Stability and structure of infant and toddler temperament in two longitudinal studies in Germany

The present study investigated the factor structure and longitudinal stability of infant and toddler temperament measured with the Infant Behavior Questionnaire-Revised (IBQ-R) and the Early Childhood Behavior Questionnaire (ECBQ) in two German samples. Since the few studies using the German IBQ-R failed to replicate the commonly assumed three factors of infant temperament, another exploration of its factor structure was necessary. Whereas previous stability measurements are usually based on groups with relatively large age ranges, we investigated stability between concrete ages. In Study 1, the IBQ-R was applied in 9- and 12-month-old infants. In Study 2, both questionnaires were applied in 12-, 18-, and 24-month-olds. Factor analyses of the IBQ-R in both studies revealed a two-factor solution comprising Surgency/ Extraversion and Negative Affectivity, replicating earlier findings with German infants. The Orienting/ Regulation factor was not replicated for the IBQ-R, whereas analysis of the ECBQ revealed a three-factor solution for toddlers. The results showed stability of temperament ratings within infancy (Study 1) and toddlerhood (Study 2) as well as between the developmental periods within the second year of life (Study 2). Taken together, the present findings indicate that temperament stability emerges early in life and can be reliably measured using the IBQ-R and ECBQ, whereas the factor structure of temperament in infancy requires further validation.

Parental genetic contributions to neonatal temperament in a nonhuman primate (Macaca mulatta) model

Temperament is an individual's nature and is widely believed to have a heritable foundation. Few studies, however, have evaluated paternal and maternal contributions to the triadic dimensions of temperament. Rhesus monkeys are widely utilized to model genetic contributions to human development due to their close genetic-relatedness and common temperament structure, providing a powerful translational model for investigating paternal and maternal genetic influences on temperament. The temperament of rhesus monkey infants born to 19 different sires and 50 different dams was assessed during the first month of life by comparing the temperament of paternal or maternal half-siblings reared with their mothers in species-normative conditions or reared in a neonatal nursery. Factor scores from three dimensions of temperament were obtained (Orienting/Regulation, Negative Affectivity, and Surgency/Extraversion) and ANOVAs were used to assess genetic effects. For paternal half-siblings, results showed a statistically significant paternal contribution to Orienting/Regulation, Negative Affectivity, and Surgency/Extraversion factor scores. For maternal half-siblings, results showed a statistically significant contribution to Orienting/Regulation factor scores. When parsed by early rearing condition, results showed a paternal contribution Orienting/Regulation, Negative Affectivity, and Surgency/Extraversion scores for paternal half-siblings reared in the neonatal nursery, while there was only a paternal contribution to Surgency/Extraversion for paternal half-siblings reared by their mothers. There was only a maternal contribution to Orienting/Regulation for maternal half-siblings reared by their mothers. These results show that paternal and maternal contributions to temperament vary by environmental context, and that mothers may environmentally buffer their infants from paternal contributions to their temperament.