Does IQ Measure Intelligence?

Abstract

This question is often asked, but it is probably an inadmissible and meaningless question. Does the thermometer measure temperature? If by “temperature” we mean the scientific concept, embodied in a series of laws, then by definition the answer is “Yes”; temperature is almost defined as that which is measured by a thermometer. Similarly if by “intelligence” we mean the concept as worked out by psychologists along the lines indicated in the last three chapters, then obviously IQ tests, properly constructed, measure intelligence; indeed, in a very real sense intelligence may be defined as that which is measured by IQ tests provided we allow for the presence of chance error, which is attached to all scientific measurement, and provided that the rules of test construction are followed which we have already discussed. But both temperature and intelligence arose as concepts from common, everyday observation - of hot and cold sensations in the one case, of bright and dull people, in the other. Do scientific measurements agree with commonsense observations? This question is not of very great interest if put like this, for several reasons. Nevertheless, the search for “external validity”, i. e. for agreement between scientific measurement and criteria external to that measurement, which are agreed to be relevant to the concept in question, is of some importance, and certainly of social relevance in the case of intelligence testing; it will therefore be discussed in this chapter.

If you wish to strive for peace of soul and pleasure, then believe; if you wish to be a devotee of truth, then inquire. Nietzsche