Examines the secular decline in Japan of the strength of Spearman's g, which is measured by the value of the intercorrelations of the subtests of the Wechsler Intelligence Scale for Children-R (WISC-R) and the Wechsler Adult Intelligence Scale (WAIS-R) among low-intelligence groups. Occurrence of a similar decline in France; Strength of Spearman's g as partly a function of common environmental factors.