The molecular genetic architecture of human personality: beyond self-report questionnaires

Computer reconstruction of gene networks controlling anxiety levels in humans and laboratory mice

Anxiety is a normotypic human condition, and like any other emotion has an adaptive value. But excessively high or low anxiety has negative consequences for adaptation, which primarily determines the importance of studying these two extreme conditions. At the same time, it is known that the perception of aversive stimuli associated with anxiety leads to changes in the activity of the brain's cingulate cortex. The advantage of animals as models in studying the genetic bases of anxiety in humans is in the ability to subtly control the external conditions of formation of a certain state, the availability of brain tissues, and the ability to create and study transgenic models, including through the use of differentially expressed genes of small laboratory animals from the family Muridae with low and high anxiety. Within the framework of the translational approach, a three-domain potential gene network, which is associated with generalized anxiety in humans, was reconstructed using mouse models with different levels of anxiety by automatically analyzing the texts of scientific articles. One domain is associated with reduced anxiety in humans, the second with increased anxiety, and the third is a dispatcher who activates one of the two domains depending on the status of the organism (genetic, epigenetic, physiological). Stages of work: (I) A list of genes expressed in the cingulate cortex of the wild type CD-1 mouse line from the NCBI GEO database (experiment GSE29014). Using the tools of this database, differences in gene expression levels were revealed in groups of mice with low and high (relatively normal) anxiety. (II) Search for orthologs of DEG in humans and mice associated with anxiety in the OMA Orthology database. (III) Computer reconstruction using the ANDSystem cognitive system based on (a) human orthologous genes from stage (III), (b) human genes from the MalaCards database associated with human anxiety. The proven methods of the translational approach for the reconstruction of gene networks for behavior regulation can be used to identify molecular genetic markers of human personality traits, propensity to psychopathology.

The Moderation Role of Neuroticism for Anxiety among Burdened Dementia Caregivers: A Study on Care Giver-Recipient Dyads

Caregiving burden proves to be a risk factor of anxiety disorders and anxiety affection. The current study investigates how an endogenous personality dimension - neuroticism - moderates the association between caregiving burden and anxiety affection. Between 2015 and 2017, the study deployed a cross-sectional survey of 674 (response rate = 89%) older adults who were hospitalized for dementia at two hospitals. From all primary caregivers of these patients, 661 agreed to participate in the survey which yielded 661 matched dyads as the final sample. Caregiving burden, neuroticism, and anxiety affection were each measured by established assessment instruments. We employed multivariate OLS regression to test the moderator and regressor effects. We found that care burden is a significant risk factor of higher levels of anxiety affection (β = .17, p < .001), and accounts for 4.6% of the variance in anxiety. Neurotic personality is also significantly associated with a greater level of anxiety (β = .26, p < .001). Neurotic personality moderates the association between anxiety and care burden (β = .24, p < .001). Our findings suggest that social and healthcare workers should assess caregiver personality and burden as well as provide support, resources, and coping strategies to those with neurotic personality traits or high care burden in an effort to reduce anxiety among caregivers.

Risk-taking coping style correlates with SERT SNP290 polymorphisms in free-living great tits

The coping style of an individual in relation to potentially dangerous situations has been suggested to be inherited in a polygenic fashion, being SERT one of the candidate genes. In this paper, we assessed in free-living great tits Parus major the association between SNP290 in the SERT promoter and three standard fear-related behaviors, namely the response of the birds to a black and white flag fixed to the top of the nest-box, distress calling rate of the birds in the hand once captured and the hissing call of incubating females when approached by a predator. We found a strong association between SNP290 polymorphism and the three risk-taking behaviors, with birds with genotype CT entering faster to the nest box with the flag and displaying more distress calls and less hissing calls. CT birds could therefore be described as more proactive than CC individuals. These results also suggest that hissing behavior should be regarded as a fear-induced shy behavior, and confirm that SERT has an important function in relation to risk aversion behaviors and coping style.

From warrior genes to translational solutions: novel insights into monoamine oxidases (MAOs) and aggression

The pervasive and frequently devastating nature of aggressive behavior calls for a collective effort to understand its psychosocial and neurobiological underpinnings. Regarding the latter, diverse brain areas, neural networks, neurotransmitters, hormones, and candidate genes have been associated with antisocial and aggressive behavior in humans and animals. This review focuses on the role of monoamine oxidases (MAOs) and the genes coding for them, in the modulation of aggression. During the past 20 years, a substantial number of studies using both pharmacological and genetic approaches have linked the MAO system with aggressive and impulsive behaviors in healthy and clinical populations, including the recent discovery of MAALIN, a long noncoding RNA (lncRNA) regulating the MAO-A gene in the human brain. Here, we first provide an overview of the MAOs and their physiological functions, we then summarize recent key findings linking MAO-related enzymatic and gene activity and aggressive behavior, and, finally, we offer novel insights into the mechanisms underlying this association. Using the existing experimental evidence as a foundation, we discuss the translational implications of these findings in clinical practice and highlight what we believe are outstanding conceptual and methodological questions in the field. Ultimately, we propose that unraveling the specific role of MAO in aggression requires an integrated approach, where this question is pursued by combining psychological, radiological, and genetic/genomic assessments. The translational benefits of such an approach include the discovery of novel biomarkers of aggression and targeting the MAO system to modulate pathological aggression in clinical populations.

Intoxication Effects on Impulsive Alcohol Choice in Heavy Drinkers: Correlation With Sensation Seeking and Differential Effects by Commodity

BACKGROUND

The preference for immediate rewards and high sensation seeking are both potent risk factors for alcohol use disorder (AUD), but how they interact during intoxication is poorly understood. To model decision making linked to AUD risk, we tested heavy drinkers for impulsive choice (delay discounting with alcohol:money or money:money) and behavioral sensation seeking using a novel odor choice task. Laboratory tasks measured actual behavior with real contingencies. Our goals were to determine, in heavy drinkers, (i) alcohol's effects on delay discounting, and (ii) how AUD risk factors relate to delay discounting, and (iii) how delay discounting with alcohol choices compares with strictly monetary choices.

METHODS

Thirty-five heavy drinkers (≥2 binges per month; age = 22.8 ± 2.2; 20 male; 5.8 ± 2.3 drinks/drinking day) performed cross-commodity discounting (CCD) of immediate alcohol vs. delayed money, a monetary delay discounting (DD), and behavioral sensation-seeking tasks. CCD and DD were performed while sober and during controlled alcohol infusion targeting 0.08 g/dl. The behavioral sensation-seeking task presented binary choices of odorants varying in intensity and novelty, and the risk of exposure to a malodorant.

