The relationship of personality dimensions in adult male rhesus macaques to progression of simian immunodeficiency virus disease

Are bold-shy personalities of European perch (Perca fluviatilis) linked to stress tolerance and immunity? A scope of harnessing fish behavior in aquaculture

The sensitivity to stress and its impact on immunity are supposedly related to a fish's personality. In the present study, European perch (Perca fluviatilis) were exposed to an open-field and a novel-object test to identify distinctive shy and bold individuals. This series of cognitive tests revealed clear differences between proactive individuals with pronounced exploration behavior (bold personality) and reactive individuals that took a freeze-hide position (shy personality). A cohort of shy and bold perch was then exposed to elevated stocking density. Frozen activity and lower explorative behavior were related to higher basal and stocking-induced cortisol levels compared to proactive individuals. Since cortisol is a well-known modulator of immune-gene expression, we used multiplex real-time PCR to profile the differential immune responses to the intraperitoneal injection of Aeromonas hydrophila in the head kidney and peritoneal cells of bold and shy perch individuals. These expression differences between stimulated bold and shy perch were generally modest, except for the genes encoding the complement component c3 and the matrix metallopeptidase mmp9. The strong differential expression of these two bactericidal and inflammatory genes in the context of the modestly regulated features suggests that a fish's personality is linked to a particular immune-defense strategy. In conclusion, our approach, based on behavioral video observations, phagocytosis and enzyme assays, immunogene-expression profiling, and quantification of stress-relevant metabolites, revealed indications for divergent coping styles in cohorts of bold or shy European perch. This divergence could be exploited in future selective breeding programs.

Judgement bias of group housed gestating sows predicted by behavioral traits, but not physical measures of welfare

Judgement bias testing has emerged as a potential tool for assessing affective states in animals. Researchers infer an animal's affective state based on an animal's response to an ambiguous stimulus that is intermediate to both the rewarded and punished conditioned stimuli. Animals can be classified as "optimistic" or having a positive affective state if the animal displays behaviors that suggest an increased expectation of reward in the face of ambiguous stimuli. Alternatively, animals can be classified "pessimistic" or having a negative affective state if the animal displays behaviors that suggest an increased expectation of punishment in the face of ambiguous stimuli. Recent reports in multiple species question what factors influence performance in judgement bias testing, and which may allow for erroneous conclusions regarding individual affective state. In order to better understand this concern, 25 female swine were subjected to behavioral assessments at critical rearing stages to determine response variability. These same individuals were then assessed for physical measures of welfare and judgement bias using the "go/no-go" task as breeding adults. Sows which were more aggressive approached the ambiguous, but not the positive, stimulus significantly faster than others. Both optimistic and pessimistic biases were observed despite all sows living in enriched housing, and, sows with more positive physical welfare measures (fewer skin lesions and healthy body condition) did not exhibit more optimistic judgement biases. Our data demonstrate that behavior traits, such as aggressiveness, can affect a sow's performance in a judgement bias test, while measures of physical health did not. We suggest that individual differences in behavior (e.g., bold-aggressive behavioral syndrome, or, proactive coping style) generate different emotional responses and can contribute to the animal's overall affective state more so than physical ailment. Our findings highlight the complexity of how different factors impact an animal's overall affective state and support the need for complementary measures in future JBT studies, including personality assessment.

The relationship between personality, season, and wounding receipt in zoo-housed Japanese macaques (Macaca fuscata): A multi-institutional study

It is important to those managing Japanese macaques (Macaca fuscata) in captive settings to understand predictors of wounding. While studies have demonstrated that season (breeding or nonbreeding) and sex predict rates of wounding received by zoo-housed Japanese macaques, we investigated whether individual differences in personality ratings also might explain some of the observed interindividual variance in wounding. Such patterns were previously observed in rhesus macaques (M. mulatta), such that individuals rated higher on Anxiety and Confidence received greater wounding. Here, we collected wounding data over 24 months on 48 Japanese macaques from eight AZA-accredited zoos. Each macaque was also rated by keepers using a 26-item personality questionnaire. Principle components analysis of these ratings revealed four personality components: Openness, Friendliness, Dominance, and Anxiety/Reactivity. The model with the best fit revealed an interaction effect between season (breeding vs. nonbreeding) and the personality component Friendliness, such that individuals rated higher on Friendliness incurred fewer wounds in the nonbreeding season. The second-best model revealed both a main effect of the season as well as an interaction effect between season and Openness, such that macaques rated higher in Openness received more wounds in the nonbreeding season than those rated lower in Openness. Thus, as with rhesus macaques, personality mediated wounding receipt rate in Japanese macaques, although different personality components explained interindividual variance in wounding for these two species. These differences likely reflect species differences in behavior and personality structure, as well as the influence of differing management practices, highlighting the importance of species-specific approaches for captive primate care and welfare. This study provides further support for understanding primate personality to create individualized strategies for their care.

Gaps to Address in Ecological Studies of Temperament and Physiology

Ecology is a diverse field with many researchers interested in drivers and consequences of variability within populations. Two aspects of variability that have been addressed are behavioral and physiological. While these have been shown to separately influence ecological outcomes such as survival, reproductive success and fitness, combined they could better predict within-population variability in survival and fitness. Recently there has been a focus on potential fitness outcomes of consistent behavioral traits that are referred to as personality or temperament (e.g. boldness, sociability, exploration, etc.). Given this recent focus, it is an optimal time to identify areas to supplement in this field, particularly in determining the relationship between temperament and physiological traits. To maximize progress, in this perspective paper we propose that the following two areas be addressed: (1) increased diversity of species, and (2) increased number of physiological processes studied, with an eye toward using more representative and relatively consistent measures across studies. We first highlight information that has been gleaned from species that are frequently studied to determine how animal personality relates to physiology and/or survival/fitness. We then shine a spotlight on important taxa that have been understudied and that can contribute meaningful, complementary information to this area of research. And last, we propose a brief array of physiological processes to relate to temperament, and that can significantly impact fitness, and that may be accessible in field studies.

