Abstract
The genetic and environmental etiologies of covariation among measures of temperament (the Bayley Infant Behavior Record's Affect and Task Orientation Scales and the first principal component from the New York Longitudinal Study's difficult temperament items) and cognition (the Bayley Mental Development Index [MDI] and the total score on the Sequenced Inventory of Communication Development [SICD] were assessed at 24 months of age in 70 biologically related and 66 unrelated pairs of siblings in the Colorado Adoption Project. Between- and within-pair mean cross products were equated to expectations using the LISREL multiple-group specification (Fulker, Baker and Bock, 1983) to obtain maximum-likelihood estimates of genetic and environmental factor loadings and specific variances. The full one-factor model, with one general factor and five specific factors, provides a satisfactory fit to the data (χ 2 = 27.8, df = 30, P = 0.58). Genetic influences are important for the Bayley MDI and SICD languages measures, but not for temperament measures. Little or no evidence was found for shared-sibling environmental influences for any of the measures. Various hypotheses regarding genetic and environmental correlation structures were also tested.
Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
