Feeling inhibited and socially not at ease is reflected in the trait social inhibition (SI). SI is associated with psychopathology that arises in young adulthood, such as anxiety. We aim for a better insight into the genetic and environmental contributions to SI across the life span, and as such examine their contributions to SI stability and…

Longitudinal data from a large sample of twins participating in the Netherlands Twin Register (n = 42,827, age range 3-16) were analyzed to investigate the genetic and environmental contributions to childhood aggression. Genetic auto-regressive (simplex) models were used to assess whether the same genes are involved or whether new genes come into…

In the present study, we investigated genetic and environmental effects on motor impulsivity from childhood to late adolescence using a longitudinal sample of twins from ages 9 to 18 years. Motor impulsivity was assessed using errors of commission (no-go errors) in a visual go/no-go task at 4 time points: ages 9-10, 11-13, 14-15, and 16-18 years.…

In this review, we evaluate developmental and personality research with the aim of determining whether the personality trait of conscientiousness can be identified in children and adolescents. After concluding that conscientiousness does emerge in childhood, we discuss the developmental origins of conscientiousness with a specific focus on…

This study investigated the mean-level and individual-level trends as well as the genetic and environmental sources of rank-order continuity and change in temperament traits ("Briskness, Perseveration, Sensory Sensitivity, Emotional Reactivity, Endurance, and Activity"). We analyzed self-reports and peer ratings from 2 adult age groups…

Behaviors of monozygotic and dizygotic twins that were indicative of wariness were observed when the twins were 14, 20, and 24 months of age. An index of inhibition constructed from observations showed internal consistency at all ages and stability across ages. Heritability was a factor at all ages. (BC)

Scores on a mental development scale were correlated for 8-month-old twins and other sibling pairs. Greater correlations were found between twins than sibling pairs. (ST)

Observational measures of monozygotic and dizygotic twins' reactions to simulations of distress in others were obtained when the twins were 14 and 20 months old. Components of concern for others increased with age. Girls scored higher than boys on most measures. There was modest evidence for heritability of empathy. (BC)

The home environment of nonadoptive and adoptive sibling pairs was assessed using the Home Observation for Measurement of the Environment when each sibling was one and two years of age. Correlations between home environment scores for nonadoptive siblings were greater than those for adoptive siblings. (BC)

Parents of 30-month-old children were assessed on measures of affectivity, personality, and behavior. Parents of inhibited children showed lower extraversion, higher avoidance and shyness, and faster drawing times on a task that involved uncertainty than did parents of uninhibited children. (Author/BC)

In this paper, the relation between heritability and sources of group differences is analyzed in terms meaningful to the nonmathematician. (Author)

A twin analysis was applied to infants' social behavior in standardized situations that permitted the comparison of social responding to mother and a stranger in different contexts. Twenty-one identical twin pairs and twenty-five fraternal twin pairs were observed in their homes using time-sampled observations of specific behaviors. (Author/SS)

Two studies of twin, sibling, and cousin pairs among children attempted to extend a model, called DF analysis, which separates hereditary and shared environmental influences. First study supported the validity of DF analysis applied to kinship height and weight data. The second study showed that spanking, reading, and quality of home environment…

Examines genetic influences on language by assessing 158 preschool twins on vocabulary comprehension, semantic knowledge, morphology, syntax, and articulation. Vocabulary comprehension was significantly influenced by heredity, whereas performance skills were influenced by between-family environmental factors. (Author/AS)