Mouse Social Network Dynamics and Community Structure are Associated with Plasticity-Related Brain Gene Expression.

Animal personality

The dorsal medial prefrontal cortex and basolateral amygdala exhibit social behavior-relevant neuronal oscillations, representing unified pathophysiological mechanisms underlying social behavioral deficits.

Understanding the regulatory architecture of phenotypic variation is a fundamental goal in biology, but connections between gene regulatory network (GRN) activity and individual differences in behavior are poorly understood. We characterized the molecular basis of behavioral plasticity in queenless honey bee (Apis mellifera) colonies, where individuals engage in both reproductive and non-reproductive behaviors. Using high-throughput behavioral tracking, we discovered these colonies contain a continuum of phenotypes, with some individuals specialized for either egg-laying or foraging and 'generalists' that perform both. Brain gene expression and chromatin accessibility profiles were correlated with behavioral variation, with generalists intermediate in behavior and molecular profiles. Models of brain GRNs constructed for individuals revealed that transcription factor (TF) activity was highly predictive of behavior, and behavior-associated regulatory regions had more TF motifs. These results provide new insights into the important role played by brain GRN plasticity in the regulation of behavior, with implications for social evolution.

Adolescence is an important developmental period for learning who can and cannot be trusted, and how to adapt one’s trust behavior in response to others’ reciprocal behavior. The main objective of this thesis was to create more insight into the development of adolescent trust behavior and to explain individual differences in trust behavior and the related neural activity. The development of initial trust behavior and the development of adaptive trust behavior were investigated. Furthermore, in the chapters described in this thesis, factors within the individual, e.g., gender, personality traits, symptoms of psychopathology, and perspective-taking abilities, and factors from one’s social environment, e.g., social embeddedness within social networks, were used to predict individual differences in trust behavior. Collectively, the results presented in this thesis indicate that adolescence is an important developmental period for trust behavior. First, increased levels of initial trust behavior were found throughout adolescence. Second, adolescents showed stronger adaptive trust behavior with age when interacting with untrustworthy others, and they showed age-related increases in average trust behavior when the partner behaved in a trustworthy manner. This suggests that learning who can be trusted and responding adaptively to the partner develops throughout adolescence. Adaptive trust behavior was also elicited by contextual factors, as adolescents showed they were able to overcome incorrect prior expectations about the partner and adjust their trust behavior in response to the partner’s actual behavior. The increased dlPFC and superior parietal gyrus activity that was found when interacting with this partner might tentatively suggest that cognitive control processes underlie these adaptive trust behavior processes. Furthermore, the results of this thesis indicated no support for a relationship between trust behavior and personality traits, symptoms of psychopathology, and perspective-taking abilities. The results did show that individual differences in adolescent trust behavior and the related neural activity can be explained by gender and the position within a social network. Boys showed a stronger developmental increase in initial trust behavior throughout adolescence compared to girls. Furthermore, the centrality of one´s social network position was positively related to levels of initial trust and to caudate activity, tentatively indicating increased expectancy violation when interacting with untrustworthy others.

Oxytocin receptors modulate a social salience neural network in male prairie voles

But they do! In ethology individual differences in behaviour have traditionally been ignored, treated as white noise (Ringler 1983) or, as Arak (1984) points out, considered to be maladaptive deviations from optimal strategies. Many classical ethology textbooks proceed with the implicit assumption that intraspecific differences in behaviour are less important and less interesting than differences between species. Fish behaviour, where most students begin by looking at the stereotyped response of the breeding male stickleback (Gasterosteus aculeatus) to things coloured red (Tinbergen 1951), is no exception. Closer inspection, however, reveals pronounced individual differences in the rate at which male sticklebacks attack red dummies (Rowland 1982).

