Which of the following concepts is central to the work of Spearman and Thurstone in psychometrics?

The concept of factor analysis is pivotal to the work of both Spearman and Thurstone in psychometrics because it provides the statistical methods necessary to identify and analyze the underlying variables that explain the patterns of correlations among different measures of cognitive ability.

Spearman introduced the idea of a general intelligence factor, 'g', which he derived through factor analysis, asserting that this single factor could account for the correlations seen between various cognitive tasks. Thurstone, on the other hand, challenged Spearman’s singular factor model by using factor analysis to argue for multiple primary mental abilities rather than a single intelligence factor.

Through factor analysis, both researchers significantly advanced the understanding of intelligence by allowing for a more nuanced exploration of the cognitive abilities that contribute to overall intelligence, whether that exists as a singular entity or as a collection of distinct but related abilities. This method laid the groundwork for subsequent theories and models of intelligence in psychology.