PROMOTING POTENTIAL 295ity of individuals, the variation has little, if anything, to do with ge ne-
tics. Moreover, it is also worth remembering that IQ is not a mea sure of
general intelligence. It is a mea sure of rather special learning, associated
with social class and cultural background. And educational achievement
is not a “test” of potential, as I explain in chapter 11.
As explained earlier, though, many of the basic presuppositions under-
lying the concepts of genes in these proposals are also to be found in
conceptions of the environment. Th ese concepts, and alternatives to
them, take up most of the rest of this chapter.THE ENVIRONMENTResearch into environmental eff ects has been much more abundant
than that into ge ne tic eff ects. Th is is no doubt because environmental
interventions are superfi cially easier to implement than ge ne tic interven-
tions. Also, in the nature- nurture (part genes, part environments) frame-
work, even the higher heritability estimates for IQ or school achievement
leave scope for environmental intervention (however much the herita-
bility concept is misinterpreted).
My fi rst aim here is to illustrate conceptions of the environments
thought to cause diff erences in the development of potential (cognitive
abilities and school attainments). I describe the causal model(s) as-
sumed and how they imply the kinds of interventions construed. As we
shall see, most studies have been exploratory, with some imprecision
about the defi nition of environments as well as of eff ects. Some are highly
suggestive of real causes and fruitful interventions. Most are revealing
about the under lying concepts of the environment (on which I comment
below).
Because of the volume and diversity of such studies, this review is far
from exhaustive. I merely illustrate studies in a few broad categories
according to their scope and specifi city: chiefl y making a distinction
between the simpler material environments and the more complex socio-
psychological environments. Cutting across that breakdown is whether
the focus is on positive or negative consequences of the environment on
development, and whether it aff ects bodily or mental traits or both. As
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