Iris van Rooij

The tractability fallacy of bounded or ecological rationality

Fallacies are often explained by the fact that rational reasoning is beyond the computational powers of resource-bounded minds like our own. For instance, rationality defined in terms of axioms of logic or probability theory is provably intractable (e.g., NP-hard). Therefore, so the argument goes, humans must resort to short-cuts or heuristics, and fallacies are a natural consequence. Some researchers have objected to this bleak view of the mind and proposed that humans are rational after all, albeit in a ‘bounded’ or ‘ecological’ sense.  Here ‘bounded’ refers to the non-optimality of the reasoning, and ‘ecological’ to its presumed fit to the environment of adaptation. This proposal seems to be based on the belief that these alternative senses of rationality are tractable. In this talk, I will demonstrate why this belief is itself a fallacy. The upshot of this is not that humans aren’t rational or irrational in some sense. Rather, it shows that intractability is a more general challenge for accounts of rationality than previously thought. Moreover, the solution is not to be found in short-cuts per se, but requires a careful analysis of the conditions that make rationality tractable, be it classical, bounded, ecological or otherwise.