The Flynn Effect

The Flynn Effect is the name for the systematic rise in cognitive ability scores over generations.  In a recent (November 2021) study published in Child Development, Giangrade et al. report a study of 7-15-year-old twins, roughly half of whom are monozygotic twins, half dizygotic twins in the Louisville Twin Study. Data were collected from 1957 to 1999 using the WISC, WISC-R, and WISC III (as the Wechsler Intelligence Scale for Children changed). While they found both within- and between-subject effects, the overall gains were the equivalent of three IQ points per decade. They conclude that, “individual sensitivity to the Flynn Effect was moderated by an interplay of genetic and environmental factors.”

In the past, some of the environmental factors that may contribute have been nutrition and health care. Flynn has also suggested that the increase may be in abstract thinking skills as we have moved from an agricultural to industrial to information-based society. This may have important implications for psychologists who do diagnostic testing, especially as they communicate findings to clients, parents, and referral sources.