Factor analysis
Cattell noted that in the hard sciences such as chemistry, physics, astronomy, as well as in medical science, unsubstantiated theories were historically widespread until new instruments were developed to improve scientific observation and measurement. In the 1920s, Cattell worked with Charles Spearman who was developing the new statistical technique of factor analysis in his effort to understand the basic dimensions and structure of human abilities. Factor analysis became a powerful tool to help uncover the basic dimensions underlying a confusing array of surface variables within a particular domain.