Peter H. Schonemann
Famous artefacts: Spearman's hypothesis. (Target Article).
Cahiers de Psychologie Cognitive/Current Psychology of Cognition, 1997, 16, 665-694.
In a number of publications, Jensen has recalled Spearman's (1927, p.379) observation that the loadings of the first principal component (PC1) of various 'intelligence tests' tend to correlate positively with the corresponding Black/White mean differences ('Spearman's Hypothesis').
Jensen believes this sheds light on the true nature of g, Level II Ability, test bias, and Black/White differences. His claims have been warmly welcomed in some quarters (most recently by Herrnstein and Murray, 1994) as conclusive confirmation of the Black inferiority myth.
Here it is shown by way of empirical, numerical, geometric, and algebraic demonstrations that the positive correlations predicted by Spearman's hypothesis are psychometric artefacts which also arrise
(a) with measures which have nothing to do with 'general ability', for example, the number of toys and books a child has; and, more generally
(b) with any set of moderately correlated random data, once the sample is split into high and low groups.
Specifically, this interpretation predicts that, if sample sizes differ substantially, then the correlation will be larger for the PC1 of the larger group. This prediction is borne out both in simulated and in 'real' data sets, including Jensen's.
Mostly nontechnical. The technical core is contained in Schonemann (1992).
This Target Article is essentially an expanded version of Schonemann (1989). It was followed by 12 Commentaries and a detailed Response, all in the same issue of CPC.
It took fully 12 years to put these results on record. For a fairly complete timeline of efforts to have them published in the American psychological and statistical literature, see Schonemann, P. H. (unpublished): Better never than late: Peer review and the preservation of prejudice.