“…The role of individual differences and response variations in conditioning models has long been of concern (Hayes, 1953;Merrill, 1931;Sidman, 1952, for initial publications;Blanco and Moris, 2018;Calcagni et al, 2020;Gallistel, 2012;Gallistel, Fairhurst, and Balsam, 2004;Glautier, 2013;Jaksic et al, 2018;Mazur and Hastie, 1978;Smith and Little, 2018;Young, 2018, for recent ones). These differences have provoked a range of attitudes as diverse as discarding them as statistical errors around a clean theoretical learning curve, or taking them as proof that theoretical models are mere artifacts.…”