Journal of Intelligence and ISIR - pre-pub "in press" feature

For those serious about staying current with contemporary intelligence research, the journal Intelligence is a must subscription. I would urge blog readers to visit the ISIR (International Society for Intelligence Research) web page to consider joining this organization. Membership provides members with a subscription to the journal (members can also download pdf copies of the articles from the web site).

Another nice feature is that "corrected proof" pdf copies of "in press" articles are made available with regularity. This feature allows members to keep abreast of contemporary developments ASAP. I think this feature is a model that should be followed by other journals.

Below is a select number of abstracts from recently published "in press-corrected proofs" that were available for download.


Ashton, M. C., & Lee, K. (2005). Problems with the method of correlated vectors. Intelligence, In Press, Corrected Proof.

• The method of correlated vectors has been used widely to identify variables that are associated with general intelligence (g). Briefly, this method involves finding the correlation between the vector of intelligence subtests' g-loadings and the vector of those subtests' correlations with the variable in question. We describe two major problems with this method: first, associations of a variable with non-g sources of variance can produce a vector correlation of zero even when the variable is strongly associated with g; second, the g-loadings of subtests are highly sensitive to the nature of the other subtests in a battery, and a biased sample of subtests can cause a spurious correlation between the vectors.

Arendasy, M., & Sommer, M. (2005). The effect of different types of perceptual manipulations on the dimensionality of automatically generated figural matrices. Intelligence, In Press, Corrected Proof.

• Two pilot studies (n1 = 155, n2 = 451) are presented in this article, which were carried out within the development of an item generator for the automatic generation of figural matrices items. The focus of the presented studies was to compare two types of item designs with regard to the effect of variations of the property "perceptual organization" on the psychometric properties and concurrent validity of figural matrices. The main results not only indicate a comparably high concurrent validity of the automatically generated figural matrices with regard to Raven matrices but also point to interesting differential effects of two kinds of implementations of perceptual organization. The conclusion of the two studies is that a more thorough understanding of the component processes of inductive reasoning and especially the impact of various item features on their difficulty and psychometric properties must be obtained.

Barber, N. (2005). Educational and ecological correlates of IQ: A cross-national investigation. Intelligence, In Press, Corrected Proof.

• The new paradigm of evolutionary social science suggests that humans adjust rapidly to changing economic conditions, including cognitive changes in response to the economic significance of education. This research tested the predictions that cross-national differences in IQ scores would be positively correlated with education and negatively correlated with an agricultural way of life. Regression analysis found that much of the variance in IQ scores of 81 countries (derived from [Lynn, R., & Vanhanen, T. (2002). IQ and the wealth of nations. Westport, CT: Praeger]) was explained by enrollment in secondary education, illiteracy rates, and by the proportion of agricultural workers. Cross-national IQ scores were also related to low birth weights. These effects remained with national wealth, infant mortality, and geographic continent controlled (exception secondary education) and were largely due to variation within continents. Cross-national differences in IQ scores thus suggest that increasing cognitive demands in developed countries promote an adaptive increase in cognitive ability.

Johnson, W., & Bouchard, Jr. T. J. (. The structure of human intelligence: It is verbal, perceptual, and image rotation (VPR), not fluid and crystallized. Intelligence, In Press, Corrected Proof.

• In a heterogeneous sample of 436 adult individuals who completed 42 mental ability tests, we evaluated the relative statistical performance of three major psychometric models of human intelligence--the Cattell-Horn fluid-crystallized model, Vernon's verbal-perceptual model, and Carroll's three-strata model. The verbal-perceptual model fit significantly better than the other two. We improved it by adding memory and higher-order image rotation factors. The results provide evidence for a four-stratum model with a g factor and three third-stratum factors. The model is consistent with the idea of coordination of function across brain regions and with the known importance of brain laterality in intellectual performance. We argue that this model is theoretically superior to the fluid-crystallized model and highlight the importance of image rotation in human intellectual function.

Johnson, W., & Bouchard, Jr. T. J. (2005). Constructive replication of the visual-perceptual-image rotation model in Thurstone's (1941) battery of 60 tests of mental ability. Intelligence, In Press, Corrected Proof.