RESULTS

CCD and DD behaviors were highly correlated across conditions, mean r = 0.64. Alcohol increased delayed reward preference in DD, p = 0.001, but did not alter mean CCD, p > 0.16. However, alcohol-induced changes in CCD correlated with behavioral sensation seeking, such that higher sensation seekers' immediate alcohol preference increased when intoxicated, p = 0.042; self-reported sensation seeking was uncorrelated, ps > 0.08. Behavioral sensation seeking also correlated with "want" alcohol following a priming dose targeting 0.035 g/dl, p = 0.021. CCD and DD did not correlate with self-reported drinking problems or other personality risk traits.

CONCLUSIONS

Alcohol increased impulsive alcohol choice in high sensation seekers, suggesting an interaction that may underlie impaired control of drinking, at least in a subset of heavy drinkers-consistent with models highlighting high novelty/sensation-seeking AUD subtypes. Discounting behavior overall appears to be a generalized process, and relatively stable across methods, repeated testing, and intoxication. These findings further support the utility of behavioral tasks in uncovering key behavioral phenotypes in AUD.

The evolutionary genetics of personality

Genetic influences on personality differences are ubiquitous, but their nature is not well understood. A theoretical framework might help, and can be provided by evolutionary genetics. We assess three evolutionary genetic mechanisms that could explain genetic variance in personality differences: selective neutrality, mutation‐selection balance, and balancing selection. Based on evolutionary genetic theory and empirical results from behaviour genetics and personality psychology, we conclude that selective neutrality is largely irrelevant, that mutation‐selection balance seems best at explaining genetic variance in intelligence, and that balancing selection by environmental heterogeneity seems best at explaining genetic variance in personality traits. We propose a general model of heritable personality differences that conceptualises intelligence as fitness components and personality traits as individual reaction norms of genotypes across environments, with different fitness consequences in different environmental niches. We also discuss the place of mental health in the model. This evolutionary genetic framework highlights the role of gene‐environment interactions in the study of personality, yields new insight into the person‐situation‐debate and the structure of personality, and has practical implications for both quantitative and molecular genetic studies of personality. Copyright © 2007 John Wiley & Sons, Ltd.

Gene Flow by Selective Emigration as a Possible Cause for Personality Differences between Small Islands and Mainland Populations

Whether personality differences exist between populations is a controversial question. Even though such differences can be measured, it is still not clear whether they are due to individual phenotypic responses to the environment or whether they have a genetic influence. In a population survey we compared the personality traits of inhabitants of an Italian archipelago (the three Egadi islands; N = 622) with those of the closest mainland population (Trapani area; N = 106) and we found that personality differences between small populations can be detected. Islanders scored significantly lower on the personality traits of openness to experience and extraversion and higher on conscientiousness. We suggest that these personality trait differences could be an adaptive response to a confined socio–environmental niche, genetically produced by a strong, non–random gene flow in the last 20–25 generations, rather than the flexible response of islanders to environmental variables. To test this hypothesis, we compared subsets of the islander population classified by ancestry, birthplace, immigration and emigration and found that differences in extraversion can be accounted for by gene flow, while openness to experience and conscientiousness can also be accounted for by some gene–environment interactions. We propose a Personality Gene Flow hypothesis suggesting that, in small isolated communities, whenever there is strong, non–random emigration, paired with weak and random immigration, we can expect rapid genetic personality change within the population. Copyright © 2010 John Wiley & Sons, Ltd.

The Dopamine D4 Receptor (DRD4) Exon 3 VNTR Contributes to Adaptive Personality Differences in an Italian Small Island Population

The search for evolutionary forces shaping the diversity of human personality traits encouraged studies that have found that islanders are relatively closed and introverted, with little interest in the external world. The ‘personality gene flow’ hypothesis was proposed to explain the mechanism underlying this difference, suggesting that the frequency of alleles that influence islander personality traits might progressively increase in the gene pools on islands because of selective emigration of individuals not displaying these alleles. We genotyped 96 individuals from the Italian mainland and 117 from Giglio Island, whose residents were previously assessed regarding their personality traits. We genotyped three polymorphisms: the dopamine D4 receptor (DRD4) exon 3 repeat region, the serotonin–transporter SLC6A4 5–HTTLPR indel and the dopamine transporter SLC6A3 DAT1 3′UTR repeat region. Only the DRD4 exon 3 repeat was hypothesised to show varying allele frequencies because this polymorphism could be associated with human migration and personality traits such as extraversion, openness and novelty seeking. As predicted, no differences in allele frequencies were found for the SLC6A4 and SLC6A3 polymorphisms, whereas significant differences were observed in the frequency of the DRD4 exon 3 alleles. The DRD4.2 repeat was more common in mainlanders, as expected, whereas the DRD4.7 allele was over–represented among islanders who never emigrated. This last result contradicts the suggested association of this allele with long–distance migrations. We suggest that emigration might have caused gene flow out the island that resulted in somewhat unpredictable changes in the frequencies of specific alleles, thus influencing islander personality traits. Copyright © 2013 European Association of Personality Psychology

Evolution, genes, and inter‐disciplinary personality research

Most commentaries welcomed an evolutionary genetic approach to personality, but several raised concerns about our integrative model. In response, we clarify the scientific status of evolutionary genetic theory and explain the plausibility and value of our evolutionary genetic model of personality, despite some shortcomings with the currently available theories and data. We also have a closer look at mate choice for personality traits, point to promising ways to assess evolutionarily relevant environmental factors and defend higher‐order personality domains and the g‐factor as the best units for evolutionary genetic analyses. Finally, we discuss which extensions of and alternatives to our model appear most fruitful, and end with a call for more inter‐disciplinary personality research grounded in evolutionary theory. Copyright © 2007 John Wiley & Sons, Ltd.

DRD4 genotyping may differentiate symptoms of attention-deficit/hyperactivity disorder and sluggish cognitive tempo

OBJECTIVE

Studies to reduce the heterogeneity of attention-deficit/hyperactivity disorder (ADHD) have increased interest in the concept of sluggish cognitive tempo (SCT). The aim of this study was to investigate if the prevalence of two variable-number tandem repeats (VNTRs) located within the 3'-untranslated region of the DAT1 gene and in exon 3 of the dopamine D4 receptor (DRD4) gene differ among four groups (31 subjects with SCT but no ADHD, 146 individuals with ADHD but no SCT, 67 subjects with SCT + ADHD, and 92 healthy controls).

METHODS

We compared the sociodemographic profiles, neurocognitive domains, and prevalence of two VNTRs in SCT and ADHD subjects versus typically developing (TD) controls.

RESULTS

The SCT without ADHD group had a higher proportion of females and lower parental educational attainment. Subjects in this group performed worse on neuropsychological tests, except for psychomotor speed and commission errors, compared to controls. However, the ADHD without SCT group performed significantly worse on all neuropsychological domains than controls. We found that 4R homozygosity for the DRD4 gene was most prevalent in the ADHD without SCT group. The SCT without ADHD group had the highest 7R allele frequency, differing significantly from the ADHD without SCT group.

