Chapter 1. Nature and Nurture Effects On Childrens Outcomes : What Have We Learned From Studies of Twins And Adoptees There is a rich history of using data from twins and from adoptees to control for genetic influences and thereby examine the impact of environment on childrens outcomes. The behavioral genetics model is the workhorse of this literature and for a variety of outcomes including IQ scores and personality measures behavioral geneticists find that the bulk of the variance that can be explained is correlated with genetic influences. However finding that variation in test scores has a large genetic component is quite different than asking whether test scores can be improved by interventions and changes in policy or whether such interventions pass a cost benefit test. Economists have recently begun asking how the intergenerational transmission of educational attainment income and health vary when a child is being raised by adoptive rather than biological parents. Results suggest that both the biological and the nurturing parents contribute a great deal to the transmission of income and education to their children