“Professor Spearman has drawn over-hasty conclusions”: Unravelling psychometrics’ “Copernican Revolution”

Abstract

The significance of the dispute between Charles Spearman and Godfrey Thomson over the role of factor analysis in providing unambiguous evidence for Spearman’s two-factor theory has not been recognised for the crucial moment it actually was in the history of psychometrics. Thomson sketched an alternative to Spearman’s theory demonstrating that, factor analysis notwithstanding, there was no need to hypothesise that abilities are quantitative attributes. Spearman was blind to this fact and his stature within the discipline ensured that Thomson’s alternative was subsequently neglected. I argue that Spearman’s blindness was conditioned by his fealty to two idols of the age: the quantitative imperative and the psychometricians’ fallacy, both of which were secured in Spearman’s mind by his failure to fully understand the concept of measurement. Given his influence, Spearman’s blindness to the significance of Thomson’s critique was a cause of psychometrics’ relentless progress to becoming a pathological science.

Should psychology follow the methods and principles of the natural sciences? Introduction to the debate

“…Recently, Michell (2023) drew attention to the extremely strong quantitative imperatives that motivated key founding figures of psychology, with Galton's (1879) entrenched position being particularly noteworthy: "until the phenomena of any branch of knowledge have been subjected to measurement and number, it cannot assume the status and dignity of a science" (p. 149). Whether one agrees or disagrees with this perspective, we hope that this debate issue forms a starting point for further informed discussions on the relationships between psychology and other scholarly disciplines, including the natural sciences.…”

Analyzing discourse for implicit ontologies.

“…That is, when psychologists postulate an intrapsychic property (say, self-esteem, or an attitude), statistical treatment of response items from a questionnaire is often taken implicitly to deal with measurements of actual properties existing within the person (O'Doherty & Winston, 2014). Michell (2023) has recently shown how this conflation of a statistical construct with an actual property in the world (or within the subjective world of persons) also lies at the foundation of the development and ongoing application of factor analysis in psychology. In the absence of pointed discussions of the ontology of psychological variables, this slippage is rendered invisible.…”