A long-term rise and recent decline in intelligence test performance: The Flynn Effect in reverse

Thomas Teasdale and David Owen: In the 1980s reviewed evidence indicated that, through the preceding decades of the last century, population performance on intelligence tests had been rising substantially, typically about 3–5 IQ points per decade, in developed countries. The phenomenon, now termed the ‘Flynn Effect’, has been variously attributed to biological and/or to social…

via A long-term rise and recent decline in intelligence test performance: The Flynn Effect in reverse — Schoolinfosystem.org