Intelligence Is Still Not Fixed at Birth

Dr. Scott Barry Kaufman:

In 1932, the entire population of Scottish 11-year olds (87, 498 children) took an IQ test. Over 60 years later, psychologists Ian Deary and Lawrence Whalley tracked down about 500 of them and gave them the same test to take again. Here are the results:

Some things to note here. Firstly, the correlation is pretty high-- .66, to be exact. Those who were at the top of the pack at age 11 also tended to be at the top of the pack at age 80, and those who were at the bottom also tended to stay at the bottom. Secondly, the correlation is not perfect. A few outliers can be found. One person had an IQ of over 100 at age 11, but scored just over 60 at age 80. There are many possible reasons for this outlier, including dementia. Other folks showed IQ increases as they aged. In fact, on average, people's individual (or absolute) scores on the test taken again at age 80 was much higher (over 1 standard deviation) than their scores had been at age 11, even though the rank ordering among people stayed roughly the same.

Posted by Jim Zellmer at November 6, 2011 1:37 AM
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