CONCLUSION

The 7R allele of DRD4 gene was found to be significantly more prevalent in SCT cases than in ADHD cases. No substantial neuropsychological differences were found between SCT and ADHD subjects.

Right Posterior Insula and Putamen Volume Mediate the Effect of Oxytocin Receptor Polygenic Risk for Autism Spectrum Disorders on Reward Dependence in Healthy Adults

Much evidence indicates the influence of the oxytocin receptor (OXTR) gene on autism spectrum disorders (ASDs), a set of disorders characterized by a range of deficits in prosocial behaviors, which are closely related to the personality trait of reward dependence (RD). However, we do not know the effect of the OXTR polygenic risk score for ASDs (OXTR-PRSASDs) on RD and its underlying neuroanatomical substrate. Here, we aimed to investigate associations among the OXTR-PRSASDs, gray matter volume (GMV), and RD in two independent datasets of healthy young adults (n = 450 and 540). We found that the individuals with higher OXTR-PRSASDs had lower RD and significantly smaller GMV in the right posterior insula and putamen. The GMV of this region showed a positive correlation with RD and a mediation effect on the association between OXTR-PRSASDs and RD. Moreover, the correlation map between OXTR-PRSASDs and GMV showed spatial correlation with OXTR gene expression. All results were highly consistent between the two datasets. These findings highlight a possible neural pathway by which the common variants in the OXTR gene associated with ASDs may jointly impact the GMV of the right posterior insula and putamen and further affect the personality trait of RD.

Effect of COMT Val158Met polymorphism on personality traits and educational attainment in a longitudinal population representative study

The COMT Val158Met polymorphism has been associated with anxiety and affective disorders, but its effect on anxiety-related personality traits varies between studies. Our purpose was to investigate the effect of COMT Val158Met on personality traits from adolescence to young adulthood in a population representative Caucasian birth cohort. Also its association with educational attainment and anxiety and mood disorders by the age 25 were examined. This analysis is based on the older cohort of the Estonian Children Personality Behavior and Health Study (original number of subjects 593). The personality traits were assessed when the participants were 15, 18 and 25 years old. COMT Val158Met had an effect on Neuroticism in females by age 25 (p = 0.001, Bonferroni-corrected for five traits), whereas female Val homozygotes scored the highest. In addition, the Conscientiousness scores of subjects with Val/Val genotype were decreasing in time, being the lowest by the age 25 (p = 0.006, Bonferroni-corrected for five traits). By the age 25, males with the Val/Met genotype had mainly secondary or vocational education, whereas female heterozygotes mostly had obtained or were obtaining university education. COMT Val158Met was not associated with anxiety or mood disorders in either gender. These results suggest that genes affecting dopamine system are involved in the development of personality traits and contribute to educational attainment.

Demographic consequences and characteristics of recent population mixing and colonization in Steller sea lions, Eumetopias jubatus

Steller sea lions (Eumetopias jubatus) are composed of two genetically distinct metapopulations (an increasing “eastern” and a reduced and endangered “western” population, or stock for management purposes in U.S. waters) that are only recently mixing at new rookeries in northern Southeast Alaska, east of the current stock boundary. We used mark-recapture models and 18 years of resighting data of over 3,500 individuals marked at the new rookeries and at neighboring long-established rookeries in both populations to examine morphology, survival, and movement patterns of pups born at new rookeries based on whether they had mitochondrial DNA haplotypes from the western or eastern population (mtW or mtE); examine survival effects of dispersal to the Eastern Stock region for animals born in the Western Stock region; and estimate minimum proportions of animals with western genetic material in regions within Southeast Alaska. Pups born at new rookeries with mtW had similar mass, but reduced body condition and first-year survival (approximately −10%) compared to pups with mtE. mtE pups ranged more widely than mtW pups, including more to the sheltered waters of Southeast Alaska’s Inside Passage. Fitness benefits for western-born females that dispersed to Southeast Alaska were observed as higher female survival (+0.127, +0.099, and +0.032 at ages 1, 2, and 3+) and higher survival of their female offspring to breeding age (+0.15) compared to females that remained west of the boundary. We estimated that a minimum of 38% and 13% of animals in the North Outer Coast–Glacier Bay and Lynn Canal–Frederick Sound regions in Southeast Alaska, respectively, carry genetic information unique to the western population. Despite fitness benefits to western females that dispersed east, asymmetric dispersal costs or other genetic or maternal effects may limit the growth of the western genetic lineage at the new rookeries, and these factors require further study.

Classification of Participants Based on Increase-Decrease Rate Model of Reaction Time to Personality Trait Words

In this experiment, we tried to measure personality by reaction time (RT) to stimuli of personality trait words. There were interindividual and intraindividual differences in the factors that caused the reaction time to fluctuate. The intraindividual differences for personality trait words were caused by changes due to circumstances for the same participant. The increased stimulus reaction time (sRT) model for simple reaction time was used as an index to indicate personality traits. As a result, participants could be classified into two major hierarchical clusters. The participants in Cluster 1 showed innovative dominance. The participants in Cluster 2 were obedient and conservative. The independent variable was measured by the physiological index using sRT for classify the participants. Participants in Cluster 2 had a reduced stress response to the experiment and showed a tendency to be compliant. Moreover, immediately after the RT measurement session with a laptop computer started, participants in Cluster 1 showed decreased HEG and increased amylase values and had a somewhat negative attitude. The physiological dependent variable were measured by using salivary amylase and hemoencephalography (HEG). And, the psychological dependent variable was the Big Five personality inventory. All of them ware using to verify the participant’s classification. Participants in Cluster 2 had significantly higher conscientiousness than those in Cluster 1. Therefore, we suggest that it is possible to classify personality traits from RT by using sRT based on intraindividual differences.

Quantifying Behavioral Sensation Seeking With the Aroma Choice Task

Our goal was to develop a behavioral measure of sensation seeking (SS). The Aroma Choice Task (ACT) assesses preference for an intense, novel, varied, and risky (exciting) option versus a mild, safe (boring) option using real-time odorant delivery. A total of 147 healthy young adults completed 40 binary choice trials. We examined (1) intensity and pleasantness of odorants, (2) stability of responding, (3) association with SS self-report, and (4) association with self-reported illicit drug use. Participants' preference for the "exciting" option versus the safe option was significantly associated with self-reported SS (p < .001) and illicit drug use (p = .041). Odorant ratings comported with their intended intensity. The ACT showed good internal, convergent, and criterion validity. We propose that the ACT might permit more objective SS assessment for investigating the biological bases of psychiatric conditions marked by high SS, particularly addiction. The ACT measures SS behaviorally, mitigating some self-report challenges and enabling real-time assessment, for example, for functional magnetic resonance imaging (fMRI).

