Longitudinal change in five cognitive abilities was investigated to determine if the direction or magnitude of change was related to the individual's ability level. Adults between 18 and 97 years of age performed three versions of 16 cognitive tests on two occasions separated by an average of 2.7 years. In order to control for influences…

The aim of the study was to investigate the relationship between the Flynn effect and the effects of age differences between siblings on the intelligence difference between them. In Norway, the secular trends in intelligence-test score means vary both in magnitude and direction. We identified three periods: one period where the mean intelligence…

Studies investigating evolutionary theories on the origins of national differences in intelligence have been criticized on the basis that both national cognitive ability measures and supposedly evolutionarily informative proxies (such as latitude and climate) are confounded with general developmental status. In this study 14 Y chromosomal…

There are very few studies on the relationship between cognitive ability and dental status in middle aged and younger adults. We postulate that lower cognitive ability is directly related to poorer dental status and that this relationship operates through the relationship between cognitive ability and health-related behaviors. The objectives of…

This register-based longitudinal study of 392 969 Norwegians examined associations between birth order, gender and educational attainment at age 25 years within families (fixed effects regression) and between families (ordinary OLS regression). Data were retrieved from national registers for births of mothers with single births only and a first…

Examined the regressions of occupational status and income on psychometric "g" factor scores in large samples of white (n=3,484) and black (n=493) U.S. armed forces veterans in their late 30s. Results indicate that, for both job status and income, whites were relatively more disadvantaged when the level of "g" is taken into…

This study investigated whether a unitary elemental process or several independent processes underlie psychometric "g" (factor of general intelligence). Results with 101 college students administered 2 intelligence tests and a large battery of elementary cognitive tasks suggest that as many as 4 independent components make up…

Because they used an inappropriate statistical procedure, J. H. Kranzler and A. R. Jensen (1991) have not demonstrated that a factor of general intelligence ("g") depends on several independent factors. A factorial reanalysis of their data suggests that speed and efficiency of information processing are important in "g." (SLD)

The hypothetical idea of a perfectly pure psychometric "g" is empirically unattainable. Because the unity of "g" cannot be proved or disproved by factor analysis, the unitary "g" hypothesis represents a parsimonious assumption. J. B. Carroll's (1991) analysis demonstrates the relationship between psychometric and…

In their reply to the present author's critique (1991), J. H. Kranzler and A. R. Jensen have still not demonstrated that a factor of general intelligence, "g," depends on, or contains, several independent factors. They have only demonstrated that an estimate of "g" is predictable from several independent components. (SLD)

Longstreth's critique of Jensen's research on the relationship of IQ to individual differences in visual reaction time (RT), measured in the Hick paradigm, is said to have numerous errors of fact and interpretation, some trivial and some of theoretical importance. (Author/LMO)

Etiology of high and low cognitive ability in adulthood was explored through multiple regression analysis of data from 302 pairs of Swedish twins (median age=65.6 years). Both high and low cognitive ability groups demonstrate significant group heritability, with shared rearing environment of relatively low importance. (SLD)

Two experiments with 172 undergraduate students (70 males and 102 females) examined the relationship among spatial, imagery, and verbal ability and the multitrial free recall of brief prose passages. Results suggest that the psychological mechanisms underlying prose learning performance clearly differ depending on the ability being examined. (SLD)