• We recently evaluated the relative statistical performance of the Cattell-Horn fluid-crystallized model and the Vernon verbal-perceptual model of the structure of human intelligence in a sample of 436 adults heterogeneous for age, place of origin, and educational background who completed 42 separate tests of mental ability from three test batteries. We concluded that the Vernon model's performance was substantively superior but could be significantly improved. In so doing, we proposed a four-stratum model with a g factor at the top of the hierarchy and three factors at the third stratum. We termed this the Verbal-Perceptual-Image Rotation (VPR) model. In this study, we constructively replicated the model comparisons and development of the VPR model using the data matrix published by Thurstone and Thurstone (1941) [Thurstone, L. L., & Thurstone T. G. (1941). Factorial studies of intelligence. Chicago: University of Chicago Press]. The data matrix was generated by scores of 710 Chicago eighth graders on 60 tests of mental ability.

Kempel, P., Gohlke, B., Klempau, J., Zinsberger, P., Reuter, M., & Hennig, J. (2005). Second-to-fourth digit length, testosterone and spatial ability. Intelligence, In Press, Corrected Proof.

• Based on stimulating findings suggesting that prenatal levels of steroids may influence cognitive functions, a study with N=40 healthy volunteers of both sexes was conducted. Prenatal levels of testosterone (T) were estimated by use of the second-to-fourth digit ratio (2D:4D) which is supposed to be controlled by the same genes involved in maturation of gonadal tissue and therefore may reflect the level of prenatal T. Moreover, activational effects of T were investigated by measuring T levels in saliva directly. Subjects completed several subtests of intelligence batteries for verbal, numerical and spatial abilities. Levels of T were not related to any of the cognitive functions. The 2D:4D was lower in males as compared to females. Males outperform females on spatial ability. Moreover, females with low 2D:4D performed better on cognitive tests measuring spatial as well as numerical ability as compared to females with high 2D:4D. Results are discussed with respect to the assumed role of prenatal and present levels of T in brain development and cognitive functioning.

Luo, D., Thompson, L. A., & Detterman, D. K. (2005). The criterion validity of tasks of basic cognitive processes. Intelligence, In Press, Corrected Proof.

• The present study evaluated the criterion validity of the aggregated tasks of basic cognitive processes (TBCP). In age groups from 6 to 19 of the Woodcock-Johnson III Cognitive Abilities and Achievement Tests normative sample, the aggregated TBCP, i.e., the processing speed and working memory clusters, correlate with measures of scholastic achievement as strongly as the conventional indexes of crystallized intelligence and fluid intelligence. These basic processing aggregates also mediate almost exhaustively the correlations between measures of fluid intelligence and achievement, and appear to explain substantially more of the achievement measures than the fluid ability index. The results from the Western Reserve Twin Project sample using TBCP with more rigorous experimental paradigms were similar, suggesting that it may be practically feasible to adopt TBCP with experimental paradigms into the psychometric testing tradition. Results based on the latent factors in structural equation models largely confirmed the findings based on the observed aggregates and composites.

McDaniel, M. A. (2005). Big-brained people are smarter: A meta-analysis of the relationship between in vivo brain volume and intelligence. Intelligence, In Press, Corrected Proof.

• The relationship between brain volume and intelligence has been a topic of a scientific debate since at least the 1830s. To address the debate, a meta-analysis of the relationship between in vivo brain volume and intelligence was conducted. Based on 37 samples across 1530 people, the population correlation was estimated at 0.33. The correlation is higher for females than males. It is also higher for adults than children. For all age and sex groups, it is clear that brain volume is positively correlated with intelligence.

Reed, T. E., Vernon, P. A., & Johnson, A. M. (2005). Confirmation of correlation between brain nerve conduction velocity and intelligence level in normal adults. Intelligence, In Press, Corrected Proof.

• In 1992, Reed and Jensen [Intelligence 16 (1992) 259-272] reported a positive correlation (.26; p=.002; .37 after correcting for restricted intelligence range) between a brain nerve conduction velocity (NCV) and intelligence level in 147 normal male students. In the first follow-up of their study, we report on a study using similar NCV methodologies, but testing both male and female students and using more extensive measures of cognitive abilities. One-hundred eighty-six males and 201 females, aged 18-25 years, were tested in three different NCV conditions and with nine cognitive tests, including Raven Progressive Matrices as used by Reed and Jensen. None of the 27 independent correlations in either the males or in the females are significant at Bonferroni-corrected probability levels, but 25 of 27 correlations in males and 20 of 27 correlations in females have positive signs. The exact binomial probabilities for these results are 5.6X10-6 and .002, respectively. We discuss possible reasons for the differences between the results of Reed and Jensen and our results. We also find that males have four percent faster NCVs than females with each of the three test conditions, probably due to their faster increase of white matter in the brain during adolescence.