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Encyclopedia of Psychology Alan E. Kazdin, PhD, Editor-in-Chief

BEHAVIORAL GENETICS

A variant espoused by Konrad Lorenz in classical ethology maintains that a complex behavior consists of components, each of which derives exclusively from either G or E, resulting in learning-instinct intercalation. This view is rare in behavior genetics and is regarded as a relic by many modern ethologists as well.

Two of these perspectives are sometimes joined in chimeric theories. For example, Sandra Scarr (Child Development, 1992, 63, 1-19) asserts that within the range of environments commonly encountered in society, individual variation arises mainly from genetic variation (the G + E view), whereas in extremely poor environments the expression of genetic individuality may be suppressed (interactionism). The hardware/software or computer model argues that genes provide a code or program for brain development (G versus E) and hardwired neural structures then determine the sensitivity of the individual to variations in the environment or the ease of modifying behavior by experience (a form of interactionism termed the norm of reaction).

It is now widely recognized by geneticists that a characteristic that appears heritable may also be substantially modifiable in a new environment. Nevertheless, two nongeneticists, Richard Herrnstein and Charles Murray (The Bell Curve, New York. 19~4re)su rrected the discredited claim that high heritability of IQ makes aid to the poor futile, and they proposed instead that eugenic measures be implemented to enhance national intelligence

It is essential that we learn how many interacting molecular parts are pertinent to a neural or psychological process. It is already apparent that several hundred genes are involved in the operation of merely one synapse between two neurons, and it seems likely that several thousand genes at the very minimum are active in a moderately complex tissue such as the hippocampus or cerebellum.

To date, no gene influencing intelligence, personality, sexual orientation, alcoholism, or schizophrenia has been rigorously verified. At the same time, many mutations are known that lead to relatively rare and gross deficits. Now the big question is whether genes with moderate effects of greater interest to the psychology of individual differences will be detectable.

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