DRD4 exon 3 genotype and ADHD: Randomised pharmacodynamic investigation of treatment response to methylphenidate

Objectives: Dopamine plays an important role in modulating attention and motor behaviours, dimensions altered in attention deficit/hyperactivity disorder (ADHD). Numerous association studies have linked dopamine receptor 4 (DRD4) to increased risk of ADHD. This study investigated the effect of DRD4 exon 3 polymorphism on child behaviours in response to treatment with methylphenidate. Methods: A total of 374 children diagnosed with ADHD (ages 6-12 years) were evaluated under three experimental conditions: baseline, placebo and MPH (0.5 mg/kg/day). This was a 2-week prospective within-subject, placebo-controlled, crossover trial. The Conners' Global Index for parents and for teachers was used to evaluate the behaviours of the children. One-way repeated measures analysis of variance was used to test the effect of the interaction between DRD4 genotype and experimental conditions. Results: A significant interaction between DRD4 genotype and treatment was detected when the child's behaviour was evaluated by the parents (P = 0.035, effect size of 0.014), driven by a better treatment response in children homozygous for long 7-repeat allele. Conclusions: According to the parent assessment, children homozygous for the long 7-repeat allele were more responsive to experimental condition. This is the largest pharmacogenetic investigation of the effect of DRD4 exon 3 polymorphism in childhood ADHD. Trial Registration: clinicaltrials.gov, identifier NCT00483106.

Owner personality and the wellbeing of their cats share parallels with the parent-child relationship

Human personality may substantially affect the nature of care provided to dependants. This link has been well researched in parents and children, however, relatively little is known about this dynamic with regards to humans’ relationships with non-human animals. Owner interactions with companion animals may provide valuable insight into the wider phenomenon of familial interactions, as owners usually adopt the role of primary caregiver and potentially surrogate parent. This study, using cats as an exemplar, explored the relationship between owner personality and the lifestyles to which cats are exposed. In addition, it explored owner personality as it related to reported cat behaviour and wellbeing. Cat owners (n = 3331) responded to an online survey examining their personality and the health, behaviour and management of their cats. Owner personality was measured using the Big Five Inventory (BFI) to assess: Agreeableness, Conscientiousness, Extroversion, Neuroticism and Openness. Owners also provided information concerning the physical health, breed type, management and behavioural styles of their cats. Generalised linear mixed models were used to identify relationships between owner personality and a range of factors that may have welfare implications for the wider companion animal population, and specifically, cats. Higher owner Neuroticism was associated with an increased likelihood of non-pedigree rather than pedigree cat ownership, a decreased likelihood of ad libitum access to the outdoors, cats being reported as having a ‘behavioural problem’, displaying more aggressive and anxious/fearful behavioural styles and more stress-related sickness behaviours, as well as having an ongoing medical condition and being overweight. Other owner personality traits were generally found to correlate more positively with various lifestyle, behaviour and welfare parameters. For example, higher owner Extroversion was associated with an increased likelihood that the cat would be provided ad libitum access to the outdoors; higher owner Agreeableness was associated with a higher level of owner reported satisfaction with their cat, and with a greater likelihood of owners reporting their cats as being of a normal weight. Finally higher owner Conscientiousness was associated with the cat displaying less anxious/fearful, aggressive, aloof/avoidant, but more gregarious behavioural styles. These findings demonstrate that the relationship between carer personality and the care received by a dependent, may extend beyond the human family to animal-owner relationships, with significant implications for the choice of management, behaviour and potentially the broader wellbeing of companion animals.

Biological clock function is linked to proactive and reactive personality types

Background

Many physiological processes in our body are controlled by the biological clock and show circadian rhythmicity. It is generally accepted that a robust rhythm is a prerequisite for optimal functioning and that a lack of rhythmicity can contribute to the pathogenesis of various diseases. Here, we tested in a heterogeneous laboratory zebrafish population whether and how variation in the rhythmicity of the biological clock is associated with the coping styles of individual animals, as assessed in a behavioural assay to reliably measure this along a continuum between proactive and reactive extremes.

Results

Using RNA sequencing on brain samples, we demonstrated a prominent difference in the expression level of genes involved in the biological clock between proactive and reactive individuals. Subsequently, we tested whether this correlation between gene expression and coping style was due to a consistent change in the level of clock gene expression or to a phase shift or to altered amplitude of the circadian rhythm of gene expression. Our data show a remarkable individual variation in amplitude of the clock gene expression rhythms, which was also reflected in the fluctuating concentrations of melatonin and cortisol, and locomotor activity. This variation in rhythmicity showed a strong correlation with the coping style of the individual, ranging from robust rhythms with large amplitudes in proactive fish to a complete absence of rhythmicity in reactive fish. The rhythmicity of the proactive fish decreased when challenged with constant light conditions whereas the rhythmicity of reactive individuals was not altered.

Conclusion

These results shed new light on the role of the biological clock by demonstrating that large variation in circadian rhythmicity of individuals may occur within populations. The observed correlation between coping style and circadian rhythmicity suggests that the level of rhythmicity forms an integral part of proactive or reactive coping styles.

Electronic supplementary material

The online version of this article (10.1186/s12915-018-0618-0) contains supplementary material, which is available to authorized users.

Temperament and character profiles for children with ADHD with and without tic disorders

There is no research about whether ADHD with tic disorder that temperamental features that differ from the ADHD. This research aimed to identify temperament and character profiles for children with ADHD according to tic disorder by comparing them with a healthy control group. A discriminant analysis was conducted to identify whether temperament and character profiles can discriminate comorbidity. The sample consisted of three groups (N = 40 per group): ADHD alone, ADHD with tic disorder and age- and sex- matched healthy control. The parents of 120 children (mean age 8.57 ± 1.71 years) completed the Junior Temperament and Character Inventory (JTCI). The two ADHD groups showed higher novelty seeking and low persistence, self-directedness and cooperativeness than the control group. The ADHD alone group had lower scores for persistence and self-directedness than the other two groups. Temperament and character profiles were useful for discriminating ADHD from the control group. However, their discriminating power was relatively low for all three groups. Results indicated that differences in temperament and character in ADHD children were present according to comorbid tic disorders. JTCI's discriminating power for ADHD alone and ADHD with tic disorder was relatively lower than that of the combined ADHD group and the control group.

The Development of Latent Dimensions of Psychopathology across Early Childhood: Stability of Dimensions and Moderators of Change

Recent research has described the structure of psychopathology as including one general and multiple specific factors, and this structure has been found in samples across development. However, little work has examined whether this structure is consistent across time, particularly in young children, within the same sample. Further, few studies have examined factors that influence the magnitude of the stability of latent dimensions of psychopathology. In the present study, we examine these issues in a community sample of 545 children assessed at ages 3 and 6. In addition, we explored child temperament, parental history of psychopathology, and parenting behaviors as potential moderators of the longitudinal stability of latent dimensions of psychopathology. We found that the same bifactor model structure identified at age 3 provided an adequate fit to the data at age 6. Further, our model revealed significant homotypic stability of the general, internalizing, and externalizing specific factors. We also found evidence of differentiation of psychopathology over time with the general factor at age 3 predicting the externalizing factor at age 6. However, we failed to identify moderators of the longitudinal associations between psychopathology latent factors. Overall, our results bolster support for the bifactor structure of psychopathology, particularly in early childhood.

