Primates got personality,too: Toward an integrative primatology of consistent individual differences in behavior

In recent years, research on animal personality has exploded within the field of behavioral ecology. Consistent individual differences in behavior exist in a wide range of species, and these differences can have fitness consequences and influence several aspects of a species' ecology. In comparison to studies of other animals, however, there has been relatively little research on the behavioral ecology of primate personality. This is surprising given the large body of research within psychology and biomedicine showing that primate personality traits are heritable and linked to health and life history outcomes. In this article, I bring together theoretical perspectives on the ecology and evolution of animal personality with an integrative review of what we know about primate personality from studies conducted on captive, free‐ranging, and wild primates. Incorporating frameworks that emphasize consistency in behavior into primate behavioral ecology research holds promise for improving our understanding of primate behavioral evolution.     

Effects of breed,sex, and neuter status on trainability in dogs

Abstract

In a previous study of canine temperament (Hsu and Serpell 2003), a distinct “trainability” factor was identified, characterized by a dog's willingness to attend to its owner and obey simple commands, combined with a high “fetch” motivation, and low levels of distractibility and/or resistance to correction. This paper explores the distribution of this trait in a large sample of dogs in relation to breed, sex and neuter status. The owners of 1,563 dogs belonging to 11 common breeds were invited to assess them for “trainability” using a standardized questionnaire (C-BARQ^©). Highly significant breed differences in trainability were detected. In two breeds with distinct field and show bred lines, show bred dogs obtained significantly lower trainability scores. Although no overall sex differences in trainability were detected, male Dachshunds and West Highland White Terriers were found to be significantly more trainable than females. Neutering was not associated with any differences in trainability in female dogs in any breed, but was associated with positive effects on trainability in male Shetland sheepdogs. The findings suggest that there is scope for improving trainability in most breeds of dog, and emphasize the dangers of generalizing among breeds with respect to sex differences in trainability or the benefits of neutering. The biological basis of the trainability trait is also discussed in light of recent research on the evolution of canine social cognition.     

The role of temperament in the relationship between morningness–eveningness and mood

Apart from differences in circadian phase position, individuals with different morningness–eveningness levels vary in many more characteristics. Particularly consistent relationships have been observed between morningness–eveningness and mood. Eveningness has been associated with disadvantageous mood, e.g. depressiveness in healthy individuals, and mood disorders. A concept of social jetlag suggests that evening subjects function in less advantageous environments due to discrepancies between internal and social time (societies promote morning-oriented functioning), which results in their lowered mood. Individual temperament, as defined by the Regulative Theory of Temperament (RTT), refers to the capacity of the human organism to meet environmental requirements – the greater the capacity, the less negative impact of external conditions. Thus, the aim of this study is to determine which RTT traits are linked to both morningness–eveningness and mood dimensions and to test whether they account for the relationship between morningness–eveningness and mood. A sample of 386 university students (267 female) aged between 19 and 47 (M?=?21.15, SD?=?4.23) years completed the University of Wales Institute of Science and Technology (UWIST) Mood Adjective Check List, Morningness–Eveningness Questionnaire and Formal Characteristics of Behaviour – Temperament Inventory. Analyses revealed lower endurance (EN) and higher emotional reactivity (ER) related to eveningness as well as to lower hedonic tone (HT), energetic arousal (EA) and to higher tense arousal (TA). Moreover, eveningness was associated with lower HT, EA and higher TA. Among RTT traits, EN was most strongly related to eveningness, and mediation analyses revealed that this temperamental trait fully mediated the relationship between eveningness and the three mood dimensions. The remaining RTT traits did not provide more explanation of the association between morningness–eveningness and mood than EN itself. If subjects did not differ in EN, the association between morningness–eveningness and mood was absent. EN is discussed as a protective factor against negative consequences of social jetlag and particularly lowered mood in evening individuals.     

Blood Parasite Infection Intensity Covaries with Risk‐Taking Personality in Male Carpetan Rock Lizards (Iberolacerta cyreni)

Identifying evolutionary and developmental mechanisms underlying consistent between‐individual differences in behaviour is the main goal in ‘animal personality studies’. Here, we explored whether activity and risk‐taking varied consistently between individuals and correlated to various – potentially fitness linked – male traits in Carpetan rock lizards (Iberolacerta cyreni). Lizards showed significant consistency within both behaviours, implying the presence of activity and risk‐taking personalities. However, there were no correlation between activity and risk‐taking, neither on the between‐ nor on the within‐individual levels, implying the absence of a behavioural syndrome. We found a strong link between the intensity of blood parasite (Haemogregarinidae) infection and risk‐taking: lizards with higher infection intensity took more risk. While we cannot distinguish cause from causative in the parasite intensity – risk‐taking correlation – our results are in line with the asset protection hypothesis predicting that individuals with lower future reproductive value should focus on the current reproductive event and take higher risk.     

