A long ‘intellectual’ journey

Matriculating in the quantitative/measurement psychology program at the University of Illinois provided numerous opportunities to develop the author quantitative skills and to explore different contexts for the study of individual differences in intellectual abilities. Although broad content abilities had been well studied in the literature since early in modern psychology and were dominant in Thurstone’s Primary Mental Ability framework, perceptual speed and psychomotor abilities had been relatively neglected in both research and application since around the 1950s. Most critically, crystallized intellectual abilities represent something that is less reactive to high-stakes testing, because it is acquired over long periods of education and experience. Initial research based on assessment of the depth and breadth of domain knowledge in samples of participants ranging from 18-year-olds to 70-year-olds provided a wealth of information about the nature of crystallized intellectual abilities and established several important findings.