Patterns and variation in the mammal parasite-glucocorticoid relationship

Parasites are ubiquitous and can strongly affect their hosts through mechanisms such as behavioural changes, increased energetic costs and/or immunomodulation. When parasites are detrimental to their hosts, they should act as physiological stressors and elicit the release of glucocorticoids. Alternatively, previously elevated glucocorticoid levels could facilitate parasite infection due to neuroimmunomodulation. However, results are equivocal, with studies showing either positive, negative or no relationship between parasite infection and glucocorticoid levels. Since factors such as parasite type, infection severity or host age and sex can influence the parasite-glucocorticoid relationship, we review the main mechanisms driving this relationship. We then perform a phylogenetic meta-analysis of 110 records from 65 studies in mammalian hosts from experimental and observational studies to quantify the general direction of this relationship and to identify ecological and methodological drivers of the observed variability. Our review produced equivocal results concerning the direction of the relationship, but there was stronger support for a positive relationship, although causality remained unclear. Mechanisms such as host manipulation for parasite survival, host response to infection, cumulative effects of multiple stressors, and neuro-immunomodulatory effects of glucocorticoids could explain the positive relationship. Our meta-analysis results revealed an overall positive relationship between glucocorticoids and parasitism among both experimental and observational studies. Because all experimental studies included were parasite manipulations, we conclude that parasites caused in general an increase in glucocorticoid levels. To obtain a better understanding of the directionality of this link, experimental manipulation of glucocorticoid levels is now required to assess the causal effects of high glucocorticoid levels on parasite infection. Neither parasite type, the method used to assess parasite infection nor phylogeny influenced the relationship, and there was no evidence for publication bias. Future studies should attempt to be as comprehensive as possible, including moderators potentially influencing the parasite-glucocorticoid relationship. We particularly emphasise the importance of testing hosts of a broad age range, concomitantly measuring sex hormone levels or at least reproductive status, and for observational studies, also considering food availability, host body condition and social stressors to obtain a better understanding of the parasite-glucocorticoid relationship.

Behavioral predictors of subsequent respiratory illness signs in dogs admitted to an animal shelter

Individual variability is evident in behavior and physiology of animals. Determining whether behavior at intake may predict subsequent illness in the animal shelter may influence the management of dogs housed at animal shelters and reduce overall disease. While normally associated with mild disease and low mortality rates, respiratory disease nevertheless poses significant challenges to the management of dogs in the stressful environment of animal shelters due to its highly infectious nature. Therefore, the aim of the study was to explore whether behavior at intake can predict subsequent occurrence and progression of upper respiratory disease in dogs at animal shelters. In a correlational study, 84 dogs were assessed throughout their stay at a city animal shelter. The dogs were subjected to a behavioral assessment, 1 min in-kennel behavioral observations across two observation periods, and the collection of urinary cortisol:creatinine (C:C) ratio. The occurrence and progression of upper respiratory disease was monitored through repeated clinical exams (rectal temperature and the occurrence of nasal and ocular discharge, and presence of coughing and sneezing). A basic PLS Path regression model revealed that time in the shelter (estimate = .53, p < .001), and sociability (estimate = .24, p < .001) and curiosity scores (estimate = .09, p = .026) were associated with increased illness. Activity and anxiety scores, however, were not associated with illness. Urinary C:C, taken on the first full day, did not predict subsequent illness when accounting for time. Limitations included attrition of dogs, a small percentage receiving vaccinations, and continuous and non-systematic rotation of dogs in the kennels. Understanding if behavior can predict subsequent illness may improve shelter management practices, and in turn, result in improved live-release outcomes.

Social Environment and Individual Differences in Feeding Behavior Are Associated with Risk of Endometritis in Dairy Cows

Simple Summary

The aim of this study was to determine how individual differences in behavior affect disease risk in Holstein dairy cows housed in two different social environments: (1) a predictable and non-competitive social environment and (2) an unpredictable and competitive social environment. Individual differences in feed intake and feeding behavior before calving were associated with cytological endometritis post-calving; however, the direction and magnitude of these effects were dependent on the social environment. These results provide the first evidence that individual differences in feeding behavior affect cytological endometritis risk differently depending on the social environment.

Abstract

Our aim was to determine whether individual differences in feeding and social behavior in different social environments affect health outcomes in dairy cows. We used eight groups of four animals per treatment assigned to either a ‘predictable’ or an ‘unpredictable’ and competitive social environment. Predictable cows were given free access to six feed bins with no change in feed delivery times; whereas, the unpredictable cows were required to share one feed bin with one resident cow and morning feed was delayed 0, 1, 2, or 3 h every other day. On alternate days, the unpredictable cows were also re-assigned to a new bin and a new resident partner. Low daily dry matter intake (DMI) was a risk factor for cytological endometritis in predictable cows (odds ratio (OR) (95% confidence interval): 0.17 (0.02, 0.53)), but low daily DMI was protective for unpredictable cows (OR: 1.93 (1.09, 4.14)). Although low rate of DMI (kg/min) was a risk factor for cytological endometritis for predictable cows (OR: 4.2 × 10⁻¹⁰¹ (8.6 × 10⁻²⁰⁶, 4.8 × 10⁻³⁰)) it was unrelated to disease for unpredictable cows. There were no associations between feed bin visits or percentage of non-nutritive visits with the likelihood of cytological endometritis. This is the first evidence that individual differences in feeding behavior influence cytological endometritis risk in dairy cows, but the direction and magnitude of these effects is dependent on the social environment.

