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.