Temperament and Character Inventory in Bipolar Disorder versus Healthy Controls and Modulatory Effects of 3 Key Functional Gene Variants

BACKGROUND

Bipolar disorder (BD) has been associated with temperamental and personality traits, although the relationship is still to be fully elucidated. Several studies investigated the genetic basis of temperament and character, identifying catechol-O-methyltransferase (COMT), brain derived neurotrophic factor (BDNF), and serotonin transporter (5-HTT) gene variants as strong candidates.

METHODS

In the GECO-BIP study, 125 BD patients and 173 HC were recruited. Subjects underwent to a detailed assessment and the temperament and character inventory 125 items (TCI) was administrated. Three functional genetic variants within key candidate genes (COMT rs4680, BDNF rs6265, and the serotonin-transporter-linked polymorphic region (5-HTTLPR)) were genotyped. Univariate and multivariate analyses were performed.

RESULTS

Compared to HC, BD patients showed higher scores in novelty seeking (NS; p = 0.001), harm avoidance (HA; p < 0.001), and self transcendence (St; p < 0.001), and lower scores in self directness (p < 0.001) and cooperativeness (p < 0.001) TCI dimensions. Concerning the genetic analyses, COMT rs4680 was associated with NS in the total sample (p = 0.007) and in the male subsample (p = 0.022). When performing the analysis in the HC and BD samples, the association was confirmed only in HC (p = 0.012), and in the HC male subgroup in particular (p = 0.004). BDNF rs6265 was associated with St in the BD group (p = 0.017).

CONCLUSION

COMT rs4680 may modulate NS in males in the general population. This effect was not detected in BD patients, probably because BD alters the neurobiological basis of some TCI dimensions. BDNF rs6265 seems to modulate St TCI dimension only in BD patients, possibly modulating the previously reported association between rs6265 and BD treatment response. Further studies are needed to confirm our findings.

Opinion on monoaminergic contributions to traits and temperament

This article critically reviews evidence relating temperamental traits and personality factors to the monoamine neurotransmitters, especially dopamine and serotonin. The genetic evidence is not yet considered to be conclusive and it is argued that basic neuroscience research on the neural basis of behaviour in experimental animals should be taken more into account. While questionnaire and lexical methodology including the 'Five Factor' theory has been informative (mostly for the traits relevant to social functioning, i.e. personality), biologically oriented approaches should be employed with more objective, theoretically grounded measures of cognition and behaviour, combined with neuroimaging and psychopharmacology, where appropriate. This strategy will enable specific functions of monoamines and other neuromodulators such as acetylcholine and neuropeptides (such as orexin) to be defined with respect to their roles in modulating activity in specific neural networks-leading to a more realistic definition of their interactive roles in complex, biologically based traits (i.e. temperament).This article is part of the theme issue 'Diverse perspectives on diversity: multi-disciplinary approaches to taxonomies of individual differences'.

The genetics of human personality

Personality traits are the relatively enduring patterns of thoughts, feelings and behaviors that reflect the tendency to respond in certain ways under certain circumstances. Twin and family studies have showed that personality traits are moderately heritable, and can predict various lifetime outcomes, including psychopathology. The Research Domain Criteria characterizes psychiatric diseases as extremes of normal tendencies, including specific personality traits. This implies that heritable variation in personality traits, such as neuroticism, would share a common genetic basis with psychiatric diseases, such as major depressive disorder. Despite considerable efforts over the past several decades, the genetic variants that influence personality are only beginning to be identified. We review these recent and increasingly rapid developments, which focus on the assessment of personality via several commonly used personality questionnaires in healthy human subjects. Study designs covered include twin, linkage, candidate gene association studies, genome-wide association studies and polygenic analyses. Findings from genetic studies of personality have furthered our understanding about the genetic etiology of personality, which, like neuropsychiatric diseases themselves, is highly polygenic. Polygenic analyses have showed genetic correlations between personality and psychopathology, confirming that genetic studies of personality can help to elucidate the etiology of several neuropsychiatric diseases.

Monoamine Oxidase A (MAOA) Gene and Personality Traits from Late Adolescence through Early Adulthood: A Latent Variable Investigation

Very few molecular genetic studies of personality traits have used longitudinal phenotypic data, therefore molecular basis for developmental change and stability of personality remains to be explored. We examined the role of the monoamine oxidase A gene (MAOA) on extraversion and neuroticism from adolescence to adulthood, using modern latent variable methods. A sample of 1,160 male and 1,180 female participants with complete genotyping data was drawn from a British national birth cohort, the MRC National Survey of Health and Development (NSHD). The predictor variable was based on a latent variable representing genetic variations of the MAOA gene measured by three SNPs (rs3788862, rs5906957, and rs979606). Latent phenotype variables were constructed using psychometric methods to represent cross-sectional and longitudinal phenotypes of extraversion and neuroticism measured at ages 16 and 26. In males, the MAOA genetic latent variable (AAG) was associated with lower extraversion score at age 16 (β = −0.167; CI: −0.289, −0.045; p = 0.007, FDRp = 0.042), as well as greater increase in extraversion score from 16 to 26 years (β = 0.197; CI: 0.067, 0.328; p = 0.003, FDRp = 0.036). No genetic association was found for neuroticism after adjustment for multiple testing. Although, we did not find statistically significant associations after multiple testing correction in females, this result needs to be interpreted with caution due to issues related to x-inactivation in females. The latent variable method is an effective way of modeling phenotype- and genetic-based variances and may therefore improve the methodology of molecular genetic studies of complex psychological traits.

[A role of interactions between N-methyl-D-aspartate and dopamine receptors in facial emotion recognition impairment in schizophrenia]

AIM

To search for genetic mechanisms of facial emotion recognition (FER) impairment, one of the features of schizophrenia that affects social adaptation of patients. Based on the view implicating the interplay between dopaminergic and glutamatergic systems into the pathogenesis of schizophrenia, authors explored the interaction effects of the C366G polymorphism in the GRIN2B gene encoding NMDA receptor subunit NR2B with ANKK1/DRD2 Taq1A and 48-VNTR DRD4 polymorphisms on FER.

MATERIAL AND METHODS

GRIN2B -DRD2 interaction effects were studied in a sample of 237 patients and 235 healthy controls, GRIN2B - DRD4 in 268 patients and 208 controls.

