History
Louis Leon Thurstone hailed from Chicago, Illinois. He was born on May 29th, 1887, and passed away on September 30th, 1955. He was the founder of psychophysics and psychometrics studies. He authored many works including intelligence testing theories, the law of comparative testing among others (Thurstone, 1938).
Definition of factor analysis
Factor analysis is one of the statistical methods used to explain the unpredictability of observed variables based on a fewer unobserved variable called factors (Thurstone, 1938). It helps to analyze and estimation of how much variability is suitable to common factors. This approach is used in psychology and mostly in intelligence research although it is also used in the analysis of personality, attitudes among other studies (Thurstone and Thurstone 1941).
Thurstone’s Multi-factor analysis of intelligence
Louis Thurstone in 1935 published his book in factor analysis called Multiple-Factor Analysis which took factor analysis study to the next level. It is not easy to calculate the multiple factors from a set of observations on a group of people. Multiple factors in the study of intelligence are not something that psychologists could readily do during the times of Thurstone as they lacked sophisticated technologies like the use of computers and other statistical methods. Due to the resemblance of multi factors used by Thurston, he called them the vectors of mind because of their relationship with the eigenvector. In his works on multiple factor analysis of intelligence, he believed that human intelligence is multifaceted since one can be of average intelligence but can be highly talented in other fields like football, music, or even mathematics, and so on(Thurstone, 1938). Using this observation he came up with Primary Mental Intelligence (PMAs) theory which was based on human intelligence. This theory stated that each person posses different intelligent factors and at different levels. He disagreed with the then-popular Charles spearman’s singular general intelligence theory which featured much in psychometric tests. Charles’s theory argued that regardless of the domain and how it was tested, all mental tests tend to load on one major factor and thus these scores are fuelled by a pool of mental energy which is called g. Thurstone argued that g was a statistical artifact resulting from the mathematical procedures used to study it (Thurstone and Thurstone 1941).
Foundations of intelligence behavior
According to Thurstone, a general factor can not be the origin of intelligent behavior. The source of intelligent behavior comes from the seven independent factors that he termed primary abilities. This includes the fluency of words, verbal command, spatial idea, number facility, associative recollection, way of thinking, and the speed of perception speed (Thurstone, 1938). From the mental data that was collected of different people, Thurstone came to realize that although people have similar overall IQ scores, they have different primary mental abilities and thus supporting his work over that of Charles since his work contained many clinical utilities than that of Charles’s unitary theory. When Thurstone tried to test his theory on children, the seven primary abilities were separate but the evidence of g was very present. Due to these contradictions, Thurstone managed to formulate a mathematical solution which was a compilation of both general factors and seven primary abilities which became the basis of future research on topics related to hierarchical theories and multiple intelligence theories (Thurstone and Thurstone 1941).
Conclusion
Thurstone suggests that the evolution of human intelligence occurs in seven-dimensional liberty. This is left to scholars to decide if there is the existence of 7-dimensional intelligence or it is just a mathematical construct.
References
Thurstone, L. L. (1938). Primary mental abilities. Chicago: University of Chicago Press.
Thurstone, L. L., & Thurstone, T. G. (1941). Factorial studies of intelligence. Chicago: University of Chicago Press.