The following talk, by James Flynn, has some bearing on the question.
Over the last century average scores on intelligence tests have increased dramatically. Flynn discusses the significance of this, and points to some implications of the influence of a persons educational achievements on their performance on intelligence tests.
James Flynn,
Why our IQ levels are higher than our grandparents':
https://www.youtube.com/watch?v=9vpqilhW9uI
Edited 5/7/2018 02:46:27