As long-time readers know, my independent research has found that the Flynn effect, when properly studied, has only been about 1 point a decade on the Wechsler in Northern America, and not 3 points a decade as Flynn had claimed.

But why should anyone believe me, a nobody blogger, over one of the greatest psychologists of the 20th century?

Because I’ve found some research in support of my claim. A study where the original WISC, which was normed in 1947, was given to a fairly representative sample of American kids circa 1967.

Source: Pasewark, R. A., Sawyer, R. N., Smith, E., Wasserberger, M., Dell, D., Brito, H., & Lee, R. (1967). Concurrent Validity of the French Pictorial Test of Intelligence. The Journal of Educational Research, 61(4), 179–183.

If the Flynn effect were 3 points a decade, we’d expected kids tested on a 20-year-old test to average 6 points above the U.S. mean of 100, but instead they only averaged 3 points above 100, consistent with a Flynn Effect of 1.5 points per decade.

Source: Pasewark, R. A., Sawyer, R. N., Smith, E., Wasserberger, M., Dell, D., Brito, H., & Lee, R. (1967). Concurrent Validity of the French Pictorial Test of Intelligence. The Journal of Educational Research, 61(4), 179–183.