Thorndike’s Credo: Metaphysics in psychometrics

Abstract

Endorsing a priori the conviction that any science worthy of the name must measure the attributes it investigates, psychometricians adopted a metaphysical paradigm (without acknowledging it as such) to secure its claim that mental tests measure psychological attributes, a claim that was threatened by the inadequacy of test data to secure it. The fundamental axiom of this paradigm was Thorndike’s Credo (“All that exists, exists in some amount and can be measured”; 1918, p. 16), which entails its central lemma, the psychometrician’s fallacy (“All ordered attributes are quantitative”; Michell, 2009, p. 41), and which, in turn, supplies psychometrics’ primary methodological principle (“interval scales can be derived from ordinal data”). Logically, this framework is flawed at every level: Thorndike’s Credo is metaphysical overreach; the psychometrician’s fallacy is just that—a logical fallacy; and their primary methodological principle, a prioristic thinking.

“The art of imposing measurement upon the mind”: Sir Francis Galton and the genesis of the psychometric paradigm

“… 38. Thorndike (1936), who belonged to a later generation of psychometricians, once admitted, “the writings of [William] James and Galton influenced me most” (p. 268) and he articulated the metaphysical underpinnings of Galton’s position (Michell, 2020b). …”

“… 65. I have traced various episodes in the history of psychometrics from this perspective (e.g., Michell, 1997, 2009a, 2012, 2013, 2020b, 2021). …”

“… 68. For a critical account of this misstep see my recent paper in this journal (Michell, 2020b). Kerlinger and Lee (2000) neatly expressed the dominant psychometric attitude: “Most behavioral and social science data are ordinal.…”

“Are psychological attributes quantitative?” is not an empirical question: Conceptual confusions in the measurement debate

“…Since concepts of psychological measurement discussed in this debate are inspired by measurement in natural sciences such as physics, answers to this question boil down to exploring whether psychological phenomena are quantitative just as physical attributes are. Two influential positions in this debate that are highly critical of quantitative psychology 1 are those put forward by Joel Michell (1997Michell ( , 2000Michell ( , 2003Michell ( , 2010Michell ( , 2011Michell ( , 2012Michell ( , 2020 and Günter Trendler (2009, 2019a, 2019b). Michell criticizes quantitative psychologists for assuming that psychological attributes are quantitative without attempting to test this hypothesis.…”

Taking the Humanities Seriously

“…I therefore confine my analysis to ways in which psychological scientists have been called upon to incorporate the arts and humanities in their research. Although ontological/metaphysical critiques of psychological science abound (e.g., Hibberd, 2014; Koch, 1981; Michell, 2020; Petocz & MacKay, 2010; Robinson, 2007; Sass, 1988; Stam, 2012; Teo, 2020), I focus especially on epistemic concerns, as those who have advocated psychology’s turn to the humanities have also tended to be critical of psychology’s traditional approaches to acquiring knowledge about mental life (e.g., Bishop, 2018; Churchill, 2012; Cushman, 2012; Lamiell, 2018, 2019; J. Martin, 2017; J.…”