ABSTRACT
Searching for cognitive elements of human mental ability differences, and focusing that search on g, has a venerable record in our field of inquiry. The search, which Hunt (1980) compared with the search for the Holy Grail, is an interesting one to document, partly because researchers’ opinions on the same data can be diametrically opposed. In 1904 Spearman found small to medium-sized correlations between mental ability estimates and measures of sensory discrimination. He speculated that, after correcting for unreliability in the measures, the correlation between discrimination and mental ability was near to 1.0, and that discrimination was the psychological basis of human mental ability differences. (Although he withdrew the comment a few years later [Burt, 1909-1910], he repeated it in his magnum opus [Spearman, 1927]). In 1909 Thorndike, Lay, and Dean found very similar correlations to those of Spearman when they examined sensory discrimination and higher level mental abilities, and they remarked that it was tenable to conclude that discrimination and mental ability differences were unrelated (a correlation=0.0). Such is the violence that prior theory may wreak on congruent data.
