuador, since 1990. Although exogenous factors such as salinity and pollution may play a role in the pathogenesis of this disease in estuarine and coastal dolphin communities, we hypothesized that demography and social behaviour may also influence its epidemiology. To address this issue, the role of social behaviour in the distribution and prevalence of LLD was assessed through hierarchical cluster analysis and spatial distribution analysis in 7 dolphin communities inhabiting the inner estuary. Individuals with LLD lesions were observed in 5 of the 7 dolphin communities, with 13 of the 163 (8%) animals being positive, all adults. Among 8 dolphins of known sex, LLD affected mostly males (86%), who usually were found in pairs. Prevalence was low to moderate (5.1-13%) in dolphin communities where low-rank males had LLD. Conversely, it was high (44.4%, n = 9) in a small community where a high-rank male was infected. LLD affected both dolphins in 2 of the 4 male pairs for which large time series data were available, suggesting horizontal transmission due to contact. Thus, association with LLD-positive males seems to be an important risk factor for infections. Additionally, low-rank males had larger home ranges than high-rank males, indicating that low-status LLD-affected dolphins are likely responsible for the geographic dissemination of the disease in this population.

The relationship between social rank and spatial learning in pheasants, Phasianus colchicus: cause or consequence?

Individual differences in performances on cognitive tasks have been found to differ according to social rank across multiple species. However, it is not clear whether an individual’s cognitive performance is flexible and the result of their current social rank, modulated by social interactions (social state dependent hypothesis), or if it is determined prior to the formation of the social hierarchy and indeed influences an individual’s rank (prior attributes hypothesis). We separated these two hypotheses by measuring learning performance of male pheasants, Phasianus colchicus, on a spatial discrimination task as chicks and again as adults. We inferred adult male social rank from observing agonistic interactions while housed in captive multi-male multi-female groups. Learning performance of adult males was assayed after social rank had been standardised; by housing single males with two or four females. We predicted that if cognitive abilities determine social rank formation we would observe: consistency between chick and adult performances on the cognitive task and chick performance would predict adult social rank. We found that learning performances were consistent from chicks to adults for task accuracy, but not for speed of learning and chick learning performances were not related to adult social rank. Therefore, we could not support the prior attributes hypothesis of cognitive abilities aiding social rank formation. Instead, we found that individual differences in learning performances of adults were predicted by the number of females a male was housed with; males housed with four females had higher levels of learning performance than males housed with two females; and their most recent recording of captive social rank, even though learning performance was assayed while males were in a standardized, non-competitive environment. This does not support the hypothesis that direct social pressures are causing the inter-individual variation in learning performances that we observe. Instead, our results suggest that there may be carry-over effects of aggressive social interactions on learning performance. Consequently, whether early life spatial learning performances influence social rank is unclear but these performances are modulated by the current social environment and a male’s most recent social rank.

Stress axis regulation during social ascension in a group-living cichlid fish

Animals living in groups often form social hierarchies, with characteristic behaviours and physiologies associated with rank. However, when social opportunities arise and a subordinate ascends into a dominant position, quick adjustments are necessary to secure this position. Such periods of social transition are typically associated with elevated glucocorticoid production, but the precise regulation of the stress axis during these occasions is not well understood. Using the group-living cichlid, Neolamprologus pulcher, the effects of social ascension on the stress axis were assessed. Ascenders rapidly filled experimentally created vacancies, adopting a dominant behavioural phenotype within 72 h-elevating aggression, activity, and workload, while receiving high rates of affiliative behaviours from their group members. Despite assuming behavioural dominance within their groups, ascenders displayed higher cortisol levels than dominants three days post-ascension. Additionally, compared to subordinates, ascenders had increased transcript abundance of steroidogenic acute regulatory protein (star) and cytochrome p450 side-chain cleavage enzyme (p450scc) in the head kidney, indicating activation of the stress axis. Cortisol levels were lowest in ascenders that displayed low rates of aggression, potentially reflecting the reestablishment of social stability in these groups. Increased transcript abundance of both glucocorticoid receptors (gr1 and gr2) in the brain's preoptic area (POA) of ascenders compared to dominants suggested an enhanced capacity for cortisol regulation via negative feedback. Our results reveal a regulatory cascade of behavioural and physiological interactions and highlight the importance of investigating the underlying mechanisms regulating the stress axis.

