ABSTRACT
The history of how American minds have adapted to social demands in the 20th century can be written only if the evaluation of IQ gains is distanced from g. The relationship between IQ gains and g can be clarified only if a causal scenario about the former is stated. Until now, I have been reluctant to endorse or state a causal scenario. However, the mathematical model of William T. Dickens (Dickens & Flynn, 2001) has made plausibility possible because it does two things: suggests how environmental change could be potent enough to cover the magnitude of IQ gains, and identifies a bridge between IQ gains and g that illuminates the significance of whether the two correlate or not. I should add that Dickens is not to be held responsible for the detail of the scenario I offer or the implications drawn herein. The scenario has two dominant themes: the industrial revolution as the creator of exogenous causes, and the reciprocal causality of IQ and environment as the multiplier of effects. The latter requires some explanation.
