The hypothesis that enhanced nutrition is mainly responsible for massive IQ gains over time borrows plausibility from the height gains of the 20th century. However, evidence shows that the two trends are largely independent. A detailed analysis of IQ trends on the Raven's Progressive Matrices tests in Britain dramatizes the poverty of the nutrition hypothesis. A multiple factor hypothesis that operates on three levels is offered as an alternative instrument of causal explanation. The Raven's data show that over the 65 years from circa 1942 to the present, taking ages 5-15 together, British school children have gained 14 IQ points for a rate of 0.216 points per year. However, since 1979, gains have declined with age and between the ages of 12-13 and 14-15, small gains turn into small losses. This is confirmed by Piagetian data and poses the possibility that the cognitive demands of teen-age subculture have been stagnant over perhaps the last 30 years.
Download Info
To download:
If you experience problems downloading a file, check if you have the
proper application to
view it first. Information about this may be contained
in the File-Format links below. In case of further problems read
the IDEAS help
page. Note that these files are not on the IDEAS
site. Please be patient as the files may be large.
As the access to this document is restricted, you may want to look for a different version under "Related research" (further below) or search for a different version of it.