...believe that intelligence can be measured by IQ tests and think universities could make use of them

This is not even a question of belief. It is an empirical question: something that you can test and check. IQ tests are deliberately constructed to correlate with things that people can do, such as perceive rhythm in music and understand complicated texts.

IQ tests can be designed to predict academic performance. The predictive power of such tests can be validated by throwing out test items that do not correlate and constructing items that do until the test has a high enough correlation with what it is trying to measure.

Those who question whether such tests are effective usually have not given it a great deal of thought; they doubt IQ tests "in principle", usually for ideological reasons, or they doubt tests on the basis of personal experience of how unfair their own test results have been.

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But those who know that IQ tests work base this on their predictive power at the population level, not on individual experience. They have analysed the scores of large numbers of people and confirmed the strong correlation between these scores and how people actually perform in the world. The rest is down to what you want to use the results for.

There are legitimate differences in judgement over the degree to which IQ tests measure a fixed inborn potential or the outcome of experience and effort. Scores probably reflect both; what the relative proportions are is controversial, but by the time people reach the age of, say, 16 or 17, their aptitudes, whether genetic or experiential, have largely "solidified": they no longer change very much.

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So a second controversial question is: once IQ is solidified like that, at a population level, what is the best way to channel it?

I favour more people getting into university. But to assume that everyone's aptitude is identical is a mistake. If, in an effort to increase admissions, universities keep their level of teaching fixed but lower their entry requirements, there are only two possible outcomes; either relatively more students are going to fail (defeating the purpose of admitting more) or the content of degrees must be lowered to match the lower entrance requirements.

There is another way, not an unfamiliar one, as it was applied in this country (too early, at age 11, and too rigidly). Students could be "streamed", grouped into different curriculum levels (between or within universities), depending on their performance in IQ tests. Our tests are probably too crude for anything finer-grained than a three to four-tier system, with the middle tiers the biggest, in keeping with the "bell" shape of all normal population distributions.

The only alternative to having the universities conform to the incoming curve is to deform the universities. I believe everyone loses in that case.

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Stevan Harnad

Professor of cognitive science at the University of Southampton. This week he hosts an open lecture at Southampton by behavioural geneticist Arthur R. Jensen