Human intelligence

Whoops: long silence!  Look, I'm busy on Not Your Usual Science, so here's an excerpt from that.

We would all agree that humans are intelligent, but what is it, and how is it defined? One description says that intelligence is what is measured by intelligence tests — which is not really very helpful.

Intelligence is more usefully defined as the ability to respond adaptively to novel situations, but the standard IQ test is designed to measure the likelihood of success in learning and examinations, which has only a small overlap with responding adaptively. The IQ measure is useful in counselling and placement, but only when used in skilled hands. IQ is of little use in assessing true worth.

Most tests are based on an assumption that the mean score will be set at 100, with people’s scores distributed on a bell-shaped curve, allowing psychologists to assert that 2/3 of all people have a score between 84 and 116, and 95% of people will have scores between 68 and 132.

The original IQ tests were designed mainly to identify students who were of below average intelligence, to select students for placement in remedial education. While teachers could be asked to perform this selection, their judgements might be shaded by conscious and unconscious biases, so objective tests seemed like a good idea.

By giving these tests to large numbers of students at various ages, averages for each age group (“norms”) could be determined. The tests, even when the questions were simplistic, served (and still serve) a useful function. If a child is having difficulties in class, but at the same time, the tests indicate an above-average IQ, this normally indicates a problem which needs to be dealt with, mainly by counselling.

At their best, the various IQ tests have never shown themselves to be really effective predictors. A correlation of 0.5 between scholastic success and IQ is the normal expectation, indicating an overlap between what the two measures cover of no more than 25%.

The scores on alternative forms of the test (“parallel forms”) are controlled as tightly as possible, but the tests will always be unreliable to some extent. In particular, high and low scorers, when retested will, on average, score closer to the mean on the second attempt at the test, due to an effect called “regression to the mean”.

IQ test scores have been more abused than used wisely, and now their use is restricted. The tests have not failed, in their original purpose: rather, too many of the users of the test scores, especially untrained teachers, have failed to use the scores properly.

Much of the opposition to using IQ tests has come from teachers who have seen only the damage that the misuse of test scores can lead to. To this criticism, they add the valid complaint that there is more to intelligence than the ability to score well on IQ tests, that intelligence also includes creative thinking and divergent thinking. How, they ask, can an objective (multiple-choice) test allow for the child who suggests that the plural of “leaf” is “tree”?

Multiple intelligences

Teachers today are far more at home with a notion, first proposed by Howard Gardner, which breaks away from the usual narrow definition of intelligence, either as IQ, or as Spearman’s g (look it up!). At best, the old tests cover verbal and non-verbal IQs, but the school of thought founded by Gardner, and widely accepted by teachers around the world, expands into a wide range of other evidences of intelligence.

Gardner’s intelligences are not well-suited to measurement, but they are eminently useful as a way of planning instruction which allows all students to shine in their strong areas, and to develop their weak areas.

Musical intelligence is shown best in child musical prodigies. Gardner also cites examples such as autistic children who can play an instrument beautifully, but who cannot speak. (This also raises an interesting way of looking at one solution offered to people who stammer, who are often advised to sing the statement they wish to make.)

Bodily-kinesthetic intelligence is found in the natural sports player, or the talented dancer.

Logical-mathematical intelligence is largely the attribute measured by traditional IQ tests of non-verbal IQs, a skill which is clearly distinguished from verbal intelligence. The “idiot savant” who calculates brilliantly is an extreme case, a person who seems to have only this intelligence, and no other, although there are also remarkably “ordinary” people who have similar powers of calculation and reasoning.

Others, like Sir Isaac Newton, who are able to consider a falling apple, wonder why the Moon did not fall in the same way, and leap intuitively to the idea that gravity obeys an inverse square law.

Linguistic intelligence even has its own area of the brain, Broca’s area, which is responsible for assembling grammatical sentences. But while we all have the gift of language, some have it in much greater degree than others. Gardner points out that, at the age of ten, T. S. Eliot created eight issues of a magazine called ‘Fireside’ in three days, each featuring a wide variety of linguistic styles.

Spatial intelligence is important to the navigators of Polynesia and Micronesia, who have a feel for the oceans they travel. It can also be seen in the work of visual artists, and is probably important in sports such as tennis and squash. It may well be just as important to the better chess player, who “chunks” the relationships on a chess board at a glance, instantly perceiving the spatial relationships between the different pieces.

Interpersonal intelligence is all about being able to work with other people. As we will see later, Sir Isaac Newton clearly had a number of intelligences in vast supply, but he seems to have been limited when it came to interacting successfully with other people. A good politician, sales representative or teacher needs to have a good supply of this intelligence.

Intrapersonal intelligence involves the skill of knowing oneself. This is the most hidden intelligence, since it can only be demonstrated by the use of the language, music, or other more expressive forms of intelligence.

My own definition? I think intelligence is a construct, most useful as a weapon which can be used to skewer and damn those on the other political wing.