Out of my league: Appraisals of anxiety and confidence in others by individuals with and without social anxiety disorder

Forty participants with social anxiety disorder (SAD) and 42 healthy controls (HCs) were randomized to watch a confederate deliver a speech in either a visibly anxious or confident manner. Participants rated their perception of the presenter's desirability across five attributes and compared themselves to the presenter along these same dimensions. Participants then delivered their own speeches, and were rated in a similar manner by trained research assistants who were naïve to participants' group status and study objectives. Results demonstrated that all participants, irrespective of group status, judged the visibly anxious presenter as being less desirable and the confident presenter as more desirable. Socially anxious participants tended to view themselves as inferior to confident others. Coders also rated participants with SAD, based on their speeches, as being less interpersonally desirable than HCs. These results suggest that individuals who appear visibly anxious may be objectively disadvantaged in their ability to make a positive first impression on others. We discuss these findings in relation to theoretical models of social anxiety and explore how to address such interpersonal factors in psychological interventions for SAD.

Negative social comparisons and psychosis proneness in a healthy adolescent population

There is growing evidence of an association between negative social comparisons (NSC) and both psychosis, and psychosis proneness. The majority of the work thus far, however, has focused largely on one type of NSC, namely, social rank. Whilst social rank is clearly an important factor, an individual's perception of belonging is likely also of importance; particularly, when considering individuals from collectivistic cultures such as China, where greater emphasis is placed on fitting into the group. There is also limited research investigating what factors may contribute towards the relationship between NSC and psychosis proneness, and to what extent this relationship may be due to common familial factors. To address these issues, we examined whether (1) Social rank and perceived belonging predict negative, positive and depressive psychotic experiences in a Chinese, adolescent, twin and sibling population, (2) coping styles moderate the impact of these relationships and (3), there is a familial association between NSC and psychosis proneness. Both social rank and perceived belonging were found to predict the negative and depressive dimensions of psychosis. These relationships were moderated by problem-focused coping styles. Interestingly, the association between perception of belonging, and negative psychotic experiences was familial-and stronger in Monozygotic twins-indicating perhaps shared aetiology due to common genes. Our findings highlight NSC as potential vulnerability markers for negative and depressive psychotic experiences, and suggest potentially different aetiological pathways amongst different NSC and different psychotic experiences. On a clinical level, our findings emphasize the need to consider coping styles when treating at-risk individuals.

The effect of unfavourable and favourable social comparisons on paranoid ideation: An experimental study

BACKGROUND AND OBJECTIVES

Low social rank is associated with paranoia, but there is a lack of evidence for causality. We tested the effects of social comparisons on negative affect and paranoia with an online social rank paradigm, and whether striving to avoid inferiority or fears of social rejection moderated paranoid reactions.

METHOD

Female students (N = 172) were randomly exposed to one of two validated online profiles depicting a same-aged, high (unfavourable comparison) vs. low rank (favourable comparison) female student. Moderators were assessed at baseline. Social rank, anxiety, sadness and paranoia were assessed pre and post profile-exposure.

RESULTS

There was a large effect of the experimental manipulation on social rank (p < 0.001, η²_partial = 0.191). The manipulations had no effects on anxiety and paranoia (p > 0.38). Sadness was significantly altered (p = 0.016, η²_partial = 0.033). There were significant moderation effects between the experimental conditions and insecure striving (trend-level) as well as fears of rejection.

LIMITATIONS

Our findings may be biased (overestimation of effects) as students are likely to be more competitive compared to the general population.

