An Experimental Study of the Inheritance of Intelligence

TLDR

Controversy over the nature of intelligence remains despite advances in factor analysis, which has evolved from a single‑factor model to Spearman’s two‑factor theory and further to group and multiple‑factor approaches. The study found that primary mental abilities intercorrelate to form a second‑order factor akin to Spearman’s g, supporting the view that intelligence is largely genetically determined.

Abstract

Although the development of factor analysis has led, at least operationally, to more precise description of the field of human cognition, controversy as to the nature of intelligence has not ended, although there has been a marked narrowing of the differences between extremes of view. On the one hand, the monarcheal, or single factor idea, has been superseded by Spearman's two factor theory which has in turn been extended to the consideration of group factors. On the other hand, the multifactorial approach has been narrowed and refined by Thurstonian Multiple Factor Analysis. The primary Mental Abilities described by this method were found to be intercorrelated giving rise to a second order factor which Thurstone has suggested, may be not unlike Spearman's “g”. Despite this basic disagreement as to the nature of the variable under consideration, results obtained have led investigators to almost complete agreement that what they have measured as intelligence is largely genetically determined.