Personality, environmental stressors, and diarrhea in Rhesus macaques: An interactionist perspective

Previous research has repeatedly shown both personality and psychological stress to predict gastrointestinal disorders and chronic diarrhea in humans. The goal of the present research was to evaluate the role of personality, as well as psychological stressors (i.e., housing relocations and rearing environment), in predicting chronic diarrhea in captive Rhesus macaques, with particular attention to how personality regulated the impact of such stressors. Subjects were 1,930 R. macaques at the California National Primate Research Center reared in a variety of environments. All subjects took part in an extensive personality evaluation at approximately 90-120 days of age. Data were analyzed using generalized linear models to determine how personality, rearing condition, housing relocations, and personality by environment interactions, predicted both diarrhea risk (an animal's risk for having diarrhea at least once) and chronic diarrhea (how many repeated bouts of diarrhea an animal had after their initial bout). Much like the human literature, we found that certain personality types (i.e., nervous, gentle, vigilant, and not confident) were more likely to have chronic diarrhea, and that certain stressful environments (i.e., repeated housing relocations) increased diarrhea risk. We further found multiple interactions between personality and environment, supporting the "interactionist" perspective on personality and health. We conclude that while certain stressful environments increase risk for chronic diarrhea, the relative impact of these stressors is highly dependent on an animal's personality.

A human model for primate personality

In this article, I review the literature to determine how successful the latent trait theory model of personality from differential psychology has been for studying personality in non-human primates. The evidence for the success of this model is quite good, and offers insights and directions for personality research in primates and other animals. This, I conclude, stems from (i) the human trait model's simplicity, and (ii) the fact that the human differential model of personality developed in the face of harsh criticism, which led researchers to test and refine their models.

Bold personality makes domestic dogs entering a shelter less vulnerable to diseases

It is widely recognised that for vertebrate species, personalities vary along an axis with extremes represented by ‘proactive’ and ‘reactive‘ individuals. The aim of this study was to verify whether there is a relationship between personality and disease vulnerability in domestic dogs (Canis familiaris) exposed to an intensely stressful situation such as entering a shelter. Twenty-eight shelter dogs participated in the study. The ethogram consisted of approximately 100 behavioural patterns. Behavioural observations of dogs in their new environment, a Novel Object and a T-maze test were used to evaluate the personality of the dogs captured as strays and entering the shelter. A blood sample from each dog was obtained at admission into the shelter and after a month to evaluate their immunological state. Based on PCA analyses of observational combined with experimental data, the dogs were ordered along the boldness-shyness axis, with the first being the boldest. Excluding one (the 6th), the first 10 dogs showed an improved health status: absence of disease symptoms during the 30 days of monitoring and improved immunological parameters; the opposite was found for shy dogs. The results of this research seem to confirm findings in other vertebrate species, i.e., bold and shy dog vulnerability to diseases might be different, especially when they must cope with a stressful and highly infectious environment such as a dog shelter.

Rhesus macaque personality, dominance, behavior, and health

Previous studies of nonhuman primates have found relationships between health and individual differences in personality, behavior, and social status. However, despite knowing these factors are intercorrelated, many studies focus only on a single measure, for example, rank. Consequently, it is difficult to determine the degree to which these individual differences are independently associated with health. The present study sought to untangle the associations between health and these individual differences in rhesus macaques (Macaca mulatta). We studied 85 socially housed macaques at the Oregon and California National Primate Research Centers, and used veterinary records to determine the number of injuries and illnesses for each macaque. We measured personality using 12 items from a well-established primate personality questionnaire, performed focal observations of behaviors, and calculated dominance status from directional supplant data. All twelve personality questionnaire items were reliable and were used to represent five of the six personality dimensions identified in rhesus macaques-Dominance, Confidence, Openness, Anxiety, and Friendliness (also known as Sociability). Following this, we fit generalized linear mixed effects models to understand how these factors were associated with an animal's history of injury and history of illness. In the models, age was an offset, facility was a random effect, and the five personality dimensions, behavior, sex, and dominance status were fixed effects. Number of injuries and illnesses were each best represented by a negative binomial distribution. For the injury models, including the effects did improve model fit. This model revealed that more confident and more anxious macaques experienced fewer injuries. For the illness models, including the fixed effects did not significantly improve model fit over a model without the fixed effects. Future studies may seek to assess mechanisms underlying these associations.

Ontogeny of behavioral traits in commercial sows

As the number of gestating sows reared in group housing increases, a better understanding of behavioral traits needed to negotiate these more complex social interactions promises to increase animal welfare and productivity. However, little is known about different behavioral strategies or coping styles in sows, and even less is understood about their ontogeny. To study the development of coping styles in adult gestating sows, 36 sows from the same sire line and same commercial maternal genetics were followed from birth through their second parity. Each animal was observed in a battery of stress-related behavioral tests at 5 weeks, and 3 months of age as well as 24 h postpartum as a parity 1 sow, and during introduction to subsequent gestation period in group housing. The tests at different ages included response to handling, open field exploration, human interaction, litter handling and social interactions with conspecifics. Many of the observed behaviors were correlated during the same period of the animal's life and provided the motivation for a principal component analysis by age. Using principal component analysis, multiple traits were determined at each age point; at 5 weeks old: active, non-exploratory and cautious explained 82.5% of the variance; at 3 months of age: active, non-exploratory and low fear of humans explained 87.7% of the variance; and as primiparous sows: active, aggressive/dominant and submissive explained 82.0% of the variance. Several individual juvenile behaviors were associated with adult behavioral traits. For instance, the response to handling at 5 weeks was significantly predictive (β=0.4; P<0.05) of the aggressive/dominant trait of parity 1 sows. Taken together results presented here suggest that early behavioral responses of prepuberal gilts during specific instances of elevated environmental or social stress can predict future behavioral response as gestating sows.

