Which researcher contributed to psychometrics by helping develop factor analysis?

The researcher who contributed significantly to psychometrics through the development of factor analysis is Spearman. He introduced the concept of factor analysis as a statistical method to identify underlying relationships between observed variables, which is fundamental in assessing intelligence and other psychological traits. Spearman's work laid the groundwork for measuring general intelligence (g factor) and demonstrated how different cognitive abilities are interrelated. This method allows researchers to understand the latent constructs that explain the correlations among various test scores, making it a pivotal development in psychometric theory.

While other researchers mentioned in the question have made important contributions to psychology and intelligence testing, none have had as direct an influence on the establishment of factor analysis as Spearman.