What drives adult personality development? A comparison of theoretical perspectives and empirical evidence

Increasing numbers of empirical studies provide compelling evidence that personality traits change across the entire lifespan. What initiates this continuing personality development and how does this development proceed? In this paper, we compare six theoretical perspectives that offer testable predictions about why personality develops the way it does and identify limitations and potentials of these perspectives by reviewing how they hold up against the empirical evidence. While all of these perspectives have received some empirical support, there is only little direct evidence for propositions put forward by the five-factor theory of personality and the theory of genotype→environment effects. In contrast, the neo-socioanalytic theory appears to offer a comprehensive framework that fits the empirical findings and allows the integration of other, more specialized, perspectives that focus on specific aspects of personality development like the role of time, systematic differences between categories of social roles or the active partake of the person himself or herself. We draw conclusions on the likely driving factors for adult personality development and identify avenues for future research.

Effects of thermal environment on hypothalamic-pituitary-adrenal axis hormones, oxytocin, and behavioral activity in periparturient sows

Provision of additional floor heating (33 to 34 degrees C) at birth and during the early postnatal hours is favorable for newborn piglets of domestic sows (Sus scrofa). We investigated whether this relatively high temperature influenced sow behavior and physiology around farrowing. One-half of 28 second-parity pregnant sows were randomly chosen to be exposed to floor heating 12 h after onset of nest building and until 48 h after birth of the first piglet (heat treatment), whereas the rest of the sows entered the control group (control treatment) with no floor heating. Hourly blood sampling from 8 h before and until 24 h after the birth of the first piglet was used for investigation of temporal changes in plasma concentrations of oxytocin, cortisol, and ACTH. In addition, occurrence and duration of sow postures were recorded -8 to +48 h relative to the birth of the first piglet. There was a clear temporal development in sow behavior and hormone concentrations (ACTH, cortisol, and oxytocin) across parturition (P < 0.001), independent of treatment. In general, hormone concentrations increased from the start to the end of farrowing. The observed oxytocin increase and peak late in farrowing coincided with the passive phase where sows lie laterally with an overall reduced activity. Floor heating increased the mean concentration of cortisol (P = 0.02; estimated as 29% greater than in controls) and tended to increase the mean concentration of ACTH (P = 0.08; estimated as 17% greater than in controls), but we did not find any treatment effect on mean oxytocin concentrations, the course of parturition, or the behavior of sows. Behavioral thermoregulation may, however, have lost some function for the sows because the floor was fully heated in our study. In addition, exposure to heat decreased the between-sow variation of plasma oxytocin (approximately 31% less relative to control) and ACTH (approximately 46% less relative to control). Whether this decreased variation may be indicative of acute stress or linked to other biological events is unclear. In conclusion, inescapable floor heating (around 33.5 degrees C) may be considered a stressor for sows around farrowing, giving rise to elevated plasma concentrations of cortisol, but without concurrent changes in oxytocin or behavioral activity.

Effects, but no interactions, of ubiquitous pesticide and parasite stressors on honey bee (Apis mellifera) lifespan and behaviour in a colony environment

Interactions between pesticides and parasites are believed to be responsible for increased mortality of honey bee (Apis mellifera) colonies in the northern hemisphere. Previous efforts have employed experimental approaches using small groups under laboratory conditions to investigate influence of these stressors on honey bee physiology and behaviour, although both the colony level and field conditions play a key role for eusocial honey bees. Here, we challenged honey bee workers under in vivo colony conditions with sublethal doses of the neonicotinoid thiacloprid, the miticide tau-fluvalinate and the endoparasite Nosema ceranae, to investigate potential effects on longevity and behaviour using observation hives. In contrast to previous laboratory studies, our results do not suggest interactions among stressors, but rather lone effects of pesticides and the parasite on mortality and behaviour, respectively. These effects appear to be weak due to different outcomes at the two study sites, thereby suggesting that the role of thiacloprid, tau-fluvalinate and N. ceranae and interactions among them may have been overemphasized. In the future, investigations into the effects of honey bee stressors should prioritize the use of colonies maintained under a variety of environmental conditions in order to obtain more biologically relevant data.

