IQ gains over time: Toward finding the causes.

T chapter describes the magnitude, pattern, duration, and prev­ alence of IQ gains over time. Its u ltimate purpose is to suggest and evaluate research strategies that might generate promising causal hypotheses. However, the phenomenon to be explained dictates the task of explanatory hypotheses, which poses a fundamental question: Granted that people are better at taking IQ tests, what other, related cognitive skills are they better at? Estimates of the size of this package might range all the way from doing better at IQ tests plus some related cognitive skills too trivial to have significant realworld effects, to doing better on IQ tests plus all of the cognitive skills that are usually en­ hanced when one goes from a student with an IQ of 75 to a student at the next desk with an IQ of 100 or 125. My purposes dictate covering the following topics: describing and evidencing the brute phenomenon of IQ gains over time, discussing what other cognitive skil ls have es­ calated in tandem, using that discussion to critique the attempts at causal explanation made thus far, and suggesting research strategies that might engender better hypotheses. In addition, I discuss theoretical and practical implications of IQ gains when these issues seem significant enough to justify a digression.