CONCLUSION

Our rank manipulations did not alter paranoia. This suggests that changes in the cognitive representation of social rank alone - without triggering a strong emotional response - do not suffice to evoke paranoia. Although our results do not support the notion that threats to social rank cause paranoid symptoms, they suggest that threats to social rank are more likely to trigger paranoid states in those who are insecure in regard to their social position.

Effects of social reorganization on dopamine D2/D3 receptor availability and cocaine self-administration in male cynomolgus monkeys

RATIONALE

Studies have demonstrated that brain dopamine D2/D3 receptors (D2/D3R) and the reinforcing effects of cocaine can be influenced by a monkey's position in the social dominance hierarchy.

OBJECTIVE

In this study, we manipulated the social ranks of monkeys by reorganizing social groups and assessed effects on D2/D3R availability and cocaine self-administration.

METHODS

Male cynomolgus monkeys (N = 12) had been trained to self-administer cocaine under a concurrent cocaine-food reinforcement schedule. Previously, PET measures of D2/D3R availability in the caudate nucleus and putamen had been obtained with [18F]fluoroclebopride during cocaine abstinence, while monkeys lived in stable social groups of four monkeys/pen. For this study, monkeys were reorganized into groups that consisted of (1) four previously dominant, (2) four previously subordinate, and (3) a mix of previously dominant and subordinate monkeys. After 3 months, D2/D3R availability was redetermined and cocaine self-administration was reexamined.

RESULTS

D2/D3R availability significantly increased after reorganization in monkeys who were formerly subordinate, with the greatest increases observed in those that became dominant. No consistent changes in D2/D3R availability were observed in formerly dominant monkeys. Cocaine self-administration did not vary according to rank after reorganization of social groups. However, when compared to their previous cocaine self-administration data, the potency of cocaine as a reinforcer decreased in 9 of 11 monkeys.

CONCLUSIONS

These results indicate that changing the social conditions can alter D2/D3R availability in subordinate monkeys in a manner suggestive of environmental enrichment. In most monkeys, social reorganization shifted the cocaine dose-response curve to the right, also consistent with environmental enrichment.

Socially dominant mice in C57BL6 background show increased social motivation

A series of behavioral tests measuring social dominance, social motivation, and non-social motivation are examined in adult male C57BL6 mice. By using the well-known tube dominance test to determine social dominance and rank, we find that, in the absence of competition for resource and mating, group-housed mouse cage-mates display stable and mostly linear and transitive social hierarchies. Mice with top and bottom social ranks are subjected to a three-chamber social interaction test to measure social motivation. The top ranked mice spend more time interacting with a stranger mouse than the bottom ranked mice, suggesting that social dominance may positively influence social motivation. When subjected to a novel environment, mice with different social ranks show similar locomotion and exploring activity in the open field test, suggesting no detectable difference in certain aspects of non-social motivation. These results demonstrate a behavioral correlation between social dominance and social motivation.

Social rank-dependent expression of gonadotropin-releasing hormones and kisspeptin in the medaka brain

Social interactions regulate the expression of several neuropeptides that have a central role in the reproductive system of mammals. Nonmammalian vertebrates also have these neuropeptides or paralogs, however, studies on the social regulation of reproductive physiology in nonmammalian species are limited. In this study, we examined whether the expression of gonadotropin-releasing hormones (GnRHs) and kisspeptin (Kiss1) is affected by social hierarchy resulting from the outcomes of male-male competition in medaka fish (Oryzias latipes). Four males were introduced to each other in an experimental tank, and classified as the most aggressive dominant or the most submissive subordinate fish, based on the frequency of their aggressive acts during a short-term competition. Dominant and subordinate males maintained their social rank during a long-term competition. Immediately after short-term competition, gonadotropin-releasing hormone-3 (GnRH3) level in the olfactory bulb was significantly higher in subordinate males than in dominant males. After long-term competition, dominant males had high level of gonadotropin-releasing hormone-1 (GnRH1) in the preoptic area, whereas subordinate males had lower Kiss1 level in the nucleus ventral tuberis. On the other hand, the levels of gonadotropin-releasing hormone-2 (GnRH2) in the nucleus lateralis valvulae and Kiss1 in the nucleus posterioris periventricularis, and plasma 11-ketotestosterone (11-KT) concentration did not differ between subordinate and dominant males after the short- and long-term competitions. These results suggest that social hierarchy regulates the expression of GnRH1, GnRH3, and Kiss1 without affecting 11-KT level in male medaka.