From nature versus nurture, via nature and nurture, to gene x environment interaction in mental disorders

It is now generally accepted that complex mental disorders are the results of interplay between genetic and environmental factors. This holds out the prospect that by studying G x E interplay we can explain individual variation in vulnerability and resilience to environmental hazards in the development of mental disorders. Furthermore studying G x E findings may give insights in neurobiological mechanisms of psychiatric disorder and so improve individualized treatment and potentially prevention. In this paper, we provide an overview of the state of field with regard to G x E in mental disorders. Strategies for G x E research are introduced. G x E findings from selected mental disorders with onset in childhood or adolescence are reviewed [such as depressive disorders, attention-deficit/hyperactivity disorder (ADHD), obesity, schizophrenia and substance use disorders]. Early seminal studies provided evidence for G x E in the pathogenesis of depression implicating 5-HTTLPR, and conduct problems implicating MAOA. Since then G x E effects have been seen across a wide range of mental disorders (e.g., ADHD, anxiety, schizophrenia, substance abuse disorder) implicating a wide range of measured genes and measured environments (e.g., pre-, peri- and postnatal influences of both a physical and a social nature). To date few of these G x E effects have been sufficiently replicated. Indeed meta-analyses have raised doubts about the robustness of even the most well studied findings. In future we need larger, sufficiently powered studies that include a detailed and sophisticated characterization of both phenotype and the environmental risk.

Effects of the two production programs 'Naturafarm' and 'conventional' on the prevalence of non-perforating abomasal lesions in Swiss veal calves at slaughter

Non-perforating abomasal lesions are a considerable problem affecting more than half the population of veal calves. The objective of the present study was to assess the prevalence of pyloric and fundic abomasal lesions in Swiss veal calves at slaughter and to compare the occurrence of non-perforating abomasal lesions between two different production programs ('Naturafarm' and 'conventional'). 'Conventional'-production settings met the minimal standards as defined by the Swiss animal welfare legislation, whereas 'Naturafarm' production complied with increased animal welfare requirements. In order to identify risk factors for the development of abomasal lesions, information on management, housing, and feeding was obtained by a questionnaire. A total of 125 abomasa were randomly selected in one large abattoir. They were examined macroscopically, and the occurence of lesions in either the fundic or pyloric region of the abomasum was recorded separately. Animals raised in the 'conventional'-production setting revealed a significantly higher prevalence of lesions in the fundic part. Factors significantly affecting the prevalence of non-perforating lesions in the fundic part were the 'conventional'-production environment, including missing access to an outside pen, missing access to water and straw as the only roughage, feeding by bucket and the liquid milk by-product Protofit in combination with the powder Sprayfit.

Role of the environment in the development of canine atopic dermatitis in Labrador and golden retrievers

Canine and human atopic dermatitis are multifaceted diseases whose clinical development may be influenced by several factors, such as genetic background, environment, secondary infections, food and psychological effects. The role of the environment has been extensively examined in humans but remains unclear in dogs. The aim of this study was to examine environmental factors in two genetically close breeds, Labrador and golden retrievers. Using standard criteria, atopic dogs in Switzerland and Germany were selected and compared with healthy individuals. Information on environmental factors was collected using a 46-question survey encompassing date and place of birth, way of life at the breeder's and owner's home, food and treatments. Univariate and multivariate logistic regression were used to assess the association between potential risk factors and disease status. The following parameters were associated with an increased risk of disease development: living in a shed during puppyhood, adoption at the age of 8-12 weeks and washing the dog regularly. In contrast, the following factors were associated with a lower risk: living in a rural environment, living in a household with other animals and walking in a forest. These associations do not prove causality but support the primary hypothesis that certain environmental factors may influence the development of canine atopic dermatitis. Further studies are warranted to confirm these results and conclusions.

