Mental development: Family environment and genetic influences

A comprehensive home assessment was performed for 116 families whose twins were participants in a longitudinal study of early mental development. A large number of rating and observations made by a social worker during the home visit were condensed via factor analysis into four primary scores: adequacy of the home environment, maternal temperament, maternal cognitive skills, and maternal social-affect. The HOME scales of Caldwell (1978) were also completed, and all scores were combined with previously obtained measures of parental education and socioeconomic status. These scores were entered into a multiple regression analysis as predictors of off-spring mental development at 4 criterion ages: 6 months, 24 months, 3 years, and 6 years. The relationship was very weak at 6 months, but improved steadily over ages until reaching R_mult = .66 at 6 years. The four primary scores listed above plus father education all contributed significantly to the prediction of 6-year IQ scores, making it evident that home/family variables were substantially related to early mental development. However, a subsequent analysis using only parental education and SES as predictors yielded R_mult = .59. The qualitative features of home and mother thus appeared to augment a core linkage between parents and offspring representing intrinsic capabilities. The results are discussed in terms of both heritage and home environment as contributors to early mental development.