Beyond Heritability
As illustrated so far, most psychology researchers
are in agreement that heredity and environment both
play significant roles in the development of various
human traits. Researchers may disagree, however, on
the extent to which heredity and environment con-
tribute to the development of a particular dimension,
and on how various factors may affect each other to
create a certain human characteristic. Neither herita-
bility estimates nor concordance rates provide useful
information on the latter type of disagreement: how
various hereditary and environmental factors interact
with each other to result in a particular characteristic.
Mental health, education, and applied psychology re-
searchers are especially concerned about optimizing
the developmental outcomes among people from all
backgrounds. To this end, knowing that there is a .86
heritability estimate for IQ scores among identical
twins, for example, is not particularly helpful in terms
of establishing ways of maximizing the life choices
and opportunities for individuals. In attaining such
goals, it is crucial to understand how various factors
relate to each other. Naturally, in order to do so, one
must first identify which factors are involved in the
development of a given trait. Unfortunately, re-
searchers have had very limited success in identifying
specific genetic patterns that influence particular psy-
chological and behavioral characteristics.
Nevertheless, this is not to suggest that one
should ignore the role of heredity as reflected in heri-
tability estimates altogether and focus on optimizing
the environmental factors for every child. Heredity,
as has been examined, undoubtedly contributes to the
development of various human traits. Also, research-
ers exploring environmental influences have found
that contrary to what most theorists expected, envi-
ronmental factors that are shared by reared-together
twins do not appear to be relevant in explaining the
development of particular traits. It is therefore un-
likely that exposing every child to a ‘‘one size fits all’’
environment designed to foster a particular trait,
would benefit everyone equally. Some may react fa-
vorably to such an environment, while others may not
react to it at all; there may be yet others who react
negatively to the same environment. The notion of
‘‘range of reaction’’ helps us conceptualize the com-
plex relationship between heredity and environment;
people with varying genetically influenced predispo-
sitions respond differently to environments. As sug-
gested by Douglas Wahlsten in a 1994 article in
Canadian Psychology, an identical environment can
elicit different reactions in different individuals, due
to variations in their genetic predispositions. In a hy-
pothetical scenario, Wahlsten suggested that increas-
ing intellectual stimulation should help increase
cognitive performances of some children. Moderate,
rather than high, levels of intellectual stimulation
may, however, induce optimal cognitive perfor-
mances in others. By contrast, the same moderate le-
vels of stimulation may actually cause some children
to display cognitive performances that are even worse
than how they performed in a minimally stimulating
environment. In addition, the ‘‘optimal’’ or ‘‘mini-
mal’’ performance levels may be different for various
individuals, depending on their genetic makeup and
other factors in their lives. This example illustrates
the individual differences in ranges of reaction; there
is no ‘‘recipe’’ for creating environments that facili-
tate the development of particular characteristics in
everyone. Heredity via environment, rather than he-
redity versus environment, therefore, may better char-
acterize this perspective.
These views are consistent with the 1990s’ back-
lash against the view that was prevalent in the mid- to
late twentieth century among many clinical psycholo-
gists, social workers, and educators, who focused sole-
ly on environmental factors while discounting the
contributions of hereditary factors. Among the theo-
ries they advocated were that gay males decidedly
come from families with domineering mothers and
no prominent masculine figures, that poor academic
performances result from lack of intellectual stimula-
tion in early childhood, and that autism stems from
poor parenting practices. Not surprisingly, empirical
data do not support these theories. Still, people often
continue to believe, to some extent, that proper envi-
ronments can prevent and ‘‘cure’’ these non-
normative characteristics, not realizing that heredity
may play significant roles in the development of these
traits.
Some scholars believe that this ‘‘radical environ-
mentalist’’ view found its popularity in the 1950s as
a reaction to racist Nazi thinking, which held that
some groups of individuals are genetically inferior to
others and that the undesirable traits they are per-
ceived to possess cannot be prevented or modified.
These assumptions are harmful, as they limit the op-
portunities for advancement of some people, strictly
because of their membership in a stigmatized group.
It is nevertheless important to reiterate that individu-
al differences, as opposed to group differences, in ge-
netic predispositions are evident in the development
of most emotional, behavioral, and cognitive traits.
With this in mind, it is also important to realize that
focusing on optimizing environmental influences
while ignoring hereditary influences may lead to the
neglect of the developmental needs of some individu-
als, and it may be just as harmful in some cases as fo-
cusing exclusively on hereditary influences.See also: PHENOTYPEHEREDITY VERSUS ENVIRONMENT 185