Social setting, social rank and HPA axis response in cynomolgus monkeys

RATIONALE

Hypothalamic-pituitary-adrenal (HPA) axis activity under different social settings in non-human primates is understudied.

OBJECTIVE

The aim of this study is to evaluate the response of pituitary-adrenal hormones (adrenocorticotropic hormone (ACTH) and cortisol) to pharmacological challenges of the HPA axis in male cynomolgus macaques under different social settings.

METHODS

Male cynomolgus macaques (Macaca fascicularis, n = 11) were individually (A) and socially housed (B) in alternation, over consecutive months, in an ABA design. During each experimental phase, plasma ACTH and cortisol were measured in response to low- and mild-intensity psychological stressors and following administration of saline, naloxone, ovine-corticotropin-releasing factor (oCRF), and dexamethasone.

RESULTS

These data demonstrate that cortisol measured under low stress conditions is sensitive to social rank (dominance hierarchy) and distinguishes dominant from non-dominant animals during both individual and social settings. Administration of naloxone resulted in elevated circulating ACTH and cortisol, while oCRF only increased circulating cortisol. During social housing, the cortisol response to naloxone and oCRF was increased, whereas dexamethasone suppression of ACTH and cortisol remained consistent across all social settings.

CONCLUSIONS

Circulating ACTH and cortisol are differentially sensitive to changes in social settings in non-human primates. Cortisol response increased during social housing and could be stimulated by both naloxone and oCRF, whereas ACTH response was generally not influenced by social setting or oCRF but was increased by naloxone. These data show differential adrenal and pituitary response to changes in social settings and a small, but consistent, effect of social dominance.

Involuntary processing of social dominance cues from bimodal face-voice displays

Social-rank cues communicate social status or social power within and between groups. Information about social-rank is fluently processed in both visual and auditory modalities. So far, the investigation on the processing of social-rank cues has been limited to studies in which information from a single modality was assessed or manipulated. Yet, in everyday communication, multiple information channels are used to express and understand social-rank. We sought to examine the (in)voluntary nature of processing of facial and vocal signals of social-rank using a cross-modal Stroop task. In two experiments, participants were presented with face-voice pairs that were either congruent or incongruent in social-rank (i.e. social dominance). Participants' task was to label face social dominance while ignoring the voice, or label voice social dominance while ignoring the face. In both experiments, we found that face-voice incongruent stimuli were processed more slowly and less accurately than were the congruent stimuli in the face-attend and the voice-attend tasks, exhibiting classical Stroop-like effects. These findings are consistent with the functioning of a social-rank bio-behavioural system which consistently and automatically monitors one's social standing in relation to others and uses that information to guide behaviour.

Towards evenly distributed grazing patterns: including social context in sheep management strategies