Resting metabolic rate (RMR) is highly variable between individuals within a single species and the relationship between body mass and RMR does not wholly explain this variability. One factor that could account for a portion of the residual variation is animal personality or consistent individual differences (CIDs) in behaviour, but no study has examined this relationship in a free-living population of mammals. In this paper, we test for a relationship between RMR and CIDs in activity in live-trapped meadow voles Microtus pennsylvanicus after controlling for the effect of body mass. We quantified the activity levels of voles both in an unfamiliar environment and for the first 2 min in the metabolic apparatus, and then measured RMR using open-flow respirometry. As expected, there was a linear relationship between RMR and body mass, and we found strong evidence for repeatable differences in activity levels between individuals. However, contrary to the hypothesis, we did not identify a significant correlation between CIDs in behaviour and RMR after controlling for body mass. Our results suggest that, at least within species, higher activity levels may not require a greater investment in energetically demanding tissues or increased capacity for processing of energy. Alternatively, if a relationship exists, our inability to detect it may reflect a weak behavioural signal in noisy RMR data that are influenced by many factors. Our results could also reflect an artefact of individual responses to stress or a sampling bias towards more exploratory individuals in animals captured by live-trapping.

Consistent individual differences in parenting are widespread; however, we know little about why there is variation in parenting behavior among individuals within species. One possible explanation for consistent individual differences in parenting is that individuals invest in different aspects of parental care, such as provisioning or defense. In this field study we measured consistent individual differences in parenting behavior and evaluated correlations between parenting and other behaviors in threespine stickleback (Gasterosteus aculeatus). We repeatedly measured male parenting behavior and male behavior in the presence of three different types of live intruders: a female, a conspecific male, and a predator, meant to provoke courtship, aggressive and antipredator behavior, respectively. While males plastically adjusted their reactions to different types of intruders, we found consistent individual differences in behavior (behavioral types) both within and across contexts, even after accounting for variation in body size and nest characteristics. Males that performed more parenting behavior responded faster to all types of intruders. These results suggest that in nature, individual male stickleback exhibit robust parental behavioral types, and highly parental males are more attentive to their surroundings. Future studies are needed to examine the potential causes of individual variation in parental behavior in the field.

Fish play an important role in the culture of Japan, supplying the primary source of food protein. Research on fish ecology in Japan began developing about 1955, and paralleled that in North America and Europe, but has a number of unique differences. Two main research foci, stream fish ecology and ecology of Lake Biwa, were founded by H. Kawanabe and his colleagues while graduate students in D. Miyadi’s laboratory at Kyoto University in the 1950s. The focus on studies of individual differences in ecology, life history, and behavior by direct observation that were developed in this laboratory had a pervasive influence on research that has continued to the present. In the 1980s, Kawanabe, who had succeeded Miyadi as laboratory head, also co-organized a major research project on the complex communities of cichlid fishes in Lake Tanganyika, which has involved nearly every major Japanese investigator in fish ecology since. A review of research conducted by Japanese investigators in stream fish ecology, ecology of fishes in lakes Biwa and Tanganyika, and marine reef fish ecology revealed a wealth of literature of which most English-speaking fish ecologists are unaware. The most striking difference between Western and Japanese research is the focus on detailed observations and experiments in natural habitats of individual differences in behavior, life history, and ecology, and how these ultimately affect processes at the population and community level, as amply demonstrated by Kawanabe’s early work on ayu, Plecoglossus altivelis. This approach predated by 20–30 years the current interest in individual differences and individual-based models in North America and Europe.

In recent years, animal social interactions have received much attention in terms of personality research (e.g. aggressive or cooperative interactions). However, other components of social behaviour such as those describing the intensity, frequency, directedness and individual repeatability of interactions in animal groups have largely been neglected. Network analysis offers a valuable opportunity to characterize individual consistency of traits in labile social groups and therein provide novel insights to personality research in ways previously not possible using traditional techniques. Should individual network positions be consistently different between individuals under changing conditions, they might reflect expressions of an individual's personality. Here, we discuss a conceptual framework for using network analyses to infer the presence of individual differences and present a statistical test based on randomization techniques for testing the consistency of network positions in individuals. The statistical tools presented are useful because if particular individuals consistently occupy key positions in social networks, then this is also likely to have consequences for their fitness as well as for that of others in the population. These consequences may be particularly significant since individual network position has been shown to be important for the transmission of diseases, socially learnt information and genetic material between individuals and populations.

