Correlations of mental tests with each other and with cognitive variables are highest for low IQ groups

Abstract

Two studies showed an inverse relationship between ability level and correlations among IQ measures. Low IQ subjects showed much higher correlations than high IQ subjects. Intercorrelations of IQ subtests, correlations of cognitive ability measures with each other, and correlations of IQ with measures of cognitive abilities all displayed the same effect. In the first study, data from two experiments in which subjects took a battery of basic cognitive tasks and a standard IQ test were analyzed. Measures from the basic tasks correlated more highly in the low IQ group than in the high IQ group. In the second study, data from the WAIS-R and WISC-R standardization samples were divided into five ability groups. Average correlations among subtests were computed for each ability group. For both the WAIS-R and WISC-R, average subtest correlations were highest in the low ability group. Correlations declined systematically with increasing IQ. In both studies, correlations were found to be two times higher in low IQ groups than in high IQ groups.