RESULTS AND CONCLUSION

Both effects were significant in combined samples of patients and controls (GRIN2B X DRD2, F=4.12, p=0.043; GRIN2B X DRD4, F=6.43, p=0.012). Further analysis confirmed the interaction effect of GRIN2B and DRD2 polymorphisms on FER in patients with schizophrenia. In patients with a less efficient allele of the DRD2 in the absence of the minor allele of the GRIN2B C366G polymorphism, the results were close to normal values while patients with minor alleles of both polymorphisms showed the worst results. This finding is in line with the conceptions on a possible role of NMDA-receptor hypofunction and D2-mediated regulation of NMDA-receptor activity in FER impairments in schizophrenia.

Using a Systems-Based Risk Score Approach to Examine Genetic Predisposition to Novelty Seeking

Abstract. Previous research is mixed regarding the relation between dopamine and Novelty Seeking. The goals of the current study were to support the hypotheses that Novelty Seeking is associated with dopamine genes and that modeling genetic risk score increases the utility of genetic information in hypothesis-driven research. The results showed that higher hypodopaminergic genetic risk score positively predicted higher Novelty Seeking score, F(1, 115) = 5.76, p < .01, R2 = 0.06. The findings support study hypotheses and, in combination with previous studies, show the utility of empirically validated system-based risk scores as a means of modeling genetic predisposition in neurobiological systems. This approach provides a mechanism for incorporating genetic predisposition into theory-driven multivariate etiological models of psychological constructs such as personality and mental illness.

Externalizing Problem Behavior in Adolescence: Parenting Interacting With DAT1 and DRD4 Genes

This study extends previous gene-by-environment (G × E) research through design and methodological advances and examines alternative hypotheses of diathesis stress, vantage sensitivity, and differential susceptibility. In a sample of 984 adolescents and their parents, we examined whether effects of parental support, proactive, punitive, harsh punitive, and psychological control on externalizing problem behavior are moderated by adolescents' genotype for the dopamine transporter (DAT1) or receptor D4 (DRD4) gene. Results provided evidence for main effects of parenting behavior and DRD4, and multiple interaction effects of which one survived Bonferroni correction. Adolescents carrying a long DRD4 variant were more susceptible to the effects of parental proactive control on aggression, for better and for worse. Critical considerations were made regarding the complexity of G × E research.

Interhemispheric gene expression differences in the cerebral cortex of humans and macaque monkeys

Handedness and language are two well-studied examples of asymmetrical brain function in humans. Approximately 90% of humans exhibit a right-hand preference, and the vast majority shows left-hemisphere dominance for language function. Although genetic models of human handedness and language have been proposed, the actual gene expression differences between cerebral hemispheres in humans remain to be fully defined. In the present study, gene expression profiles were examined in both hemispheres of three cortical regions involved in handedness and language in humans and their homologues in rhesus macaques: ventrolateral prefrontal cortex, posterior superior temporal cortex (STC), and primary motor cortex. Although the overall pattern of gene expression was very similar between hemispheres in both humans and macaques, weighted gene correlation network analysis revealed gene co-expression modules associated with hemisphere, which are different among the three cortical regions examined. Notably, a receptor-enriched gene module in STC was particularly associated with hemisphere and showed different expression levels between hemispheres only in humans.

Maternal and paternal personality profiles of adolescent suicide attempters

Personality features have been correlated with suicidal behaviors in recent decades. Given its neurobiological background, Cloninger's model of personality, the Temperament and Character Inventory (TCI), may help to identify the maternal and paternal personality dimensions associated with adolescent suicide attempts. The present study is the first that specifically compares the temperament and character profiles of both mothers and fathers of the adolescent suicide attempters with a control group, by considering the influence of demographic and clinical factors. The study group comprised 117 parents of 71 adolescent suicide attempters and 119 parents of 71 age- and gender-matched adolescents without a suicide attempt included as a control group. The TCI and Brief Symptom Inventory (BSI) were applied to the parents in both groups. Logistic regression analysis, which was performed to adjust confounding factors, demonstrated significantly higher scores for harm avoidance among the mothers and lower scores of self-directedness among the fathers of the adolescent suicide attempters. New psychotherapeutic modalities considering the high-risk parental personality traits would be beneficial to support parent-adolescent relationships and may have a preventative effect on adolescent suicide.

Association between Age and the 7 Repeat Allele of the Dopamine D4 Receptor Gene

Longevity is in part (25%) inherited, and genetic studies aim to uncover allelic variants that play an important role in prolonging life span. Results to date confirm only a few gene variants associated with longevity, while others show inconsistent results. However, GWAS studies concentrate on single nucleotide polymorphisms, and there are only a handful of studies investigating variable number of tandem repeat variations related to longevity. Recently, Grady and colleagues (2013) reported a remarkable (66%) accumulation of those carrying the 7 repeat allele of the dopamine D4 receptor gene in a large population of 90-109 years old Californian centenarians, as compared to an ancestry-matched young population. In the present study we demonstrate the same association using continuous age groups in an 18-97 years old Caucasian sample (N = 1801, p = 0.007). We found a continuous pattern of increase from 18-75, however frequency of allele 7 carriers decreased in our oldest age groups. Possible role of gene-environment interaction effects driven by historical events are discussed. In accordance with previous findings, we observed association preferentially in females (p = 0.003). Our results underlie the importance of investigating non-disease related genetic variants as inherited components of longevity, and confirm, that the 7-repeat allele of the dopamine D4 receptor gene is a longevity enabling genetic factor, accumulating in the elderly female population.

Further evidence of the limited role of candidate genes in relation to infant-mother attachment outcomes

In this paper, we examine the associations between specific candidate genes (DRD2, DRD4, COMT, biallelic and tri-allelic 5HTTLPR, and OXTR) and infant attachment outcomes as main effects and in conjunction with maternal sensitivity. The sample included 200 infants (97 European American, 94 African-American, and 9 biracial) and their mothers. Maternal sensitivity and overtly negative maternal behavior were observed when infants were 6 months and 1 year old in distress-eliciting contexts, attachment was assessed via the Strange Situation at age 1, and DNA samples were collected when children were 2 years old. Consistent with recent research in large samples, there was little evidence that these genes are associated with attachment security, disorganization, or distress as main effects (in additive, dominant, and homozygous models) or in conjunction with maternal sensitivity or overtly negative behavior (primarily dominance models). Furthermore, there was little evidence that associations vary as a function of race.

