Educability-and-Group-Differences-1973-by-Arthur-Robert-Jensen

234 Educability and Group Differences
probably fruitful environmental variables for experimental manipulation.
It is this approach which distinguishes research on environmental
factors, which is a legitimate scientific enterprise, from
dogmatic environmentalism. Behavior geneticists recognize the
influence of non-genetic factors in all forms of behavior and in all
individual and group differences, and they are interested in
understanding these non-genetic factors precisely and in learning
what proportions of the variance they contribute, singly and in
combination, and how much is due to additive, interactive, and
covariance effects in the population. Developmental behavior
genetics seeks to understand how the individual phenotype
develops through the genotype’s interaction with and utilization
of the environment. Variance in genotypes for any trait, within
or between groups, is not ruled out or restricted on any a priori
basis. Environmentalism, on the other hand, simply decrees the
null hypotheses a priori with respect to certain classes of genetic
variance, and in order to fill the void must posit a number of
environmental influences or measurement biases which often are
accepted merely on the grounds of plausibility. It is possible,
however, to bring research evidence to bear on many specific
environmental factors and test biases which environmentalists
assume are the main causes of subpopulation differences in
intelligence and related performance. Under such examination of
the relevant evidence, some of the main pillars of the environmentalist
argument regarding Negro-white intelligence differences
simply collapse, still others are seen to be resting on extremely
flimsy foundations in fact, while the remainder are so vaguely
formulated as to be insusceptible to empirical proof or disproof.