Frank M. Spinath

Twins Early Development Study (TEDS): A Multivariate, Longitudinal Genetic Investigation of Language, Cognition and Behavior Problems in Childhood.

The Twins Early Development Study (TEDS) focuses on the early development of the three most common psychological problems in childhood: communication disorders, mild mental impairment and behavior problems. The TEDS twins were assessed longitudinally at 2, 3, 4 and 7 years of age in order to investigate genetic and environmental contributions to change and continuity in language and cognitive development; it is multivariate in order to examine the origins of comorbidity; and it uses a large sample in order to study abnormal development in the context of normal development. The twins were identified from birth records of twins born in the UK in 1994-96. More than 15,000 pairs of twins have been enrolled in TEDS and the participating families are representative of the UK. The measures at 2, 3 and 4 years are administered by parents. At 7 years, children are assessed for language and cognitive development using telephone testing, parents and children are interviewed about behavior problems, and teachers also assess behavior problems as well as academic achievement. One set of findings is that the same genes largely contribute to both language and cognitive problems and the same genes affect normal and abnormal development, a result that suggests that general impairment may be a better target for genetic research than specific language impairment independent of nonverbal cognitive problems. DNA has been obtained so far for more than 4000 pairs and is being used initially in molecular genetic studies of language problems and hyperactivity.

Thin Slices of Behavior as Cues of Personality and Intelligence

Self-reports, peer reports, intelligence tests, and ratings of personality and intelligence from 15 videotaped episodes were collected for 600 participants. The average cross-situational consistency of trait impressions across the 15 episodes was .43. Shared stereotypes related to gender and age were mostly accurate and contributed little to agreement among judges. Agreement was limited mainly by nonshared meaning systems and by nonoverlapping information. Personality inferences from thin slices of behavior were significantly associated with reports by knowledgeable informants. This association became stronger when more episodes were included, but gains in prediction were low beyond 6 episodes. Inferences of intelligence from thin slices of behavior strongly predicted intelligence test scores. A particularly strong single predictor was how persons read short sentences.

Intelligence: Genetics, Genes, and Genomics.

More is known about the genetics of intelligence than about any other trait, behavioral or biological, which is selectively reviewed in this article. Two of the most interesting genetic findings are that heritability of intelligence increases throughout the life span and that the same genes affect diverse cognitive abilities. The most exciting direction for genetic research on intelligence is to harness the power of the Human Genome Project to identify some of the specific genes responsible for the heritability of intelligence. The next research direction will be functional genomics--for example, understanding the brain pathways between genes and intelligence. Deoxyribonucleic acid (DNA) will integrate life sciences research on intelligence; bottom-up molecular biological research will meet top-down psychological research in the brain.

Is the genetic structure of human personality universal? A cross-cultural twin study from North America, Europe, and Asia.

This study examined whether universality of the 5-factor model (FFM) of personality operationalized by the Revised NEO Personality Inventory is due to genetic influences that are invariant across diverse nations. Factor analyses were conducted on matrices of phenotypic, genetic, and environmental correlations estimated in a sample of 1,209 monozygotic and 701 dizygotic twin pairs from Canada, Germany, and Japan. Five genetic and environmental factors were extracted for each sample. High congruence coefficients were observed when phenotypic, genetic, and environmental factors were compared in each sample as well as when each factor was compared across samples. These results suggest that the FFM has a solid biological basis and may represent a common heritage of the human species.

Genetics of intelligence

This article provides an overview of the biometric and molecular genetic studies of human psychometric intelligence. In the biometric research, special attention is given to the environmental and genetic contributions to specific and general cognitive ability differences, and how these differ from early childhood to old age. Special mention is also made of multivariate studies that examine the genetic correlation between intelligence test scores and their correlates such as processing speed, birth weight and brain size. After an overview of candidate gene associations with intelligence test scores, there is a discussion of whole-genome linkage and association studies, the first of which have only recently appeared.

