<P>
Harnad, S. (1999) Why I believe intelligence can be measured by IQ
tests, and how universities could make use of them.
<I>
Times Higher
Education Supplement. </I>Friday February 12 1999.
<P>
<CENTER>
<B>
Why I believe intelligence can be measured by IQ tests (and how
universities could make use of them)
</B>
<P>
Stevan Harnad
<br>
Department of Electronics and Computer Science
<br>
University of Southampton
<br>
Highfield, Southampton
<br>
SO17 1BJ UNITED KINGDOM
<br>
harnad@cogsci.soton.ac.uk
<br>
http://cogsci.soton.ac.uk/harnad
</CENTER>
<P>
This is not even a question of belief. It's an empirical question:
something that you can test and check. Psychometric tests are
deliberately constructed to correlate with certain things that people
can do in the real world, such as perceive and produce pitch and
rhythm in music, navigate in space, solve algebra problems, understand
complicated texts. Among other things, tests can be designed to predict
academic performance. The predictive power of such tests can be
validated by throwing out test-items that don't correlate and
constructing items that do until the test has a high enough correlation
with what it is trying to measure.
<P>
Those who question whether such tests are effective  usually haven't
given it a great deal of thought; they doubt IQ tests "in principle,"
usually for (noble) ideological reasons -- they prefer a world (as do
I) in which aptitudes are all identical and only individual effort
determines success in every field of endeavour -- or they doubt tests
on the basis of personal experience (invariably negative personal
experience) of how unfair and unrepresentative their own test results
have been. But those who know (not believe, know) that tests do work
base this on their predictive power at the population level, not from
indivividual experience. positive or negative. They have analysed the
scores of large numbers of people and confirmed the strong correlation
between the scores on those tests and how people actually perform in
the world. Tests will sometimes under- (or over-) predict: statistics
are like that; they are not infallible in every individual case. But if
they are robust, they should do a good job overall for the population
as a whole. The rest is down to what you want to use the results for.
If you want to select candidates who are likeliest to pass a demanding
course, you will want to be guided predictive tests. 
<P>
There are legitimate differences in judgment over the degree to which
aptitude tests measure a fixed inborn potential or the outcome of
experience and effort. Scores are probably a reflection of both; what
the relative proportions are is controversial, but by the time people
reach the age of, say, 16-17, their aptitudes, whether genetic or
experiential, have largely "solidified": they no longer change very
much (some say they never did). So a second controversial question, and
a much more practical one, is:  Once it's solidified like that, at a
population level, what is the best way to channel it?
<P>
I favour more people getting into university: The larger the proportion
of the population gaining a higher education, the more everyone gains,
individual and population. But to assume that everyone's aptitude is
identical is a mistake. If, in an effort to increase admissions,
universities keep their level of instruction fixed but lower their
entry requirements, there are only two possible outcomes; either a
larger proportion of the student population is going to fail out (which
defeats the purpose of admitting more) or content requirements must be
lowered to match the lower entrance requirements. But then the result
is more higher education degrees, but not necessarily more higher
education overall (which again defeats the purpose of the expansion).
<P>
There is another way, not an unfamiliar one, as it was applied in this
country (too early, at age 11, and too rigidly) in the form of
"streaming." Different curriculum levels (between or within
universities) would be designed to match differences in incoming
aptitude. Our tests are probably too crude for anything finer-grained
than a 3-4 tier system, with the middle 2nd and 3rd the biggest, in
keeping with the "bell" shape of all normal population distributions
(e.g., for height, most of us are near the average, high normal or low
normal, fewer are nearer the extremes).
<P>
The only alternative to having the universities conform to the incoming
curve ito deform the universities so they all regress on the population
average. I believe everyone loses in that case.