Regrouping rabbit does in a familiar or novel pen: Effects on agonistic behaviour, injuries and core body temperature

Regrouping female rabbits in group-housing systems is common management practice in rabbit breeding, which may, however, induce agonistic interactions resulting in social stress and severe injuries. Here we compared two methods of regrouping female rabbits with respect to their effects on behaviour, stress and injuries. Thus, we introduced two unfamiliar rabbits into a group of rabbits either in the group's familiar pen (HOME) or in a novel disinfected pen (NOVEL), and assessed the effects of these treatments on general activity, number and duration of agonistic interactions, number and severity of injuries and body temperature as a measure of stress. General activities were not affected by the method of regrouping. Also, treatment had no effect on the number and duration of agonistic interactions. However, the numbers of injuries (P=0.030) as well as body temperature on the first clay after regrouping (p=0.0036) were increased in rabbits regrouped in a novel clean pen. These findings question the recommendation to introduce unfamiliar does into established groups in a neutral environment and indicate that regrouping in the group's home pen may decrease the risk of severe injuries and social stress. (C) 2011 Elsevier B.V. All rights reserved.

Acute effects of intravenous heroin on the hypothalamic-pituitary-adrenal axis response: a controlled trial

Heroin dependence is associated with a stressful environment and with dysfunction of the hypothalamic-pituitary-adrenal (HPA) axis. The present study examined the acute effects of intravenous heroin versus placebo on the HPA axis response in heroin-dependent patients. Twenty-eight heroin-dependent patients in heroin-assisted treatment and 20 age- and sex-matched healthy participants were included in a controlled trial in which patients were twice administered heroin or saline in a crossover design, and healthy controls were only administered saline. The HPA axis response was measured by adrenocorticotropic hormone (ACTH) levels and by cortisol levels in serum and saliva before and 20 and 60 minutes after substance administration. Craving, withdrawal, and anxiety levels were measured before and 60 minutes after substance application. Plasma concentrations of heroin and its main metabolites were assessed using high-performance liquid chromatography. Heroin administration reduces craving, withdrawal, and anxiety levels and leads to significant decreases in ACTH and cortisol concentrations (P < 0.01). After heroin administration, cortisol concentrations did not differ from healthy controls, and ACTH levels were significantly lower (P < 0.01). In contrast, when patients receive saline, all hormone levels were significantly higher in patients than in healthy controls (P < 0.01). Heroin-dependent patients showed a normalized HPA axis response compared to healthy controls when they receive their regular heroin dose. These findings indicate that regular opioid administration protects addicts from stress and underscore the clinical significance of heroin-assisted treatment for heroin-dependent patients.

Species Richness-Environment Relationships of European Arthropods at Two Spatial Grains: Habitats and Countries

We study how species richness of arthropods relates to theories concerning net primary productivity, ambient energy, water-energy dynamics and spatial environmental heterogeneity. We use two datasets of arthropod richness with similar spatial extents (Scandinavia to Mediterranean), but contrasting spatial grain (local habitat and country). Samples of ground-dwelling spiders, beetles, bugs and ants were collected from 32 paired habitats at 16 locations across Europe. Species richness of these taxonomic groups was also determined for 25 European countries based on the Fauna Europaea database. We tested effects of net primary productivity (NPP), annual mean temperature (T), annual rainfall (R) and potential evapotranspiration of the coldest month (PETmin) on species richness and turnover. Spatial environmental heterogeneity within countries was considered by including the ranges of NPP, T, R and PETmin. At the local habitat grain, relationships between species richness and environmental variables differed strongly between taxa and trophic groups. However, species turnover across locations was strongly correlated with differences in T. At the country grain, species richness was significantly correlated with environmental variables from all four theories. In particular, species richness within countries increased strongly with spatial heterogeneity in T. The importance of spatial heterogeneity in T for both species turnover across locations and for species richness within countries suggests that the temperature niche is an important determinant of arthropod diversity. We suggest that, unless climatic heterogeneity is constant across sampling units, coarse-grained studies should always account for environmental heterogeneity as a predictor of arthropod species richness, just as studies with variable area of sampling units routinely consider area.