Background. A large proportion of natural grasslands around the world is exposed to overgrazing resulting in land degradation and biodiversity loss. Although there is an increasing effort in the promotion of sustainable livestock management, rangeland degradation still occurs because animals' foraging behaviour is highly selective at different spatial scales. The assessment of the ecological mechanisms modulating the spatial distribution of grazing and how to control it has critical implications for long term conservation of resources and the sustainability of livestock production. Considering the relevance of social interactions on animals' space use patterns, our aim was to explore the potential effects of including animals' social context into management strategies using domestic sheep grazing in rangelands as case study. Methods. We used GPS data from 19 Merino sheep (approximately 10% of the flock) grazing on three different paddocks (with sizes from 80 to 1000 Ha) during a year, to estimate resource selection functions of sheep grazing in flocks of different levels of heterogeneity. We assessed the effects of sheep class (i.e., ewes, wethers, and hoggets), age, body condition and time since release on habitat selection patterns. Results. We found that social rank was reflected on sheep habitat use, where dominant individuals (i.e., reproductive females) used more intensively the most preferred areas and low-ranked (i.e., yearlings) used less preferred areas. Our results showed that when sheep grazed on more heterogeneous flocks, grazing patterns were more evenly distributed at all the paddocks considered in this study. On the other hand, when high-ranked individuals were removed from the flock, low-ranked sheep shifted their selection patterns by increasing the use of the most preferred areas and strongly avoided to use less preferred sites (i.e., a highly selective grazing behaviour). Discussion. Although homogenization and segregation of flocks by classes are common practices to increase flock productivity, we are proposing an alternative that employs behavioural interactions in heterogeneous flocks to generate more evenly distributed grazing patterns. This practice can be combined with other practices such as rotational grazing and guardian dogs (to decrease mortality levels that may be generated by sheep grazing on more risky habitats). This does not imply any modifications of livestock stocking rates and densities or any additional investments for labour and materials. Considering livestock behaviour is critical for the design of sustainable management practices that balance landscape conservation and livestock productivity.

Judgments of Nonverbal Behaviour by Children with High-Functioning Autism Spectrum Disorder: Can they Detect Signs of Winning and Losing from Brief Video Clips?

Typically developing children are able to judge who is winning or losing from very short clips of video footage of behaviour between active match play across a number of sports. Inferences from "thin slices" (short video clips) allow participants to make complex judgments about the meaning of posture, gesture and body language. This study extends the use of the thin slice research paradigm to children with high-functioning autism spectrum disorder (ASD). We tested 38 children with ASD, in two age groups: 15 participants aged 5-8 years and 23 participants aged 9-13 years. We found that the children with ASD had a rate of accuracy similar to that of typically developing peers tested in a previous study.

Allelic variation of the COMT gene in a despotic primate society: A haplotype is related to cortisol excretion in Macaca fuscata

Sequence variations in genes of the monoamine neurotransmitter system and their common function in human and non-human primate species are an ongoing issue of investigation. However, the COMT gene, coding for the catechol-O-methyltransferase, has not yet attracted much scientific attention regarding its functional role in non-human primates. Considering that a polymorphism of the human COMT gene affects the enzyme activity and cortisol level in response to a social stressor, this study investigated the impact of COMT on endocrine stress and behavioural parameters in Japanese macaques (Macaca fuscata). The species exemplifies a despotic hierarchy in which males' social rank positions require an adaptation of behaviour strategies. During the mating period steroid secretion and the frequency of aggressive encounters between males increase. We addressed i) whether this species exhibits potential functional COMT variants, ii) whether these variants are associated with faecal cortisol excretion of males, iii) how they are distributed among different social rank positions and iv) whether they are associated with behavioural strategies during times of mate competition. By genotyping 26 males we identified three COMT haplotypes (HT), including a putative splice mutant (HT3). This variant was associated with increased cortisol excretion. Given the observed inverse correlation between cortisol and physical aggression, we assume that different COMT haplotypes may predispose individuals to pursue more or less aggressive strategies. How these gene-stress effects might favour a specific social role is discussed. Our study of non-invasive genotyping in combination with behavioural and endocrine parameters represents an important step towards the understanding of gene-stress effects in a hierarchically organised primate society.

