Psychologist and mathematician Ramond Cattell ushered into clinical psychology a number of novel concepts and terms. He brought into wide use the terms "factor analysis," "multivariate approach," and "fundamental factors." These terms are associated specifically with his structure-based systems theory of personality development.
Factor analysis is a statistical approach that seeks to identify correlations between two or more variables. Factor analysis requires researchers to first codify and categorize the human behaviors they study. This method is a radical departure from Freudian-style verbal analysis, in which the researcher relies heavily on his or her intuition in order to identify behavioral correlations or patterns.
Cattell's multivariate approach also made him unique among his peers. Rather than isolate his studies to one factor, i.e. personality, he took an integrative approach. Cattell's theory is among the earliest attempts to understand, in a comprehensive manner, all the various influences on human behavior.
Cattell identified 16 fundamental factors of personality in his model. He argued that these factors were the basic driving mechanisms of all other personality traits. Today, there is no consensus concerning the validity of the concept of fundamental factors. Nonetheless, the idea continues to shape academic discourse and has opened new possibilities for clinical research and practice.