Item responses to Digit Span and Letter-Number Sequencing were analyzed to develop a better-refined model of the two working memory tasks using the finite mixture (FM) modeling method. Models with ordinal latent traits were found to better account for the independent sources of the variability in the tasks than those with continuous traits, and…

In a population-based sample of 112 nine-year old twin pairs, we investigated the association among total brain volume, gray matter and white matter volume, intelligence as assessed by the Raven IQ test, verbal comprehension, perceptual organization and perceptual speed as assessed by the Wechsler Intelligence Scale for Children-III. Phenotypic…

Although it is widely acknowledged that chess is the best example of an intellectual activity among games, evidence showing the association between any kind of intellectual ability and chess skill has been remarkably sparse. One of the reasons is that most of the studies investigated only one factor (e.g., intelligence), neglecting other factors…

A previous study on the underlying structure of the Wechsler intelligence test (WISC-R; [Wechsler, D. (1974). Manual WISC-R: Wechsler intelligence scale for children-Revised. New York: Psychological Corporation]), using smallest space analysis (SSA) [Guttman, L., and Levy, S. (1991). Two structural laws for intelligence tests.…

Two structural laws for intelligence tests are discussed: one law concerns the sign of correlation coefficients and gives conditions under which all correlations between test items will be positive; and one law concerns the relative sizes of the correlation coefficients between intelligence items. A cylindrical structure extends these laws. (SLD)

This study examined the phenotypic and genotypic relationship between working memory speed (WMS) and working memory capacity (WMC) in 12-year-old twins and their siblings (N = 409). To asses WMS all children performed a reaction time task with three memory loads from which a basic mental speed measure and the derived slope were used. WMC was…

Genetic and environmental correlations among 11 Wechsler Intelligence Scale for Children-Revised (WISC-R) subtests were estimated from a sample of 143 twin pairs using the methodology of multivariate behavioral genetics. Correlations due to within-pair environmental influences were generally small, whereas those due to shared environmental…

Reading deficits among elementary-aged learning disabled children with suspected neurocognitive dysfunctions were calculated. The children were grouped according to IQ profiles. Results indicated that the pattern of high verbal-low performance IQs was associated with the least deficiency in reading ; this association was evident as early as second…

Raw scores on WISC-R subtests and the verbal, performance, and full scale IQ scales were correlated with age separately for White and Black males and females. The relationship between age and intelligence test performance was constant across race and sex and supports the construct validity of the WISC-R. (Author/RD)

Interrelationships among IQ, academic achievement, and teacher ratings of pupils' classroom achievement were evaluated in a large sample of children from various racial and socioeconomic backgrounds. A substantial relationship between standardized measures of IQ and achievement was found and was independent of race, but decreased with increasing…