Children's self-imposed isolation in the company of others (social withdrawal due to shyness or unsociability) and active isolation due to direct aggressive behaviors can challenge successful engagement in the peer group. The developmental attributional perspective acknowledges that children's intended affiliative responses are, in part, guided by their emotions and beliefs toward peers' social behaviors and may differ depending on children's sex, age group, and social behavior. This study aimed to (1) describe preschoolers' beliefs, emotions, and intended affiliative preferences toward aggressive, shy, and unsociable peers, depending on children's sex and age group, and (2) explore the associations between preschoolers' beliefs, emotions and intended affiliative preferences, depending on children's social behaviors and children's sex or age group. A total of 158 preschoolers aged 3-6 years were interviewed, using the Child Attributions Interview to assess their beliefs, emotions and intended affiliative preferences toward peers. Teachers completed the Social Competence and Behavior Evaluation Scale to assess children's prosocial behaviors, aggressive-anger, and anxious-withdrawal. Preschoolers' perspectives toward shy and unsociable peers were less negative than toward aggressive peers. However, participants in our sample were not fully aware of the different intentionality and social motivations of shy and unsociable peers. Higher levels of perceived social standing, social motivation and sympathy predicted higher affiliative preferences toward shy, unsociable, and aggressive peers. However, the magnitude of the associations between preschoolers' beliefs, emotions and intended affiliative preferences differed, depending on children's sex, age group and prosocial behavior, especially toward aggressive and shy peer behaviors. These findings are in line with the developmental attributional perspective, but highlight the need to account for developmental specificities, sex differences in peer relationships and children's individual differences in social behaviors.

Despite the growing evidence for the importance of developmental experiences shaping consistent individual differences in behaviour and physiology, the role of endocrine factors underlying the development and maintenance of such differences across multiple traits, remains poorly understood. Here, we investigated how an experimental manipulation of circulating glucocorticoids during early adolescence affects behavioural and physiological variation and covariation later in life in the precocial cavy (Cavia aperea). Plasma cortisol concentrations were experimentally elevated by administering cortisol via food for 3 weeks. Struggle docility, escape latency, boldness, exploration and social behaviour were then tested three times after individuals attained sexual maturity. In addition, blood samples were taken repeatedly to monitor circulating cortisol concentrations. Exogenous cortisol affected mean trait expression of plasma cortisol levels, struggle docility and escape latency. Repeatability of cortisol and escape latency was increased and repeatability of struggle docility tended to be higher (approaching significance) in treated individuals. Increased repeatability was mainly caused by an increase of among-individual variance. Correlations among docility, escape latency and cortisol were stronger in treated animals compared to control animals. These results suggest that exposure to elevated levels of cortisol during adolescence can alter animal personality traits as well as behavioural syndromes. Social and risk-taking traits showed no correlation with cortisol levels and were unaffected by the experimental manipulation, indicating behavioural modularity. Taken together, our data highlight that cortisol can have organising effects during adolescence on the development of personality traits and behavioural syndromes, adding to the increasing evidence that not only early life but also adolescence is an important sensitive period for behavioural development.

Thyroid hormone regulation by stress and behavioral differences in adult male rats

Although individual differences in the behavior of animals, sometimes referred to as personality, have recently received considerable attention, the development of such differences remains understudied. We previously found consistent individual differences in behavior in four tests simulating everyday contexts in 74 preweaning age kittens from 16 litters of the domestic cat. To study the development of consistent among-individual differences in four behavioral traits in cats, we followed a subset of these same individuals and repeated the same tests at 6 and 12 months of age. Some individual differences in behavior became increasingly repeatable with age due to a combination of decreased individual-level variance (canalization) and increased among-individual variance; these changes in variance and repeatability continued into adulthood (12 months). We did not observe behavioral syndromes at any age, in contrast to our previous reports in a different population of adult cats. The mechanisms that underlie increased repeatability with age and the possibility of personality structure differing between populations in this species remain to be studied.

Some like it varied: Individual differences in preference for feed variety in dairy heifers