Effects of genetic and environmental factors on chronic lower airway disease in horses

BACKGROUND: Environment and genetics influence the manifestation of recurrent airway obstruction (RAO), but the associations of specific factors with mild, moderate, and severe clinical signs are unknown. HYPOTHESIS: We hypothesized that sire, feed, bedding, time outdoors, sex, and age are associated with clinical manifestations of mild, moderate, and severe lower airway disease. ANIMALS: Direct offspring of 2 RAO-affected Warmblood stallions (F1S1, n = 172; F1S2, n = 135); maternal half-siblings of F1S1 (mHSS1, n = 66); and an age-matched, randomly chosen control group (CG, n = 33). METHODS: A standardized questionnaire was used to assess potential risk factors and to establish a horse owner assessed respiratory signs index (HOARSI 1-4, from healthy to severe) according to clinical signs of lower airway disease. RESULTS: More F1S1 and F1S2 horses showed moderate to severe clinical signs (HOARSI 3 and HOARSI 4 combined, 29.6 and 27.3%, respectively) compared with CG and mHSS1 horses (9.1 and 6.2%, respectively; contingency table overall test, P < .001). Sire, hay feeding, and age (in decreasing order of strength) were associated with more severe clinical signs (higher HOARSI), more frequent coughing, and nasal discharge. CONCLUSIONS AND CLINICAL RELEVANCE: There is a genetic predisposition and lesser but also marked effects of hay feeding and age on the manifestation of moderate to severe clinical signs, most markedly on coughing frequency. In contrast, mild clinical signs were not associated with sire or hay feeding in our populations.

Effects of minor laboratory procedures, adrenalectomy, social defeat or acute alcohol on regional brain concentrations of corticosterone

Concentrations of corticosterone in brain areas of TO strain mice were measured by radioimmunoassay. The studies examined the effects of routine laboratory maneuvers, variation during the circadian peak, adrenalectomy, social defeat and acute injections of alcohol on these concentrations. Brief handling of mice increased corticosterone levels in plasma but not in striatum and reduced those in the hippocampus. Single injections of isotonic saline raised the plasma concentrations to a similar extent as the handling, but markedly elevated concentrations in the three brain regions. Five minutes exposure to a novel environment increased hippocampal and cerebral cortical corticosterone levels and striatal concentrations showed a larger rise. However, by 30 min in the novel environment, plasma concentrations rose further while those in striatum and cerebral cortex fell to control levels and hippocampal corticosterone remained elevated. Over the period of the circadian peak the hippocampal and striatal concentrations paralleled the plasma concentrations but cerebral cortical concentrations showed only small changes. Adrenalectomy reduced plasma corticosterone concentrations to below detectable levels after 48 h but corticosterone levels were only partially reduced in the hippocampus and striatum and remained unchanged in the cerebral cortex. Single or repeated social defeat increased both brain and plasma concentrations after 1 h. Acute injections of alcohol raised the regional brain levels in parallel with plasma concentrations. The results show that measurements of plasma concentrations do not necessarily reflect the levels in brain. The data also demonstrate that corticosterone levels can change differentially in specific brain regions. These results, and the residual hormone seen in the brain after adrenalectomy, are suggestive evidence for a local origin of central corticosterone.

Autonomic and cardiovascular effects of acute high altitude exposure after myocardial infarction and in normal volunteers

High sympathetic tone creates a significant risk for ventricular arrhythmias and sudden death, which can especially affect patients after a myocardial infarction (MI) when exercising in a hypoxic environment.