On Simpson’s paradox: To remain or not to remain a population-based science

Abstract

In this article, I critically reflect on J. F. Arocha’s (2021) contention that psychologists need to use methods and tools that are suitable for data analysis at the individual level. First, I discuss the beleaguered nature of the philosophical underpinnings of the standard practices in psychological research. Of the five assumptions he presented, the aggregate assumption results in Simpson’s paradox, a form of ecological fallacy. While the other assumptions need urgent attention, the proposals Arocha makes for addressing the aggregate assumption are still unsettled in many ways. I show that while perceptual control theory informed by the Aristotelian concept of final cause or telos allows for embracing variability as a psychological fact of human behaviour, one cannot say the same for his recommendation for the use of observation-oriented modelling (OOM) to address the aggregate assumption or to circumvent Simpson’s paradox.