Literacy and IQ
Marks (2010) published a new explanation of why IQ scores systematically vary across time, race and nationality. Marks (2010) hypothesizes that IQ differences across time, race and nationality are all caused by differences in literacy. Intelligence test performance requires literacy skills not present in all people to the same extent. In eight different analyses mean full scale IQ and literacy scores yielded correlations ranging from .79 to .99. Racial differences in IQ and the Flynn effect both have a similar explanation: literacy differences across race and across time could be the cause of both. Racial IQ differences are converging as the literacy skills within two populations become more equal. Thus racial differences have an environmental cause, just like the Flynn effect.
Read more about this topic: David Marks (psychologist)