Bayesian Investor Blog

Book review: What is Intelligence?: Beyond the Flynn Effect by James Flynn
This book may not be the final word on the Flynn Effect, but it makes enough progress in that direction that it is no longer reasonable to describe the Flynn Effect as a mystery. I’m surprised at how much Flynn has changed since the last essay of his I’ve read (a somewhat underwhelming chapter in The Rising Curve (edited by Ulric Neisser)).
Flynn presents evidence of very divergent trends in subsets of IQ tests, and describes a good hypothesis about how that divergence might be explained by increasing cultural pressure for abstract, scientific thought that could create increasing effort to develop certain kinds of cognitive skills that were less important in prior societies.
This helps explain the puzzle of why the Flynn Effect doesn’t imply that 19th century society consisted primarily of retarded people – there has been relatively little change in how people handle concrete problems that constituted the main challenges to average people then. He presents an interesting example of how to observe cognitive differences between modern U.S. society and societies that are very isolated, showing big differences in how they handle some abstract questions.
He also explains why we see very different results for IQ differences over time from what we see when using tests such as twin studies to observe the IQ effects of changes in environment on IQ: the twin studies test unimportant things such as different parenting styles, but don’t test major cultural changes that distinguish the 19th century from today.
None of this suggests that the concept of g is unimportant or refers to something unreal, but a strong focus on g has helped blind some people to the ideas that are needed to understand the Flynn Effect.
Flynn also reports that the rise in IQs is, at least by some measures, fairly uniform across the entire range of IQs (contrary to The Bell Curve’s report that it appeared to affect mainly the low end of the IQ spectrum). This weakens one of the obvious criticisms of David Friedman’s conjecture that modern obstetrics caused the Flynn Effect by reducing the birth related obstacles to large skulls (although if that were the main cause of the Flynn Effect, I’d expect the IQ increase to be largest at the high end of the IQ spectrum).
It also weakens the inference I drew from Fogel’s book on malnutrition. Flynn does little to directly address Fogel’s argument that the benefits of improved nutrition show up with longer delays than most people realize, but he does report some evidence that the Flynn Effect continues even when the height increases that Fogel relies on to measure the benefits of nutrition stop.
Flynn reports that the Flynn Effect has probably stopped in Scandinavia but hasn’t shown signs of stopping in the U.S. His comments on the future of IQ gains are unimpressive.
There are a few disappointing parts of the book near the end where he wanders into political issues where he has relatively little expertise, and his relatively ordinary opinions are no better than a typical academic discussion of politics. In spite of that, the book is fairly short and can be read quickly.
One interesting experiment that Flynn discusses tested whether students preferred one dollar now or two dollars next week. The results were twice as useful in predicting their grades as IQ tests. Flynn infers that this is a test of self control. I presume that is part of what it tests, but I wonder whether it also tests whether the students were able to realize that the testers’ word could be trusted (due to better ability to analyze the relevant incentives? or due to a general willingness to trust strangers because of how the ways they met people selected for trustworthy people?).