ABSTRACT
This chapter presents some closing thoughts on the key concepts discussed in the preceding chapters of this book. The book suggests that the importance and value of such interventions is incontestable, whatever may be the heritability of intelligence as traditionally measured. To the extent there is a heredity-environment paradox, it appears to be due to their still profound lack of understanding as to what variables substantially affect intellectual abilities, and as to how these effects take hold. The book shows environmental effects in the way. When one starts with dependent variables such as weight or Intelligence Quotient (IQ), the environmental effects appear to be far more powerful than when they start with specific independent variables and try to concatenate their effects. Analyses of the relative contributions of heredity and environment to intellectual functioning typically yield relatively high coefficients of heritability, often in the 0.4 to 0.8 range, with heritability increasing as a function of age.
