The David Gribble Archive : Talks

Children don’t start wars

Leipzig University, 2008
Page 2

This decline too starts when we are very much younger than most people realise. David Wechsler, the man who invented the Wechsler intelligence tests, did some interesting research in1939. (I know that intelligence tests are not a true measure of ability, but they do measure something.) Wechsler divided intelligence into a number of abilities which could be tested and measured – memory, comprehension, arithmetic, recognising similarities, etc. Here are his own words about his findings.

Every human capacity after attaining a maximum begins an immediate decline. This decline is at first very slow but after a while increases perceptibly. The age at which the maximum is attained varies from ability to ability but seldom occurs beyond 30 and in most cases somewhere in the early 20's. Once the decline begins it progresses continually. … Many of our intellectual abilities show a greater impairment with age than do our physical ones.

Hitherto the common view has been that our mental abilities, unlike our physical abilities, remain relatively unimpaired until rather late in life (senility), except as an occasional consequence of disease or traumatic injury. This was an unsubstantiated hypothesis tenable only so long as no facts were at hand to oppose it. But the view still persists even though such facts are now available. Most people, including scientists, hate to believe that they are not as mentally alert at 50 as they were at 20.

In this respect not much seems to have changed since 1939.

In his experiment Wechsler recorded the average scores for children in year-groups, and for adults in five-year groups. The oldest group he tested were between 55 and 59. These are the levels they reached in some of the tests, in comparison with children:

twelve-year-old level – information, comprehension, picture completion
eleven-year-old level – arithmetic, similarities, overall score
ten-year-old level – digit span, block design, object assembly
nine-year-old level – digit symbol, picture arrangement.

That was in 1939. I looked briefly on the internet for more up-to-date information, and could only find the following confirmation of Wechsler’s findings. In the 1990s the scores found by Joseph Maturazzo, using the WAIS test, the Wechsler Adult Intelligence Scale, were as follows:

Late teens: 110
Mid-twenties: 117
Mid-forties: 106
Seventies: around 70

This sort of decline has now also been confirmed by neurological research, which has also shown that the very youngest brains are in some respects superior to older ones. As Alison Gopnik, Andrew Meltzoff and Patricia Kuhl, wrote in their book, How Babies Think, published in 1999:

If you combine the psychological and neurological evidence, it is hard to avoid concluding that babies are just plain smarter than we are, at least if being smart means being able to learn something new.