The differentiation hypothesis suggests that the degree to which general intelligence ("g") pervades performance on mental tests is greater at lower ability levels. Analysis of data from Differential Aptitude Test results for over 10,500 Irish school children ages 14 to 17 years supports the differentiation hypothesis. (SLD)

This article examines the potential contribution of latent trait models to the study of intelligence. Nontechnical introductions to both unidimensional and multidimensional latent trait models are given. Multidimensional latent trait models can be used to test alternative multiple component theories of test item processing. (Author/CTM)

Meta-analysis of 225 hypothesis tests of measures of memory for order (MFO) and the relationship of MFO and measures of general ability demonstrate a significant relationship between MFO and standardized test scores. Fifty-one independent samples were tested. MFO task quality was a significant predictor of effect size. (SLD)

The general intelligence factor (g) was investigated using 170 university students across three batteries of ability measures: (1) a short-term memory battery; (2) the Multidimensional Aptitude Battery; and (3) a reaction time battery. Results support the notion of g and suggest short-term memory as an essential aspect of intelligence. (SLD)

A comparison was made of ability and achievement test results and school grades for 323 pairs of Swedish male and female twins and 740 controls in relation to social background. An interaction effect of sex and social background was found for verbal ability and mathematics test results. (SLD)