Scientific Reasoning Explains Increases in IQ

The bombshell is that the Flynn Effect is almost certainly environmental. Natural selection has a speed limit measured in generations, but the Flynn Effect is measurable on the scale of decades and years. Flynn was also able to rule out increases in nutrition, overall health, and outbreeding (marrying outside one’s local community) as explanations for his eponymous effect.241 Whatever propels the Flynn Effect, then, is likely to be in people’s cognitive environments, not in their genes, diets, vaccines, or dating pools.

A breakthrough in the mystery of the Flynn Effect was the realization that the increases are not gains in general intelligence.242 If they were, they would have lifted the scores on all the subtests, including vocabulary, math, and raw memory power, with a rate related to the degree each test correlates with g. In fact the boost was concentrated in subtests like Similarities and Matrices. Whatever the mystery factor in the environment may be, it is highly selective in the components of intelligence it is enhancing: not raw brainpower, but the abilities needed to score well on the subtests of abstract reasoning.

The best guess is that the Flynn Effect has several causes, which may have acted with different strengths at different times in the century. The improvements on visual matrices may have been fueled by an increasingly high-tech and symbol-rich environment that forced people to analyze visual patterns and connect them to arbitrary rules.243 But proficiency with visuals is a sideshow to understanding the gains in intelligence that might be relevant to moral reasoning. Flynn identifies the newly rising ability as postscientific (as opposed to prescientific) thinking.244 Consider a typical question from the Similarities section of an IQ test: “What do dogs and rabbits have in common?” The answer, obvious to us, is that they are both mammals. But an American in 1900 would have been just as likely to say, “You use dogs to hunt rabbits.” The difference, Flynn notes, is that today we spontaneously classify the world with the categories of science, but not so long ago the “correct” answer would seem abstruse and irrelevant. “ ‘Who cares that they are both mammals?’ ” Flynn imagines the test-taker asking in 1900. “That is the least important thing about them from his point of view. What is important is orientation in space and time, what things are useful, and what things are under one’s control.”

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Flynn suggests that over the course of the 20th century, scientific reasoning infiltrated from the schoolhouse and other institutions into everyday thinking. More people worked in offices and the professions, where they manipulated symbols rather than crops, animals, and machines. People had more time for leisure, and they spent it in reading, playing combinatorial games, and keeping up with the world. And, Flynn suggests, the mindset of science trickled down to everyday discourse in the form of shorthand abstractions. A shorthand abstraction is a hard-won tool of technical analysis that, once grasped, allows people to effortlessly manipulate abstract relationships. Anyone capable of reading this book, even without training in science or philosophy, has probably assimilated hundreds of these abstractions from casual reading, conversation, and exposure to the media, including proportional, percentage, correlation, causation, control group, placebo, representative sample, false positive, empirical, post hoc, statistical, median, variability, circular argument, tradeoff, and cost-benefit analysis. Yet each of them—even a concept as second-nature to us as percentage—at one time trickled down from the academy and other highbrow sources and increased in popularity in printed usage over the course of the 20th century.