Data from a previous adoption study using the Wechsler Intelligence Scale for Children-Revised show that the genetic effect is reflected by psychometric "g" (general intelligence) to a greater degree than is the environmental effect. This finding is consistent with the hypothesis that "g" largely reflects the genetic component…

Taylor (1980) claims to show that the similarity in IQ between monozygotic twins reared apart found in prior studies is due to similarity in their environments. A reanalysis using Taylor's classification of environments but an alternative IQ measure shows that his findings do not constructively replicate. (Author/RD)

The genetic relationship between intelligence and components of cognition remains controversial. Conflicting results may be a function of the limited number of methods used in experimental evaluation. The current study is the first to use CANTAB (The Cambridge Neuropsychological Test Automated Battery). This is a battery of validated computerised…

A battery of "g" loaded mental ability tests was administered to 274 Bedouin children and adolescents, full and half siblings from 106 families. Results demonstrate internal validity for the tests in this cultural context and support the idea that shared family environment is a strong determinant of sibling similarity for children in the…

It is argued that the statements and accusations made by Stephen Jay Gould about the use of factor analysis are incorrect and unjustified and that tests properly designed for the purpose can adequately measure a "general" or "g" factor of intelligence, particularly in view of the developments in testing since "The…

IQ tests and intelligence were discussed from an evolutionary perspective and implications concerning legal decisions and social policy were presented. It was concluded that disproportionate social and economic benefits need not result from the use of IQ tests in the selection of educational and occupational elites. (RD)

The construct of general intelligence is discussed in the context of factor models, differential validity of tests, Piagetian tasks, heritability, social class, and race. The general factor is an abstraction resulting from genes, environmental pressures, and neural structures involved in cognitive or intellectual human behavior. (Author/RD)

R. Herrnstein and C. Murray, in "The Bell Curve," stated six propositions concerning a "g" factor of intelligence. These propositions are found to be reasonably well supported in the scientific literature. These conclusions can be reached whether or not one accepts Herrnstein and Murray's claims about the social significance of…

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…

The Ramey and Haskins intervention experiment is examined. Narrow transfer of training from cognitive intervention techniques to IQ test performance in early childhood, rather than enhancement of the g factor itself, is hypothesized as a cause of the typical fadeout of early IQ gains in later childhood. (Author/RD)

Disparities between European countries and the U.S. in terms of incidence and prevalence of mild mental retardation have become apparent. A model of intellectual performance that might explain disparities and predict future levels of occurrence of mild mental retardation is presented. Such explanations are relevant for theory and policy decisions.…

Ramey and Haskins report two findings of major importance: absence of decline in test scores and absence of mother-child correlation for treated children. Implications of these findings are discussed. (Author)

Results from the Colorado Adoption Project, a longitudinal study initiated in 1975, are reported. The cognitive ability of parents and measures of one-year olds' mental development were significantly correlated for all three parent/child comparisons. Caldwell's HOME Responsibility measure was correlated with infant intelligence in adoptive and…

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)

Separate dimensions of infant cognition were compared with parental general- and specific-cognitive abilities for 182 adoptive and 164 nonadoptive families. More parent-offspring resemblance was present when 24- rather than 12-month Bayley factors were used. Bayley factors were more related to parental g than to specific abilities. (Author/RD)