SNP-based heritability estimates of the personality dimensions and polygenic prediction of both neuroticism and major depression: findings from CONVERGE

Biometrical genetic studies suggest that the personality dimensions, including neuroticism, are moderately heritable (~0.4 to 0.6). Quantitative analyses that aggregate the effects of many common variants have recently further informed genetic research on European samples. However, there has been limited research to date on non-European populations. This study examined the personality dimensions in a large sample of Han Chinese descent (N=10 064) from the China, Oxford, and VCU Experimental Research on Genetic Epidemiology study, aimed at identifying genetic risk factors for recurrent major depression among a rigorously ascertained cohort. Heritability of neuroticism as measured by the Eysenck Personality Questionnaire (EPQ) was estimated to be low but statistically significant at 10% (s.e.=0.03, P=0.0001). In addition to EPQ, neuroticism based on a three-factor model, data for the Big Five (BF) personality dimensions (neuroticism, openness, conscientiousness, extraversion and agreeableness) measured by the Big Five Inventory were available for controls (n=5596). Heritability estimates of the BF were not statistically significant despite high power (>0.85) to detect heritabilities of 0.10. Polygenic risk scores constructed by best linear unbiased prediction weights applied to split-half samples failed to significantly predict any of the personality traits, but polygenic risk for neuroticism, calculated with LDpred and based on predictive variants previously identified from European populations (N=171 911), significantly predicted major depressive disorder case-control status (P=0.0004) after false discovery rate correction. The scores also significantly predicted EPQ neuroticism (P=6.3 × 10-6). Factor analytic results of the measures indicated that any differences in heritabilities across samples may be due to genetic variation or variation in haplotype structure between samples, rather than measurement non-invariance. Findings demonstrate that neuroticism can be significantly predicted across ancestry, and highlight the importance of studying polygenic contributions to personality in non-European populations.

Novelty Seeking and Drug Addiction in Humans and Animals: From Behavior to Molecules

Global treatment of drug addiction costs society billions of dollars annually, but current psychopharmacological therapies have not been successful at desired rates. The increasing number of individuals suffering from substance abuse has turned attention to what makes some people more vulnerable to drug addiction than others. One personality trait that stands out as a contributing factor is novelty seeking. Novelty seeking, affected by both genetic and environmental factors, is defined as the tendency to desire novel stimuli and environments. It can be measured in humans through questionnaires and in rodents using behavioral tasks. On the behavioral level, both human and rodent studies demonstrate that high novelty seeking can predict the initiation of drug use and a transition to compulsive drug use and create a propensity to relapse. These predictions are valid for several drugs of abuse, such as alcohol, nicotine, cocaine, amphetamine, and opiates. On the molecular level, both novelty seeking and addiction are modulated by the central reward system in the brain. Dopamine is the primary neurotransmitter involved in the overlapping neural substrates of both parameters. In sum, the novelty-seeking trait can be valuable for predicting individual vulnerability to drug addiction and for generating successful treatment for patients with substance abuse disorders.

Positive Association Between Limbic Metabotropic Glutamate Receptor 5 Availability and Novelty-Seeking Temperament in Humans: An 18F-FPEB PET Study

Heritable temperament traits have been linked to several neuropsychiatric illnesses, including disorders associated with metabotropic glutamate receptor 5 (mGluR5) and dopaminergic dysfunctions. Considering its modulating effect on neurotransmission, we hypothesized that cerebral mGluR5 availability is associated with temperament traits in healthy humans.

METHODS

Forty-four nonsmoking healthy volunteers (mean age ± SD, 40 ± 14 y; age range, 22-66 y; 22 women) were included in this cross-sectional investigation. Brain mGluR5 availability was quantified on both a voxel-by-voxel and a volume-of-interest basis using the total distribution volume of the radioligand ¹⁸F-3-fluoro-5-[(pyridin-3-yl)ethynyl]benzonitrile (¹⁸F-FPEB) with 90-min dynamic PET and arterial input function. Moreover, glutamate-glutamine concentrations in the anterior cingulate cortex were measured using MR spectroscopy. These measures were related to the temperament traits of the 240-item Cloninger temperament and character inventory using a regression analysis with age and sex as nuisance variables.

RESULTS

High novelty-seeking temperament was robustly associated with increased mGluR5 availability in various regions including the thalamus (r = 0.71; the strongest association), amygdala, parahippocampus, insula, anterior and posterior cingulate cortex, and several primary sensory areas (all r > 0.58; P < 0.05, corrected for familywise error). These associations were specific because no correlations were found with other temperament scales or with spectroscopic measures of glutamatergic transmission.

CONCLUSION

Overall, these data posit mGluR5 in key paralimbic areas as a strong determinant of the temperament trait novelty seeking. These data add to our understanding of how brain neurochemistry accounts for the variation in human behavior and strongly support further research on mGluR5 as a potential therapeutic target in neuropsychiatric disorders associated with abnormal novelty-seeking behaviors.

Association between neurological soft signs, temperament and character in patients with schizophrenia and non-psychotic relatives

The heritability of schizophrenia and most personality traits has been well established, but the role of personality in susceptibility to schizophrenia remains uncertain. The aim of this study was to test for an association between personality traits and Neurological Soft Signs (NSS), a well-known biological marker of schizophrenia, in non-psychotic relatives of patients with schizophrenia. For this purpose, we evaluated the NSS scale and personality measured by the Temperament and Character inventory (TCI-R) in three groups of subjects: 29 patients with schizophrenia, 24 unaffected relatives and 37 controls. The results showed that patients with schizophrenia were more asocial (higher harm avoidance and lower reward dependence), more perseverative (higher persistence), and more schizotypal (lower self-directedness and cooperativeness, higher self-transcendence). The unaffected relatives showed higher harm avoidance, lower self-directedness and cooperativeness than the healthy controls. Higher NSS scores and sub-scores were found in patients and non-psychotic relatives compared with the controls. Among all the patients, total NSS scores were positively correlated with harm avoidance but negatively correlated with novelty seeking and persistence. Total NSS were also correlated with low scores on self-directedness and cooperativeness, which are indicators of personality disorder. Our results show that susceptibility to NSS and to schizophrenia are both related to individual differences in the temperament and character features in non-psychotic relatives of patients with schizophrenia. High harm avoidance, low persistence, low self-directedness and low cooperativeness contribute to both the risk of NSS and schizophrenia. These findings highlight the value of using both assessments to study high risk populations.

The analysis of anxiety and mood in healthy late-reproductive-stage women with regard to hormonal and genetic factors

The purpose of this study was to determine whether anxiety and mood disorders in late-reproductive-stage women are related to the serotonin transporter and monoamine oxidase A gene polymorphisms. Research instrument used in this study were the State-Trait Anxiety Inventory and the UWIST Mood Adjective Checklist. The 44-bp VNTR polymorphism in the 5-HTT (SLC 6A4) promoter region and the 30-bp VNTR polymorphism in the MAO-A promoter region were analyzed. The study included 345 healthy Polish women in the late reproductive stage. The mean age of the participants was 42.3 ± 4.5 years. State anxiety was observed in 16.8 % of the women and trait anxiety in 14.5 %. There were no statistically significant differences in the mood and the mean levels of anxiety depending on the presence of the polymorphisms analyzed in this study. Depressed mood is frequent among healthy women in the late reproductive stage. Anxiety is definitely less common. The study did not demonstrate the relationship between the 5-HTT and MAO-A gene polymorphisms, and the severity of anxiety and mood disorders in healthy late-reproductive-stage women.

