Age-Related Cognitive Decline and the Flynn Effect

July 2, 2009

    In 2009-6-26_My_Story, I stated that the age-related cognitive decline for someone transitioning from 25 to 75 would turn out to be more than 20 points of IQ (see below). Today, I revisited an article that I wrote in   

2004 examining the role of the Flynn Effect on Age-Related Cognitive Decline. The Flynn Effect refers to the discovery by psychologist James R. Flynn that IQ scores in at least 19 industrial nations have quietly been rising at the rate of about 3 points per decade for at least the past 100 years, or about 30 points during the 20th century. (For the past few days, I've been reading (and re-reading) Dr. Flynn's recent book, "What Is Intelligence?") To cut to the chase, IQ tests have had to gradually be made more difficult since the first popular IQ test, the 1916 edition of the Stanford-Binet, was standardized and released. What this means is that someone who scored an IQ of 100 on the 1937 Revision of the Stanford-Binet would only score about 80 on the latest (Fifth) Revision of the Stanford-Binet not because he or she were any less intelligent than they were in 1937 but because the bar on the Fifth Revision of the Stanford-Binet has been set that much higher than it was the Second (1937) revision of this test! When you apply this to the age-related cognitive decline shown in the above chart, you realize that practically all the "age-related cognitive decline" isn't a consequence of cognitive decline but of the fact that the Stanford-Binet has become that much more difficult. If you had taken the SB-5 at the age of 25, you wouldn't have scored significantly, if at all, higher on it than you would now at 75. The chart below shows the same information displayed in the chart above except that the chart below has been corrected for the Flynn Effect.

Clearly, there is no indication of true cognitive decline until one reaches one’s upper sixties, and then the slippage is moderate.