Individual Differences In Fluid Intelligence Research Articles

Developmental and individual differences in fluid intelligence: Evidence against the unidimensional hypothesis

The Brinley plot and partial correlation methods are used to investigate conjointly the theories that increasing speed of processing is responsible for changes in mental age (MA) and that speed of processing gives rise to within‐age differences in fluid intelligence (IQ). A group of 107 children ranging in age from 4 to 9 years completed three reaction time (RT) tasks (spatial, verbal and selective attention). Children were grouped first by chronological age then by fluid IQ, and Brinley plots of RT and RT difference scores (argued to give a purer measure of cognitive speed) were produced for each grouping. Two Brinley methods were compared: fixing the intercept of the line of best fit at the origin, and allowing it to vary. These produced quite different functions with correspondingly different implications for the speed theory. It is argued that previous findings of developmental speed increases (as measured by Brinley slope) may be an artifact of the fixed‐intercept method. When intercept was allowed to vary, findings indicated that speed did not change developmentally. Furthermore, when absolute RT and RT difference score findings were compared, partial correlations indicated that RT was related primarily to age rather than MA or IQ, whereas RT difference scores were related directly to IQ, but not to age or MA. We argue that the results are best accommodated by the theory that speed underlies stable IQ differences but not increases in MA. Instead, we argue that MA change may be better accounted for by children's increasing attentional ability.

Processing Speed, Working Memory, and Fluid Intelligence: Evidence for a Developmental Cascade

Processing speed, working memory capacity, and fluid intelligence were assessed in a large sample (N = 214) of children, adolescents, and young adults (ages 7 to 19 years) Results of path analyses revealed that almost half of the age-related increase in fluid intelligence was mediated by developmental changes in processing speed and working memory and nearly three fourths of the improvement in working memory was mediated by developmental changes in processing speed Moreover, even when age-related differences in speed, working memory and fluid intelligence were statistically controlled, individual differences in speed had a direct effect on working memory capacity which, in turn was a direct determinant of individual differences in fluid intelligence

Novelty as “representational complexity”: A cognitive interpretation of Sternberg and Gastel (1989)

A major principle of intelligence research is the ubiquitous relationship between a task's working memory demands and its sensitivity to individual differences in fluid intelligence and/or g. Sternberg and Gastel (1989) have provided yet another example of this well-known principle. There is no need to invoke additional constructs such as “novelty”.

The relationship between working memory and intelligence: Regression and COSAN analyses

In this paper, we use data from an experiment on working memory to explore the utility of two statistical techniques in the study of sources of individual differences. These are regression analyses and covariance structure analysis (COSAN). In general, the results do not support the view that capacity limitations are the source of individual differences in fluid intelligence. Using regression analysis, some support is found for the hypothesis, but on closer inspection, coupled with the COSAN results, it cannot be sustained.