A genomic prediction model for racecourse starts in the Thoroughbred horse

Durability traits in Thoroughbred horses are heritable, economically valuable and may affect horse welfare. The aims of this study were to test the hypotheses that (i) durability traits are heritable and (ii) genetic data may be used to predict a horse's potential to have a racecourse start. Heritability for the phenotype ‘number of 2‐ and 3‐year‐old starts’ was estimated to be  = 0.11 ± 0.02 (n = 4499). A genome‐wide association study identified SNP contributions to the trait. The neurotrimin (NTM), opioid‐binding protein/cell adhesion molecule like (OPCML) and prolylcarboxypeptidase (PRCP) genes were identified as candidate genes associated with the trait. NTM functions in brain development and has been shown to have been selected during the domestication of the horse. PRCP is an established expression quantitative trait locus involved in the interaction between voluntary exercise and body composition in mice. We hypothesise that variation at these loci contributes to the motivation of the horse to exercise, which may influence its response to the demands of the training and racing environment. A random forest with mixed effects (RFME) model identified a set of SNPs that contributed to 24.7% of the heritable variation in the trait. In an independent validation set (n = 528 horses), the cohort with high genetic potential for a racecourse start had significantly fewer unraced horses (16% unraced) than did low (27% unraced) potential horses and had more favourable race outcomes among those that raced. Therefore, the information from SNPs included in the model may be used to predict horses with a greater chance of a racecourse start.     

An approach to canine behavioural genetics employing guide dogs for the blind

The purpose of this study was to attempt to find related variables of the canine genome with behavioural traits of dogs maintained and tested in a guide dog facility which provided a relatively uniform environment. The study involved 81 Labrador Retrievers that were being trained as guide dogs. Each dog was taken on walk-out sessions in which the trainer weekly recorded observations that were related to behavioural traits. The records were subjected to key-word analysis of 14 behaviour-related words. A factor analysis on the appearance rate of the 14 key words or phrases resulted in the extraction of six factors that accounted for 67.4% of the variance. Factor 1, referred to as aggressiveness, was significantly related to the success or failure of the dog in qualifying as a guide dog, and was also related to the variable of litter identification. Factor 2, referred to as distraction, was related to the variable of trainer. Factor 3, activity level, was related to the variable of sex, and was significantly related to the polymorphisms of c.471T>C in the solute carrier family 1 ( neuronal/epithelial high affinity glutamate transporter ) member 2 gene and c.216G>A in the catechol-O-methyltransferase gene. The involvement of polymorphisms c.471T>C and c.216G>A in behavioural patterns related to activity level is similar to comparable genetic studies in other mammalian species. These results contribute to a greater understanding of the role of these genes in behaviour.     

Are atypical depression,borderline personality disorder and bipolar II disorder overlapping manifestations of a common cyclothymic diathesis?

The constructs of atypical depression, bipolar II disorder and borderline personality disorder (BPD) overlap. We explored the relationships between these constructs and their temperamental underpinnings. We examined 107 consecutive patients who met DSM-IV criteria for major depressive episode with atypical features. Those who also met the DSM-IV criteria for BPD (BPD+), compared with those who did not (BPD-), had a significantly higher lifetime comorbidity for body dysmorphic disorder, bulimia nervosa, narcissistic, dependent and avoidant personality disorders, and cyclothymia. BPD+ also scored higher on the Atypical Depression Diagnostic Scale items of mood reactivity, interpersonal sensitivity, functional impairment, avoidance of relationships, other rejection avoidance, and on the Hopkins Symptoms Check List obsessive-compulsive, interpersonal sensitivity, anxiety, anger-hostility, paranoid ideation and psychoticism factors. Logistic regression revealed that cyclothymic temperament accounted for much of the relationship between atypical depression and BPD, predicting 6 of 9 of the defining DSM-IV attributes of the latter. Trait mood lability (among BPD patients) and interpersonal sensitivity (among atypical depressive patients) appear to be related as part of an underlying cyclothymic temperamental matrix.     

Small within-day increases in temperature affects boldness and alters personality in coral reef fish

Consistent individual differences in behaviour, termed personality, are common in animal populations and can constrain their responses to ecological and environmental variation, such as temperature. Here, we show for the first time that normal within-daytime fluctuations in temperature of less than 3°C have large effects on personality for two species of juvenile coral reef fish in both observational and manipulative experiments. On average, individual scores on three personality traits (PTs), activity, boldness and aggressiveness, increased from 2.5- to sixfold as a function of temperature. However, whereas most individuals became more active, aggressive and bold across temperature contexts (were plastic), others did not; this changed the individual rank order across temperatures and thus altered personality. In addition, correlations between PTs were consistent across temperature contexts, e.g. fish that were active at a given temperature also tended to be both bold and aggressive. These results (i) highlight the importance of very carefully controlling for temperature when studying behavioural variation among and within individuals and (ii) suggest that individual differences in energy metabolism may contribute to animal personality, given that temperature has large direct effects on metabolic rates in ectotherms.     

Serotonin receptor genes 5HT1A and 5HT2A modify the relation between childhood temperament and adulthood hostility

We examined a modifying role of 5HT1A and 5HT2A receptors in the relation between childhood difficult temperament and adulthood hostility in 729 subjects derived from a population-based sample. Subjects were 3–12 years when their childhood temperaments consisting of hyperactivity, low sociability and negative emotionality (i.e. the difficult temperament), were assessed by their mothers. Their adulthood hostility comprising anger, cynicism and paranoia, was measured twice, 17 and 21 years later. It was found that the 5HT1A and 5HT2A receptors were not related to childhood temperament or to adult hostility, but they modified the association between childhood hyperactivity and adult hostility in men. Male carriers of T/T genotype of 5HTR2A who were rated hyperactive by their mothers expressed a high level of hostility, especially that of cynicism, in adulthood. For men with other genetic variants, such an association was not seen. This finding was consistent across the two follow-ups 4 years apart. Further research is needed to clarify whether mother-related hyperactivity adequately describes the temperament of the child or is a reflection of mother's hostile child-rearing attitudes.