Social regulation of the lymph node transcriptome in rhesus macaques (Macaca mulatta)

Previous research has shown that adverse social conditions may promote a conserved transcriptional response to adversity (CTRA) involving up-regulation of proinflammatory gene expression and down-regulation of Type I interferon anti-viral genes in circulating blood cells. However, the impact of social conditions on lymphoid tissue gene regulation remains largely unexplored. This project assessed how social instability in adult male rhesus macaques (N=10, 5 in unstable, and 5 in stable social conditions) might regulate gene expression within secondary lymphoid tissue (lymph nodes; LN). Unstable social conditions down-regulated axillary LN expression of genes involved in Type I interferon anti-viral responses. Transcript origin analyses implicated monocytes and B cells as cellular mediators of these effects, and promoter-based bioinformatics analyses indicated reduced activity of AP-1, NF-κB, IRF, and CREB transcription factors within the axillary LN microenvironment. Although the current study is limited in sample size, these results suggest that social influences on immune cell gene regulation extend beyond the circulating leukocyte pool to alter generalized transcriptome profiles in secondary lymphoid tissue, and they do so in a regulatory program that resembles the pattern of antiviral inhibition previously observed in circulating leukocytes.

Why are behavioral and immune traits linked?

Through behavior, animals interact with a world where parasites abound. It is easy to understand how behavioral traits can thus have a differential effect on pathogen exposure. Harder to understand is why we observe behavioral traits to be linked to immune defense traits. Is variation in immune traits a consequence of behavior-induced variation in immunological experiences? Or is variation in behavioral traits a function of immune capabilities? Is our immune system a much bigger driver of personality than anticipated? In this review, I provide examples of how behavioral and immune traits co-vary. I then explore the different routes linking behavioral and immune traits, emphasizing on the physiological/hormonal mechanisms that could lead to immune control of behavior. Finally, I discuss why we should aim at understanding more about the mechanisms connecting these phenotypic traits.

Early Predictors of Impaired Social Functioning in Male Rhesus Macaques (Macaca mulatta)

Autism spectrum disorder (ASD) is characterized by social cognition impairments but its basic disease mechanisms remain poorly understood. Progress has been impeded by the absence of animal models that manifest behavioral phenotypes relevant to ASD. Rhesus monkeys are an ideal model organism to address this barrier to progress. Like humans, rhesus monkeys are highly social, possess complex social cognition abilities, and exhibit pronounced individual differences in social functioning. Moreover, we have previously shown that Low-Social (LS) vs. High-Social (HS) adult male monkeys exhibit lower social motivation and poorer social skills. It is not known, however, when these social deficits first emerge. The goals of this study were to test whether juvenile LS and HS monkeys differed as infants in their ability to process social information, and whether infant social abilities predicted later social classification (i.e., LS vs. HS), in order to facilitate earlier identification of monkeys at risk for poor social outcomes. Social classification was determined for N = 25 LS and N = 25 HS male monkeys that were 1-4 years of age. As part of a colony-wide assessment, these monkeys had previously undergone, as infants, tests of face recognition memory and the ability to respond appropriately to conspecific social signals. Monkeys later identified as LS vs. HS showed impairments in recognizing familiar vs. novel faces and in the species-typical adaptive ability to gaze avert to scenes of conspecific aggression. Additionally, multivariate logistic regression using infant social ability measures perfectly predicted later social classification of all N = 50 monkeys. These findings suggest that an early capacity to process important social information may account for differences in rhesus monkeys' motivation and competence to establish and maintain social relationships later in life. Further development of this model will facilitate identification of novel biological targets for intervention to improve social outcomes in at-risk young monkeys.

Connections Matter: Social Networks and Lifespan Health in Primate Translational Models

Humans live in societies full of rich and complex relationships that influence health. The ability to improve human health requires a detailed understanding of the complex interplay of biological systems that contribute to disease processes, including the mechanisms underlying the influence of social contexts on these biological systems. A longitudinal computational systems science approach provides methods uniquely suited to elucidate the mechanisms by which social systems influence health and well-being by investigating how they modulate the interplay among biological systems across the lifespan. In the present report, we argue that nonhuman primate social systems are sufficiently complex to serve as model systems allowing for the development and refinement of both analytical and theoretical frameworks linking social life to health. Ultimately, developing systems science frameworks in nonhuman primate models will speed discovery of the mechanisms that subserve the relationship between social life and human health.

The correlation between alopecia and temperament in rhesus macaques (Macaca mulatta) at four primate facilities

Alopecia is a ubiquitous, multifaceted problem at facilities caring for captive rhesus macaques. There is a wide range of potential etiologies for the hair loss, including compromised immune function, dermatological pathologies, and environmental factors. However, few studies have examined whether various temperamental traits affect vulnerability to develop alopecia. We examined the correlation between alopecia and temperament in 101 (51M) indoor-housed rhesus macaques at four national primate centers. We utilized a cage side version of the Human Intruder test (HIT) to assess response to four conditions: no human present (Alone), human intruder standing next to the cage without making eye contact (Profile), intruder making direct eye contact (Stare) and intruder with back turned (Back). Behavior from all videos was quantified at one facility. We used generalized linear modeling to examine the relationship between behavior on the HIT and alopecia, controlling for facility, age, and sex. There was a significant negative correlation between alopecia and various behaviors associated with an inhibited or anxious temperament, including self-directed behavior (β = -0.15, P < 0.001) and freeze in the Profile period (β = -0.0092, P < 0.001), and defensive behaviors (β = -0.0094, P < 0.001) and time spent in the back of the cage in the Stare period (β = -0.0023, P = 0.015). Individuals with an inhibited or anxious temperament had less alopecia than others. Further, there were facility differences with respect to several variables on the HIT, including defensive behavior in Stare and freeze in Profile. These results suggest that temperament can influence the development of alopecia in rhesus macaques. Our results also highlight the degree to which facility differences can affect outcomes on standardized behavioral tests. Am. J. Primatol. 79:e22504, 2017. © 2015 Wiley Periodicals, Inc.

