Tuesday, February 28, 2012


Almost 20 years ago, Richard Herrnstein and Charles Murray argued that social position was becoming more closely connected to intelligence.  According to their argument,  at one time many bright children from working-class families had to quit school for economic reasons (and in many cases, because they knew they would face racial and ethnic discrimination if they tried to keep going).   Most of them wound up in working-class or lower-middle class jobs.  That left managerial and professional jobs open to be taken by people who weren't particularly bright, but came from the right background.   With wider access to education and less discrimination, bright children from working-class backgrounds move up, and dullards from upper-class backgrounds move down.  That may seem like a good thing, but they argued it has some undesirable consequences.  Their book got a lot of criticism, but almost all of that focused on a different point--their claims about racial differences in intelligence.  Most people seemed to find their argument about class and intelligence to be pretty plausible.

At about the same time, I published a paper (with Julia McQuillan and Tracy Schauer) that suggested that class differences in intelligence were decreasing, not increasing.  The General Social Survey includes a ten-item vocabulary test, and vocabulary scores have a high correlation with scores on full-scale intelligence tests.  The decline was mostly because overall differences in vocabulary were declining--that is, people were coming to be more concentrated in the middle, with fewer high or low scores.

Now Charles Murray is back with the same argument, and this time it's getting more attention.  Meanwhile the GSS has kept accumulating more data.   Here are the means and standard deviations of vocabulary scores for people born in different decades:

            Mean     SD     N
1885-94     4.86    2.34     80
1895-1904   5.54    2.41    460
1905-1914   5.67    2.40   1251
1915-1924   5.95    2.30   2306
1925-1934   6.09    2.21   2529
1935-1944   6.25    2.18   3440
1945-1954   6.33    2.11   5119
1955-1964   5.90    2.06   4999
1965-1974   5.65    1.95   2746
1985-1984   5.69    1.85   1039
1985-1994   5.25    1.87    165

The standard deviations are smaller in more recent generations.  Of course, some of that may involve changes as people age.   But if you compare years in the GSS (1974 to 2008), there's still a decline.  That is, people in general have been getting more similar in terms of vocabulary knowledge.   But what about class differences?  I'll look at that in my next post.

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