The two roots

The seeds of a potential source of confusion have already been sown by the use of several different terms. We started by talking about intelligence, then we slipped into referring to IQ and had to note that it was a measure of intelligence. Finally we mentioned something called g, or the g-factor, and used it much as though it were just another name for intelligence. These terms are, most emphatically, not synonyms. They are often treated as if they were and therein lies much of the confused thinking which muddies the waters of current debates. The roots of this muddle lie, to a large extent, in the vagaries of history, and it is to history, therefore, that we turn to begin to unravel the tangled threads.

Two routes may be traced from the origins of intelligence testing to the present day and it is interesting that there appears to have been little constructive interaction between them in the early stages. The first, which gave rise to the term IQ, started with Alfred Binet around 1905 and reached its zenith with the appearance of Lewis Terman's, The Measurement of Intelligence published in 1916. The second strand has its roots in Charles Spearman's pioneering paper of 1904 on factor analysis. Binet reviewed Spearman's paper unfavourably in the following year and Spearman, for his part, was no more impressed with Binet's work.