Personality and gene expression: Do individual differences exist in the leukocyte transcriptome?

BACKGROUND

The temporal and situational stability of personality has led generations of researchers to hypothesize that personality may have enduring effects on health, but the biological mechanisms of such relationships remain poorly understood. In the present study, we utilized a functional genomics approach to examine the relationship between the 5 major dimensions of personality and patterns of gene expression as predicted by 'behavioural immune response' theory. We specifically focussed on two sets of genes previously linked to stress, threat, and adverse socio-environmental conditions: pro-inflammatory genes and genes involved in Type I interferon and antibody responses.

METHODS

An opportunity sample of 121 healthy individuals was recruited (86 females; mean age 24 years). Individuals completed a validated measure of personality; questions relating to current health behaviours; and provided a 5ml sample of peripheral blood for gene expression analysis.

RESULTS

Extraversion was associated with increased expression of pro-inflammatory genes and Conscientiousness was associated with reduced expression of pro-inflammatory genes. Both associations were independent of health behaviours, negative affect, and leukocyte subset distributions. Antiviral and antibody-related gene expression was not associated with any personality dimension.

CONCLUSIONS

The present data shed new light on the long-observed epidemiological associations between personality, physical health, and human longevity. Further research is required to elucidate the biological mechanisms underlying these associations.

Genetic influences on response to novel objects and dimensions of personality in Papio baboons

Behavioral variation within and between populations and species of the genus Papio has been studied extensively, but little is known about the genetic causes of individual- or population-level differences. This study investigates the influence of genetic variation on personality (sometimes referred to as temperament) in baboons and identifies a candidate gene partially responsible for the variation in that phenotype. To accomplish these goals, we examined individual variation in response to both novel objects and an apparent novel social partner (using a mirror test) among pedigreed baboons (n = 578) from the Southwest National Primate Research Center. We investigated the frequency and duration of individual behaviors in response to novel objects and used multivariate factor analysis to identify trait-like dimensions of personality. Exploratory factor analysis identified two distinct dimensions of personality within this population. Factor 1 accounts for 46.8 % of the variance within the behavioral matrix, and consists primarily of behaviors related to the "boldness" of the subject. Factor 2 accounts for 18.8 % of the variation, and contains several "anxiety" like behaviors. Several specific behaviors, and the two personality factors, were significantly heritable, with the factors showing higher heritability than most individual behaviors. Subsequent analyses show that the behavioral reactions observed in the test protocol are associated with animals' social behavior observed later in their home social groups. Finally we used linkage analysis to map quantitative trait loci for the measured phenotypes. Single nucleotide polymorphisms in a positional candidate gene (SNAP25) are associated with variation in one of the personality factors, and CSF levels of homovanillic acid and 3-methoxy-4-hydroxyphenylglycol. This study documents heritable variation in personality among baboons and suggests that sequence variation in SNAP25 may influence differences in behavior and neurochemistry in these nonhuman primates.

Risk factors for stereotypic behavior and self-biting in rhesus macaques (Macaca mulatta): animal's history, current environment, and personality

Captive rhesus macaques sometimes exhibit undesirable abnormal behaviors, such as motor stereotypic behavior (MSB) and self-abuse. Many risk factors for these behaviors have been identified but the list is far from comprehensive, and large individual differences in rate of behavior expression remain. The goal of the current study was to determine which experiences predict expression of MSB and self-biting, and if individual differences in personality can account for additional variation in MSB expression. A risk factor analysis was performed utilizing data from over 4,000 rhesus monkeys at the California National Primate Research Center. Data were analyzed using model selection, with the best fitting models evaluated using Akaike Information Criterion. Results confirmed previous research that males exhibit more MSB and self-biting than females, MSB decreases with age, and indoor reared animals exhibit more MSB and self-biting than outdoor reared animals. Additionally, results indicated that animals exhibited less MSB and self-biting for each year spent outdoors; frequency of room moves and number of projects positively predicted MSB; pair separations positively predicted MSB and self-biting; pair housed animals expressed less MSB than single housed and grate paired animals; and that animals expressed more MSB and self-biting when in bottom rack cages, or cages near the room entrance. Based on these results we recommend limiting exposure to these risk factors when possible. Our results also demonstrated a relationship between personality and MSB expression, with animals low on gentle temperament, active in response to a human intruder, and high on novel object contact expressing more MSB. From these results we propose that an animal's MSB is related to its predisposition for an active personality, with active animals expressing higher rates of MSB.

Cortisol patterns are associated with T cell activation in HIV

Objective

The level of T cell activation in untreated HIV disease is strongly and independently associated with risk of immunologic and clinical progression. The factors that influence the level of activation, however, are not fully defined. Since endogenous glucocorticoids are important in regulating inflammation, we sought to determine whether less optimal diurnal cortisol patterns are associated with greater T cell activation.

Methods

We studied 128 HIV-infected adults who were not on treatment and had a CD4⁺ T cell count above 250 cells/µl. We assessed T cell activation by CD38 expression using flow cytometry, and diurnal cortisol was assessed with salivary measurements.

Results

Lower waking cortisol levels correlated with greater T cell immune activation, measured by CD38 mean fluorescent intensity, on CD4⁺ T cells (r = −0.26, p = 0.006). Participants with lower waking cortisol also showed a trend toward greater activation on CD8⁺ T cells (r = −0.17, p = 0.08). A greater diurnal decline in cortisol, usually considered a healthy pattern, correlated with less CD4⁺ (r = 0.24, p = 0.018) and CD8⁺ (r = 0.24, p = 0.017) activation.

Conclusions

These data suggest that the hypothalamic-pituitary-adrenal (HPA) axis contributes to the regulation of T cell activation in HIV. This may represent an important pathway through which psychological states and the HPA axis influence progression of HIV.