Does income relate to health due to psychosocial or material factors? Consistent support for the psychosocial hypothesis requires operationalization with income rank not the Yitzhaki Index

Research on why income influences health has produced mixed findings. Many, but not all, studies suggest that the relationship between income and health is due to income indicating psychosocial position rather than the associated material benefits. The inconsistent findings may be partly due to the use of the Yitzhaki Index, a function which calculates the accumulated income shortfall for an individual relative to those with higher income, in order to represent the psychosocial position conferred by income. The current study tests whether an alternative specification - income rank - provides more consistent conclusions regarding the psychosocial effect of income on health. We used data from two nationally representative samples: 14,224 observations from 9,404 participants across three waves (2004, 2008, and 2012) of the English Longitudinal Study of Ageing (ELSA) and 29,237 observations from 8,441 individuals across seven waves (2007-2013) of the Longitudinal Internet Studies for the Social Sciences (LISS). Multilevel regression models indicated that income rank was a stronger and more consistent predictor than both the Yitzhaki Index and actual income of self-rated and objective health. The psychosocial hypothesis is more consistently supported when income rank is used to test it.

Why does Income Relate to Depressive Symptoms? Testing the Income Rank Hypothesis Longitudinally

This paper reports a test of the relative income rank hypothesis of depression, according to which it is the rank position of an individual's income amongst a comparison group, rather than the individual's absolute income, that will be associated with depressive symptoms. A new methodology is developed to test between psychosocial and material explanations of why income relates to well-being. This method was used to test the income rank hypothesis as applied to depressive symptoms. We used data from a cohort of 10,317 individuals living in Wisconsin who completed surveys in 1992 and 2003. The utility assumed to arise from income was represented with a constant relative risk aversion function to overcome limitations of previous work in which inadequate specification of the relationship between absolute income and well-being may have inappropriately favoured relative income specifications. We compared models in which current and future depressive symptoms were predicted from: (a) income utility alone, (b) income rank alone, (c) the transformed difference between the individual's income and the mean income of a comparison group and (d) income utility, income rank and distance from the mean jointly. Model comparison overcomes problems involving multi-collinearity amongst the predictors. A rank-only model was consistently supported. Similar results were obtained for the association between depressive symptoms and wealth and rank of wealth in a cohort of 32,900 British individuals who completed surveys in 2002 and 2008. We conclude that it is the rank of a person's income or wealth within a social comparison group, rather than income or wealth themselves or their deviations from the mean within a reference group, that is more strongly associated with depressive symptoms.

Height, social comparison, and paranoia: an immersive virtual reality experimental study

Mistrust of others may build upon perceptions of the self as vulnerable, consistent with an association of paranoia with perceived lower social rank. Height is a marker of social status and authority. Therefore we tested the effect of manipulating height, as a proxy for social rank, on paranoia. Height was manipulated within an immersive virtual reality simulation. Sixty females who reported paranoia experienced a virtual reality train ride twice: at their normal and reduced height. Paranoia and social comparison were assessed. Reducing a person's height resulted in more negative views of the self in comparison with other people and increased levels of paranoia. The increase in paranoia was fully mediated by changes in social comparison. The study provides the first demonstration that reducing height in a social situation increases the occurrence of paranoia. The findings indicate that negative social comparison is a cause of mistrust.

Impression formation and revision in social anxiety disorder

Interpersonal relations are markedly impaired in social anxiety. Yet, little is known about the ways social anxiety affects social cognition. We examined impression formation and impression revision among individuals with social anxiety disorder (SAD, n = 26) and non-anxious individuals (n = 29). Participants read initial descriptions of protagonists depicted as dominant, neutral or submissive and rated them on social rank and affiliation dimensions. Next, participants were presented with behavioral acts that were either congruent, incongruent or irrelevant to the initial descriptions, and re-rated the protagonists. Individuals with SAD (a) rated others as more extreme on social rank dimension, (b) rated others as lower on the affiliation dimension, and (c) revised their impressions of others to a greater extent than did the non-anxious individuals. Understanding the ways social anxiety affects the formation and revision of perceptions of others can improve our understanding of maintaining processes in SAD.

