Maria Konnikova in Smithsonian:
In 1884, at his specially built Anthropometric Laboratory in London, Sir Francis Galton charged visitors three pence to undergo simple tests to measure their height, weight, keenness of sight and “swiftness of blow with fist.” The laboratory, later moved to the South Kensington Museum, proved immensely popular—“its door was thronged by applicants waiting patiently for their turn,” Galton said—ultimately collecting data on some 17,000 individuals. One measure that deeply interested Galton, who is recognized as “the father of psychometrics” for his efforts to quantify people’s mental abilities (and scorned as the founder of the eugenics movement because of his theories about inheritance), was speed. He believed that reaction time was one proxy for human intelligence. With a pendulum-based apparatus for timing a subject’s response to the sight of a disc of paper or the sound of a hammer, Galton collected reaction speeds averaging around 185 milliseconds, split seconds that would become notorious in the social sciences. For decades other researchers pursued Galton’s basic idea—speed equals smarts. While many recent tests have found no consistent relationship, some have demonstrated a weak but unmistakable correlation between short reaction times and high scores on intelligence tests. If there is a logic to the link, it’s that the faster nerve signals travel from your eyes to the brain and to the circuits that trigger your motor neurons, the faster your brain processes information it receives, and the sharper your intellect.
Psychologist Michael Woodley of Umea University in Sweden and his colleagues had enough confidence in the link, in fact, to use more than a century of data on reaction times to compare our intellect with that of the Victorians. Their findings call into question our cherished belief that our fast-paced lives are a sign of our productivity, as well as our mental fitness. When the researchers reviewed reaction times from 14 studies conducted between the 1880s and 2004 (including Galton’s largely inconclusive data set), they found a troubling decline that, they calculated, would correspond to a loss of an average of 1.16 IQ points a decade. Doing the math, that makes us mentally inferior to our Victorian predecessors by about 13 IQ points.
More here.