Personality is of central concern to understand health: towards a theoretical model for health psychology

This paper sets out the case that personality traits are central to health psychology. To achieve this, three aims need to be addressed. First, it is necessary to show that personality influences a broad range of health outcomes and mechanisms. Second, the simple descriptive account of Aim 1 is not sufficient, and a theoretical specification needs to be developed to explain the personality-health link and allow for future hypothesis generation. Third, once Aims 1 and 2 are met, it is necessary to demonstrate the clinical utility of personality. In this review I make the case that all three Aims are met. I develop a theoretical framework to understand the links between personality and health drawing on current theorising in the biology, evolution, and neuroscience of personality. I identify traits (i.e., alexithymia, Type D, hypochondriasis, and empathy) that are of particular concern to health psychology and set these within evolutionary cost-benefit analysis. The literature is reviewed within a three-level hierarchical model (individual, group, and organisational) and it is argued that health psychology needs to move from its traditional focus on the individual level to engage group and organisational levels.

Individual differences in temperament and behavioral management practices for nonhuman primates

Effective behavioral management plans are tailored to unique behavioral patterns of each individual species. However, even within a species behavioral needs of individuals can vary. Factors such as age, sex, and temperament can affect behavioral needs of individuals. While some of these factors, such as age and sex, are taken into account, other factors, such as an individual's temperament, are rarely specifically provided for in behavioral management plans. However, temperament may affect how animals respond to socialization, positive reinforcement training and other forms of enrichment. This review will examine how individual differences in temperament might affect, or be affected by, behavioral management practices for captive primates. Measuring temperament may help us predict outcome of social introductions. It can also predict which animals may be difficult to train using traditional methods. Further, knowledge of temperament may be able to help identify individuals at risk for development of behavioral problems. Taken together, understanding individual differences in temperament of captive primates can help guide behavioral management decisions.

Rhesus macaques (Macaca mulatta) as living fossils of hominoid personality and subjective well-being

Personality dimensions capturing individual differences in behavior, cognition, and affect have been described in several species, including humans, chimpanzees, and orangutans. However, comparisons between species are limited by the use of different questionnaires. We asked raters to assess free-ranging rhesus macaques at two time points on personality and subjective well-being questionnaires used earlier to rate chimpanzees and orangutans. Principal-components analysis yielded domains we labeled Confidence, Friendliness, Dominance, Anxiety, Openness, and Activity. The presence of Openness in rhesus macaques suggests it is an ancestral characteristic. The absence of Conscientiousness suggests it is a derived characteristic in African apes. Higher Confidence and Friendliness, and lower Anxiety were prospectively related to subjective well-being, indicating that the connection between personality and subjective well-being in humans, chimpanzees, and orangutans is ancestral in catarrhine primates. As demonstrated here, each additional species studied adds another fold to the rich, historical story of primate personality evolution.

The costs of dominance: testosterone, cortisol and intestinal parasites in wild male chimpanzees

BACKGROUND

Male members of primate species that form multi-male groups typically invest considerable effort into attaining and maintaining high dominance rank. Aggressive behaviors are frequently employed to acquire and maintain dominance status, and testosterone has been considered the quintessential physiological moderator of such behaviors. Testosterone can alter both neurological and musculoskeletal functions that may potentiate pre-existing patterns of aggression. However, elevated testosterone levels impose several costs, including increased metabolic rates and immunosuppression. Cortisol also limits immune and reproductive functions.

METHODS

To improve understanding of the relationships between dominance rank, hormones and infection status in nonhuman primates, we collected and analyzed 67 fecal samples from 22 wild adult male chimpanzees (Pan troglodytes schweinfurthii) at Ngogo, Kibale National Park, Uganda. Samples were analyzed for cortisol and testosterone levels as well as intestinal parasite prevalence and richness. 1,700 hours of observation data were used to determine dominance rank of each animal. We hypothesized that dominance rank would be directly associated with fecal testosterone and cortisol levels and intestinal parasite burden.

RESULTS

Fecal testosterone (but not cortisol) levels were directly associated with dominance rank, and both testosterone and cortisol were directly associated with intestinal parasite richness (number of unique species recovered). Dominance rank was directly associated with helminth (but not protozoan) parasite richness, so that high ranking animals had higher testosterone levels and greater helminth burden.

CONCLUSIONS

One preliminary interpretation is that the antagonist pleiotropic effects of androgens and glucocorticoids place a cost on attaining and maintaining high dominance rank in this species. Because of the costs associated with elevated steroid levels, dominance status may be an honest signal of survivorship against helminth parasites.

Personality in nonhuman primates: a review and evaluation of past research

Scientific reports of personality in nonhuman primates are now appearing with increasing frequency across a wide range of disciplines, including psychology, anthropology, endocrinology, and zoo management. To identify general patterns of research and summarize the major findings to date, we present a comprehensive review of the literature, allowing us to pinpoint the major gaps in knowledge and determine what research challenges lay ahead. An exhaustive search of five scientific databases identified 210 relevant research reports. These articles began to appear in the 1930s, but it was not until the 1980s that research on primate personality began to gather pace, with more than 100 articles published in the last decade. Our analyses of the literature indicate that some domains (e.g., sex, age, rearing conditions) are more evenly represented in the literature than are others (e.g., species, research location). Studies examining personality structure (e.g., with factor analysis) have identified personality dimensions that can be divided into 14 broad categories, with Sociability, Confidence/Aggression, and Fearfulness receiving the most research attention. Analyses of the findings pertaining to inter-rater agreement, internal consistency, test-retest reliability, generally support not only the reliability of primate personality ratings scales but also point to the need for more psychometric studies and greater consistency in how the analyses are reported. When measured at the level of broad dimensions, Extraversion and Dominance generally demonstrated the highest levels of inter-rater reliability, with weaker findings for the dimensions of Agreeableness, Emotionality, and Conscientiousness. Few studies provided data with regard to convergent and discriminant validity; Excitability and Dominance demonstrated the strongest validity coefficients when validated against relevant behavioral criterion measures. Overall, the validity data present a somewhat mixed picture, suggesting that high levels of validity are attainable, but by no means guaranteed. Discussion focuses on delineating major theoretical and empirical questions facing research and practice in primate personality.

