The sustained attention of 16 mildly retarded and 16 nonretarded adults was assessed during 2 60-minute vigilance tests differing in memory demand. Performance of retarded subjects declined more rapidly in later stages than did that of the nonretarded subjects. Implications for the study of memory load are discussed. (SLD)

Sources of continuity among nine measures of infant cognitive processing and later childhood intelligence quotient were examined through developmental structural equation models applied to a sample of 208 twin pairs measured from 7 to 36 months. Skills assessed appear related to general cognitive ability in a relatively unstable manner. (SLD)

Two studies with 658 white and 353 African-American elementary school children performing reaction time tasks are offered in support of Spearman's hypothesis about the relative size of the mean African-American-white differences on mental tests as a function of the tests' loadings on psychometric "g." (SLD)

The effects of early educational intervention on the attainment of the Piagetian cognitive stage of concrete operations by 86 socioeconomically disadvantaged children aged 5, 6, and 7 years were assessed. The Concept Assessment Kit-Conservation developed by M. L. Goldschmid and P. M. Bentler (1968) was used. (SLD)

Two studies (N=4,261 persons) illustrate an inverse relationship between ability level and correlations among IQ measures. Low IQ subjects showed higher correlations than did high IQ subjects. Intercorrelations of IQ subtests, intercorrelations of cognitive ability measures, and correlations of IQ with measures of cognitive ability displayed the…