What are the standards of practical rationality for laypeople? An experimental inquiry

Is it rational “to prefer even my own acknowledge'd lesser good to my greater” or “to prefer the destruction of the whole world to the scratching of my finger” (Hume, Treatise II.3.iii/1987, 416)? How we answer these questions depends on what we mean by rationality: Is it restricted to means-ends rationality or does it also involve prudence or morality? In this paper, we use experiments to determine the extent to which the folk conception of rationality aligns with the standards just mentioned. In our experiments, participants rank how similar the standards are to rationality, and evaluate decisions, in which the standards conflict with each other. We find that lay people judge instrumental rationality to be most similar to rationality in a general evaluation. However, concrete decisions that comply with moral standards are considered to be more rational than those that prioritize prudence or the agent’s given goals. The fact that different types of experiments yield different results on the association between rationality and the three normative standards hints at a central feature of folk thinking about rationality: When lay people consider what is rational, it is crucial which type of object is evaluated regarding rationality.