Animal-based welfare monitoring: using keeper ratings as an assessment tool

Zoological institutions are in urgent need of identifying and implementing welfare assessment tools that allow for ongoing, quantitative monitoring of individual animal well-being. Although the American Zoological Association's (AZA) Animal Welfare Committee (AWC) promotes the use of such tools in internal review processes, current approaches to institutional welfare assessment are resource-based and outline the resources, environmental parameters and "best practices" recommended for promoting good welfare in a species in general. We highlight the value of incorporating animal-based monitoring tools that capture the individual animal's perspective and subjective experiences, including positive events and feelings, by validating zookeepers' qualitative assessments. We present evidence that, across a variety of species, caretakers' assessments of traits related to the well-being of individual animals can be both reliable and valid. Furthermore, we demonstrate that among researchers investigating the welfare of farm, laboratory, companion and even zoo animals, support already exists for developing and validating instruments that objectively evaluate the qualitative assessments of caretakers. Finally, we outline a process currently being evaluated at Brookfield Zoo for developing, validating and testing a cost-effective, user-friendly monitoring tool that will help to quantify keepers' qualitative assessments of individual well-being and can be integrated into daily operations. This tool (i.e. species-specific Welfare Score Sheets designed through consultation with animal experts) will result in weekly scores of individual well-being that are expected to provide a first indicator of welfare issues in the collection. Specifically, scores can be reviewed during regular workgroup meetings to identify welfare issues proactively, to assess whether particular conditions, practices or events impact individual well-being, and finally, to evaluate the effectiveness of efforts to address welfare issues. Upon completion of the tool validation and testing phases, we plan to make the Welfare Score Sheets for our 12 study species available to other institutions, and the methods we applied may serve as a "blueprint" for creating similar tools for additional species and institutions.

Social stress desensitizes lymphocytes to regulation by endogenous glucocorticoids: insights from in vivo cell trafficking dynamics in rhesus macaques

OBJECTIVE

To determine whether chronic social stress can desensitize leukocytes to normal physiologic regulation by endogenous glucocorticoids.

METHODS

We analyzed the longitudinal relationship between plasma cortisol levels and peripheral blood lymphocyte counts over 16 monthly assessments in 18 rhesus macaques randomized to recurrent social encounters with a stable set of conspecifics or continually varying social partners (unstable socialization).

RESULTS

Animals socialized under stable conditions showed the expected inverse relationship between plasma cortisol concentrations and circulating lymphocyte frequencies. That relationship was significantly attenuated in animals subject to unstable social conditions. Differences in leukocyte redistributional sensitivity to endogenous glucocorticoids emerged within the first week of differential socialization, persisted throughout the 60-week study period, and were correlated with other measures of glucocorticoid desensitization (blunted hypothalamic-pituitary-adrenal (HPA) axis response to acute stress and redistributional response to dexamethasone challenge). Effects of unstable social conditions on leukocyte sensitivity to cortisol regulation were not related to physical aggression.

CONCLUSION

Chronic social stress can impair normal physiologic regulation of leukocyte function by the HPA axis in ways that may contribute to the increased physical health risks associated with social adversity.

Bridging human and animal research: a comparative approach to studies of personality and health

This article evaluates a comparative approach to personality and health research. We (1) review evidence showing that personality exists and can be measured in animals, (2) illustrate the benefits of animal studies for human personality research, (3) illustrate the benefits of human studies for animal personality research, and (4) provide guidelines for making cross-species comparisons. We conclude that a comparative approach can provide unique insights into personality psychology, especially into research on personality, immunity, and health.

The multiple linkages of personality and disease

Associations between personality and health and longevity are increasingly well documented, but the causal inter-connections are often much more complex than originally anticipated. Multiple causal pathways may operate simultaneously as the individual travels an idiosyncratic route across the life-span. Therefore, a straightforward model of personality, immunity, and disease may never be established and validated, because it overlooks other key elements of the causal processes. Psychoneuroimmunology research may profit from closer integration into the broader conceptual understandings of personality and health, using a new life-span epidemiological personality approach.

Personality and serotonin transporter genotype interact with social context to affect immunity and viral set-point in simian immunodeficiency virus disease

From the beginning of the AIDS epidemic, stress has been a suspected contributor to the wide variation seen in disease progression, and some evidence supports this idea. Not all individuals respond to a stressor in the same way, however, and little is known about the biological mechanisms by which variations in individuals' responses to their environment affect disease-relevant immunologic processes. Using the simian immunodeficiency virus/rhesus macaque model of AIDS, we explored how personality (Sociability) and genotype (serotonin transporter promoter) independently interact with social context (Stable or Unstable social conditions) to influence behavioral expression, plasma cortisol concentrations, SIV-specific IgG, and expression of genes associated with Type I interferon early in infection. SIV viral RNA set-point was strongly and negatively correlated with survival as expected. Set-point was also associated with expression of interferon-stimulated genes, with CXCR3 expression, and with SIV-specific IgG titers. Poorer immune responses, in turn, were associated with display of sustained aggression and submission. Personality and genotype acted independently as well as in interaction with social condition to affect behavioral responses. Together, the data support an "interactionist" perspective [Eysenck, H.J., 1991. Personality, stress and disease: an interactionist perspective. Psychol. Inquiry 2, 221-232] on disease. Given that an important goal of HIV treatment is to maintain viral set-point as low as possible, our data suggest that supplementing anti-retroviral therapy with behavioral or pharmacologic modulation of other aspects of an organism's functioning might prolong survival, particularly among individuals living under conditions of threat or uncertainty.