Food availability and competition do not modulate the costs of Plasmodium infection in dominant male canaries

Understanding the different factors that may influence parasite virulence is of fundamental interest to ecologists and evolutionary biologists. It has recently been demonstrated that parasite virulence may occur partly through manipulation of host competitive ability. Differences in competitive ability associated with the social status (dominant or subordinate) of a host may determine the extent of this competition-mediated parasite virulence. We proposed that differences between subordinate and dominant birds in the physiological costs of infection may change depending on the level of competition in social groups. We observed flocks of domestic canaries to determine dominant or subordinate birds, and modified competition by providing restricted (high competition) or ad libitum food (low competition). Entire flocks were then infected with either the avian malaria parasite, Plasmodium relictum or a control. Contrary to our predictions we found that the level of competition had no effect on the outcome of infection for dominant or subordinate birds. We found that dominant birds appeared to suffer greater infection mediated morbidity in both dietary treatments, with a higher and more sustained reduction in haematocrit, and higher parasitaemia, than subordinates. Our results show that dominance status in birds can certainly alter parasite virulence, though the links between food availability, competition, nutrition and virulence are likely to be complex and multifaceted.

Social interactions modulate the virulence of avian malaria infection

There is an increasing understanding of the context-dependent nature of parasite virulence. Variation in parasite virulence can occur when infected individuals compete with conspecifics that vary in infection status; virulence may be higher when competing with uninfected competitors. In vertebrates with social hierarchies, we propose that these competition-mediated costs of infection may also vary with social status. Dominant individuals have greater competitive ability than competing subordinates, and consequently may pay a lower prevalence-mediated cost of infection. In this study we investigated whether costs of malarial infection were affected by the occurrence of the parasite in competitors and social status in domestic canaries (Serinus canaria). We predicted that infected subordinates competing with non-infected dominants would pay higher costs than infected subordinates competing with infected dominants. We also predicted that these occurrence-mediated costs of infection would be ameliorated in infected dominant birds. We found that social status and the occurrence of parasites in competitors significantly interacted to change haematocrit in infected birds. Namely, subordinate and dominant infected birds differed in haematocrit depending on the infection status of their competitors. However, in contrast to our prediction, dominants fared better with infected subordinates, whereas subordinates fared better with uninfected dominants. Moreover, we found additional effects of parasite occurrence on mortality in canaries. Ultimately, we provide evidence for costs of parasitism mediated by social rank and the occurrence of parasites in competitors in a vertebrate species. This has important implications for our understanding of the evolutionary processes that shape parasite virulence and group living.

Absolute and relative family affluence and psychosomatic symptoms in adolescents

Previous research on the links between income inequality and health and socioeconomic differences in health suggests that relative differences in affluence impact health and well-being more than absolute affluence. This study explored whether self-reported psychosomatic symptoms in adolescents relate more closely to relative affluence (i.e., relative deprivation or rank affluence within regions or schools) than to absolute affluence. Data on family material assets and psychosomatic symptoms were collected from 48,523 adolescents in eight countries (Austria, Belgium, Canada, Norway, Scotland, Poland, Turkey, and Ukraine) as part of the 2009/10 Health Behaviour in School-aged Children study. Multilevel regression analyses of the data showed that relative deprivation (Yitzhaki Index, calculated in regions and in schools) and rank affluence (in regions) (1) related more closely to symptoms than absolute affluence, and (2) related to symptoms after differences in absolute affluence were held constant. However, differences in family material assets, whether they are measured in absolute or relative terms, account for a significant variation in adolescent psychosomatic symptoms. Conceptual and empirical issues relating to the use of material affluence indices to estimate socioeconomic position are discussed.

Avian predation upon a mixed community of common voles (Microtus arvalis) and wood mice (Apodemus sylvaticus)

Pellets of diurnal avian predators (mainly kestrels and buzzards) were analysed to prove the hypothesis of selective predation for a mixed population of small rodents. It was found that voles heavily predominated as prey over mice (up to a factor of 19 during winter). Within both prey species, predation focussed on distinct parts of the populations: during winter the heaviest specimens were preferentially captured, during summer the subadults were in an exposed position. In the voles, an additional predominance of males occurred (up to a factor of 5.2 during summer). These findings verify the assumption of Errington (1956) that speciments of a low social rank are susceptible to the highest risk of predation.