Genetics and general cognitive ability (g)

Two recent articles in this journal made the case for the existence and importance of g and reviewed research on cognitive and psychophysical correlates of psychometric g. This review considers g from a genetic perspective. Multivariate genetic research indicates that g accounts for nearly all of the genetic variance of diverse psychometric cognitive tests (genetic g). Recent research suggests not only that elementary cognitive tasks are genetically linked to psychometric g but also that genetic g pervades these tasks. Contrary to the assumption of modularity that dominates cognitive science, genetic g exists in the mind as well as in psychometric tests.

The serotonin transporter gene and peer-rated neuroticism

POLYMORPHISMS in the serotonin transporter gene (5HTT) have been reported to be associated with neuroticism (emotionality) and with depression. A recent report of an association between 5HTT and neuroticism involved unselected samples and self-report questionnaires.1 We attempted to extend these findings using a selected extremes design and peer ratings. From a sample of 2085 individuals, each assessed on neuroticism by two independent peers, we selected 52 individuals from the top 5% and 54 individuals from the bottom 5%. No association was found for either a functional 44 bp insertion/deletion polymorphism in 5HTT regulatory sequence (5HTTLPR) or for a non-functional variable number tandem repeat 5HTT polymorphism.

Patterns and Sources of Adult Personality Development: Growth Curve Analyses of the NEO PI-R Scales in a Longitudinal Twin Study

The present study examined the patterns and sources of 10-year stability and change of adult personality assessed by the 5 domains and 30 facets of the Revised NEO Personality Inventory. Phenotypic and biometric analyses were performed on data from 126 identical and 61 fraternal twins from the Bielefeld Longitudinal Study of Adult Twins (BiLSAT). Consistent with previous research, LGM analyses revealed significant mean-level changes in domains and facets suggesting maturation of personality. There were also substantial individual differences in the change trajectories of both domain and facet scales. Correlations between age and trait changes were modest and there were no significant associations between change and gender. Biometric extensions of growth curve models showed that 10-year stability and change of personality were influenced by both genetic as well as environmental factors. Regarding the etiology of change, the analyses uncovered a more complex picture than originally stated, as findings suggest noticeable differences between traits with respect to the magnitude of genetic and environmental effects.

Association analysis of MAOA and COMT with neuroticism assessed by peers.

There are several reported associations between depressive disorders, panic disorder, and obsessive–compulsive disorder (OCD) and a variety of polymorphisms in the monoamine oxidase A (MAOA) gene. Associations have also been reported between the catechol‐O‐methyltransferase (COMT) gene and both OCD and bipolar depression. However, the role of these markers has not been explored for the personality trait of neuroticism (N), a normally distributed quantitative trait, which is highly genetically correlated with anxiety and depression and may be a vulnerability to either type of disorder. We explored the possible role of MAOA, COMT, and their interaction on N using a selected extremes design. From a sample of 2,085 individuals, each assessed for N by two independent peers rather than using self‐report questionnaires, we selected 57 individuals from the top 10% of scores, and 62 individuals from the bottom 10%. Using selected extreme low subjects as the controls, rather than an unselected control group gives roughly twice the power of a standard case‐control design. We typed a functional variable number tandem repeat (VNTR) in the MAOA gene promoter, and a functional polymorphism in the coding region of the COMT gene. Two novel alleles in the MAOA VNTR were identified on the basis of their size, and their structure examined by sequencing analysis. We found weak evidence for association with COMT genotype, when the females and males were considered separately, and for MAOA genotype in males only. There was no significant interaction between COMT and MAOA.

Genetic and Environmental Influences on Observed Personality: Evidence From the German Observational Study of Adult Twins

Previous behavior-genetic research on adult personality relied primarily on self-reports or peer reports that may be subject to contrast effects, resulting in biased estimates of genetic and environmental influences. In the German Observational Study of Adult Twins (GOSAT), personality traits of 168 monozygotic (MZ) and 132 dizygotic (DZ) twin pairs were rated on 35 adjective scales, largely markers of the Big 5. The ratings were provided by 120 judges who never met the twins but observed videotaped behaviors of 1 twin of each pair in 1 of 15 different settings. The aggregated video-based trait ratings were highly reliable, and substantial correlations were obtained between MZ as well as DZ twins. Model-fit analyses suggested about 40% genetic, 25% shared environmental, and 35% nonshared environmental influence. Extraversion was the only trait that seemed not to be influenced by shared environment.