Social temperament and lymph node innervation

Socially inhibited individuals show increased vulnerability to viral infections, and this has been linked to increased activity of the sympathetic nervous system (SNS). To determine whether structural alterations in SNS innervation of lymphoid tissue might contribute to these effects, we assayed the density of catecholaminergic nerve fibers in 13 lymph nodes from seven healthy adult rhesus macaques that showed stable individual differences in propensity to socially affiliate (Sociability). Tissues from Low Sociable animals showed a 2.8-fold greater density of catecholaminergic innervation relative to tissues from High Sociable animals, and this was associated with a 2.3-fold greater expression of nerve growth factor (NGF) mRNA, suggesting a molecular mechanism for observed differences. Low Sociable animals also showed alterations in lymph node expression of the immunoregulatory cytokine genes IFNG and IL4, and lower secondary IgG responses to tetanus vaccination. These findings are consistent with the hypothesis that structural differences in lymphoid tissue innervation might potentially contribute to relationships between social temperament and immunobiology.

Psychosocial influences on immunity, including effects on immune maturation and senescence

Studies investigating the influence of psychosocial factors on immunity played a critical and formative role in the field of psychoneuroimmunology (PNI), and have been a major component of articles published in Brain, Behavior and Immunity (BBI). An analysis of papers during the first two decades of BBI from 1987-2006 revealed three behavior-related topics were most prominent: (1) stress-induced changes in immune responses, (2) immune correlates of psychopathology and personality, and (3) behavioral conditioning of immunity. Important subthemes included the effect of early rearing conditions on immune maturation in the developing infant and, subsequently, psychosocial influences affecting the decline of immunity in the senescent host. The responsiveness of cell functioning in the young and elderly helped to validate the view that our immune competence is malleable. Many technical advances in immune methods were also evident. Initially, there was a greater reliance on in vitro proliferative and cytolytic assays, while later studies were more likely to use cell subset enumerations, cytokine quantification, and indices of latent virus reactivation. The reach of PNI extended from the traditional clinical entities of infection, autoimmunity, and cancer to attain a broader relevance to inflammatory physiology, and thus to asthma, cardiovascular and gastrointestinal disease. There continue to be many theoretical and applied ramifications of these seminal findings. Fortunately, the initial controversies about whether psychological processes could really impinge upon and modify immune responses have now receded into the pages of history under the weight of the empirical evidence.

Integrating animal temperament within ecology and evolution

Temperament describes the idea that individual behavioural differences are repeatable over time and across situations. This common phenomenon covers numerous traits, such as aggressiveness, avoidance of novelty, willingness to take risks, exploration, and sociality. The study of temperament is central to animal psychology, behavioural genetics, pharmacology, and animal husbandry, but relatively few studies have examined the ecology and evolution of temperament traits. This situation is surprising, given that temperament is likely to exert an important influence on many aspects of animal ecology and evolution, and that individual variation in temperament appears to be pervasive amongst animal species. Possible explanations for this neglect of temperament include a perceived irrelevance, an insufficient understanding of the link between temperament traits and fitness, and a lack of coherence in terminology with similar traits often given different names, or different traits given the same name. We propose that temperament can and should be studied within an evolutionary ecology framework and provide a terminology that could be used as a working tool for ecological studies of temperament. Our terminology includes five major temperament trait categories: shyness-boldness, exploration-avoidance, activity, sociability and aggressiveness. This terminology does not make inferences regarding underlying dispositions or psychological processes, which may have restrained ecologists and evolutionary biologists from working on these traits. We present extensive literature reviews that demonstrate that temperament traits are heritable, and linked to fitness and to several other traits of importance to ecology and evolution. Furthermore, we describe ecologically relevant measurement methods and point to several ecological and evolutionary topics that would benefit from considering temperament, such as phenotypic plasticity, conservation biology, population sampling, and invasion biology.

Twenty years of psychoneuroimmunology and viral infections in Brain, Behavior, and Immunity

For 20 years, Brain, Behavior, and Immunity has provided an important venue for the publication of studies in psychoneuroimmunology. During this time period, psychoneuroimmunology has matured into an important multidisciplinary science that has contributed significantly to our knowledge of mind, brain, and body interactions. This review will not only focus on the primary research papers dealing with psychoneuroimmunology, viral infections, and anti-viral vaccine responses in humans and animal models that have appeared on the pages of Brain, Behavior, and Immunity during the past 20 years, but will also outline a variety of strategies that could be used for expanding our understanding of the neuroimmune-viral pathogen relationship.

Adrenergic inhibition of innate anti-viral response: PKA blockade of Type I interferon gene transcription mediates catecholamine support for HIV-1 replication

Type I interferons (IFN-alpha and -beta) play a key role in anti-viral immunity, and we sought to define the molecular mechanisms by which the sympathetic nervous system (SNS) inhibits their effects. In peripheral blood leukocytes and plasmacytoid dendritic cells (pDC2), induction of interferon anti-viral activity by double-stranded RNA (poly-I:C) or CpG DNA was substantially inhibited by norepinephrine and by pharmacologic activation of the cAMP/PKA signaling pathway. This effect was specific to Type I interferons and driven by PKA-mediated repression of IFNA and IFNB gene transcription. Luciferase reporter analyses identified tandem interferon response factor-binding sites in positive regulatory domains I and III of the IFNB promoter as a key target of PKA inhibition. PKA suppression of Type I interferons was associated with impaired transcription of interferon response genes supporting the "anti-viral state", and was sufficient to account for norepinephrine-induced enhancement of HIV-1 replication. Given the ubiquitous role of Type I interferons in containing viral replication, PKA-mediated inhibition of IFN transcription could explain the stimulatory effects of catecholamines on a broad range of viral pathogens.