Genetic mechanisms of parenting

This article is part of a Special Issue "Parental Care". The complexities of parenting behavior in humans have been studied for decades. Only recently did we begin to probe the genetic and epigenetic mechanisms underlying these complexities. Much of the research in this field continues to be informed by animal studies, where genetic manipulations and invasive tools allow to peek into and directly observe the brain during the expression of maternal behavior. In humans, studies of adult twins who are parents can suggest dimensions of parenting that might be more amenable to a genetic influence. Candidate gene studies can test specific genes in association with parental behavior based on prior knowledge of those genes' function. Gene-by-environment interactions of a specific kind indicating differential susceptibility to the environment might explain why some parents are more resilient and others are more vulnerable to stressful life events. Epigenetic studies can provide the bridge often necessary to explain why some individuals behave differently from others despite common genetic influences. There is a much-needed expansion in parenting research to include not only mothers as the focus-as has been the case almost exclusively to date-but also fathers, grandparents, and other caregivers.

Association between the dopamine D4 receptor gene exon III variable number of tandem repeats and political attitudes in female Han Chinese

Twin and family studies suggest that political attitudes are partially determined by an individual's genotype. The dopamine D4 receptor gene (DRD4) exon III repeat region that has been extensively studied in connection with human behaviour, is a plausible candidate to contribute to individual differences in political attitudes. A first United States study provisionally identified this gene with political attitude along a liberal-conservative axis albeit contingent upon number of friends. In a large sample of 1771 Han Chinese university students in Singapore, we observed a significant main effect of association between the DRD4 exon III variable number of tandem repeats and political attitude. Subjects with two copies of the 4-repeat allele (4R/4R) were significantly more conservative. Our results provided evidence for a role of the DRD4 gene variants in contributing to individual differences in political attitude particularly in females and more generally suggested that associations between individual genes, and neurochemical pathways, contributing to traits relevant to the social sciences can be provisionally identified.

A Genetic Variant (COMT) Coding Dopaminergic Activity Predicts Personality Traits in Healthy Elderly

Association studies between the NEO five factor personality inventory and COMT rs4680 have focused on young adults and the results have been inconsistent. However, personality and cortical changes with age may put older adults in a more sensitive range for detecting a relationship. The present study examined associations of COMT rs4680 and personality in older adults. Genetic association analyses were carried out between the NEO and the targeted COMT rs4680 in a large, well-characterized sample of healthy, cognitively normal older adults (N = 616, mean age = 69.26 years). Three significant associations were found: participants with GG genotype showed lower mean scores on Neuroticism (p = 0.039) and higher scores on Agreeableness (p = 0.020) and Conscientiousness (p = 0.006) than participants with AA or AG genotypes. These results suggest that older adults with higher COMT enzymatic activity (GG), therefore lower dopamine level, have lower Neuroticism scores, and higher Agreeableness and Conscientiousness scores. This is consistent with a recent model of phasic and tonic dopamine release suggesting that even though GG genotype is associated with lower tonic dopamine release, the phasic release of dopamine might be optimal for a more adaptive personality profile.

How Can Evolutionary Psychology Successfully Explain Personality and Individual Differences?

Although evolutionary psychology has been successful in explaining some species-typical and sex-differentiated adaptations, a large question that has largely eluded the field is this: How can the field successfully explain personality and individual differences? This article highlights some promising theoretical directions for tackling this question. These include life-history theory, costly signaling theory, environmental variability in fitness optima, frequency-dependent selection, mutation load, and flexibly contingent shifts in strategy according to environmental conditions. Tackling the explanatory question also requires progress on three fronts: (a) reframing some personality traits as forms of strategic individual differences; (b) providing a nonarbitrary, evolutionary-based formulation of environments as distributions and salience profiles of adaptive problems; and (c) identifying which strategies thrive and which falter in these differing problem-defined environments.

Combined epigenetic and intraspecific variation of the DRD4 and SERT genes influence novelty seeking behavior in great tit Parus major

DNA methylation is one of the main epigenetic mechanisms that can regulate gene expression and is an important means for creating phenotypic variation. In the present study, we performed methylation profiling of 2 candidate genes for personality traits, namely DRD4 and SERT, in the great tit Parus major to ascertain whether personality traits and behavior within different habitats have evolved with the aid of epigenetic variation. We applied bisulphite PCR and strand-specific sequencing to determine the methylation profile of the CpG dinucleotides in the DRD4 and SERT promoters and also in the CpG island overlapping DRD4 exon 3. Furthermore, we performed pyrosequencing to quantify the total methylation levels at each CpG location. Our results indicated that methylation was ∼1-4% higher in urban than in forest birds, for all loci and tissues analyzed, suggesting that this epigenetic modification is influenced by environmental conditions. Screening of genomic DNA sequence revealed that the SERT promoter is CpG poor region. The methylation at a single CpG dinucleotide located 288 bp from the transcription start site was related to exploration score in urban birds. In addition, the genotypes of the SERT polymorphism SNP234 located within the minimal promoter were significantly correlated with novelty seeking behavior in captivity, with the allele increasing this behavior being more frequent in urban birds. As a conclusion, it seems that both genetic and methylation variability of the SERT gene have an important role in shaping personality traits in great tits, whereas genetic and methylation variation at the DRD4 gene is not strongly involved in behavior and personality traits.

The Evolutionary Logic of the Obsessive Trait Complex: Obsessive Compulsive Personality Disorder as a Complementary Behavioral Syndrome

Freud noted that the obsessive traits of orderliness, parsimony, and obstinacy incontestably belonged together. This observation has been unfailingly justified, but unsatisfactorily explained. Being a highly heritable pattern essentially unaffected by parental influence, it is counterfactual to continue to explain the obsessive trait constellation as a pathological signature of harsh, authoritarian parenting. Alternatively, the present paper, building upon a previously promulgated evolutionary etiological model, describes how obsessive traits work in unison to enable survival within harsh northerly climates. What appears to be a loosely federated inventory of pathology, after the application of evolutionary reasoning, becomes a coherent behavioral package, adaptive suite, or behavioral syndrome. All three of these terms, taken from behavioral biology, suggest that traits strategically covary, such that the adaptive value of each trait is enhanced by the presence of the others. In this vein, the union of anxious tension and conscientiousness drives the obsessive personality to labor incessantly. The fruits of obsessive labor are then conserved through parsimoniousness, hoarding, vigilance, and niggardliness. And so, obsessive personality is a coherent behavioral package in that the drive to work towards the acquisition of necessities is paired with the drive to conserve and defend them.