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The IQ Paradox: Still Resolved

William T. Dickens and James R. Flynn

Published in Psychological Review, Vol. 109 #4 (2002)


In our original paper we formalized the consensus model that environment affects
IQ and IQ affects environment and showed that it can resolve the apparent paradox
between high heritability and large environmental effects. Our commentators suggest that
that model has undesirable properties which call its usefulness into question. Loehlin
argues that IQ is persistent and that incorporating persistence into the model causes
problematic behavior. Rowe and Rodgers argue that an increasing correlation of IQ and
environment should have caused growing variance of IQ. Empirical evidence suggests
that IQ is not sufficiently persistent to cause the problems Loehlin finds and that the
correlation of IQ and environment has not grown much over time so that the reciprocal
effects model need not imply increasing variance.

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