 Paul Meehl’s review in the 1950s of psychological studies using statistical methods versus clinical judgment cemented the statistical turn in psychology (Meehl 1954). Meehl’s review found that studies involving the prediction of a numerical target variable from numerical predictors is better done by a proper linear model than by the intuitive judgment of clinicians. Concurrently, the psychologist Kenneth Hammond formulated Brunswik’s lens model  (section 3.2)  as a composition of proper linear models to model the differences between clinical versus statistical predictions (K. Hammond 1955). Proper linear models have since become a workhorse in cognitive psychology in areas that include decision analysis (Keeney &amp; Raiffa 1976; Kaufmann &amp; Wittmann 2016), causal inference (Waldmann, Holyoak, &amp; Fratianne 1995; Spirtes 2010), and response-times to choice (Brown &amp; Heathcote 2008; Turner, Rodriguez, et al. 2016).