Heredity versus Environment - 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 contribute to the development of a

particular dimension, and on how various factors may affect each other to

create a certain human characteristic. Neither heritability 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 researchers 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, researchers have had very limited success in

identifying specific genetic patterns that influence particular psychological

and behavioral characteristics.

Nevertheless, this is not to suggest that one should ignore the role of

heredity as reflected in heritability 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, researchers exploring environmental influences have found that

contrary to what most theorists expected, environmental factors that are

shared by reared-together twins do not appear to be relevant in explaining

the development of particular traits. It is therefore unlikely that exposing

every child to a "one size fits all" environment designed to foster a particular

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trait, would benefit everyone equally. Some may react favorably 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 complex relationship between heredity

and environment; people with varying genetically influenced predispositions

respond differently to environments. As suggested 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 hypothetical scenario, Wahlsten suggested that

increasing intellectual stimulation should help increase cognitive

performances of some children. Moderate, rather than high, levels of

intellectual stimulation may, however, induce optimal cognitive

performances in others. By contrast, the same moderate levels 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 "minimal" 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 facilitate the development of particular characteristics in

everyone. Heredity via environment, rather than heredity versus

environment, therefore, may better characterize this perspective.

These views are consistent with the 1990s' backlash against the view that

was prevalent in the mid- to late twentieth century among many clinical

psychologists, social workers, and educators, who focused solely on

environmental factors while discounting the contributions of hereditary

factors. Among the theories 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

stimulation in early childhood, and that autism stems from poor parenting

practices. Not surprisingly, empirical data do not support these theories.

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Still, people often continue to believe, to some extent, that proper

environments 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 perceived to possess cannot be prevented or

modified. These assumptions are harmful, as they limit the opportunities for

advancement of some people, strictly because of their membership in a

stigmatized group. It is nevertheless important to reiterate that individual

differences, as opposed to group differences, in genetic 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 individuals, and

it may be just as harmful in some cases as focusing exclusively on hereditary

influences.

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