We are studying rational choice… IN WORMS! Rationality for economists means making optimal decisions. One of the basic axioms of economic rationality is “Independence of Irrelevant Alternatives” (IIA), according to which a preference ratio between two options should be unaffected by introducing additional alternatives to the choice set. To investigate the biological mechanism for (in) consistent behavior we designed simple decision-making tasks that test IIA violations in C. elegans (See our pre-print: “Bounded rationality in C.elegans”).

By involving in the choice process defined neuronal networks (this is impossible or close to impossible in other organisms!) we tested whether particular neuronal architectures are prone to producing irrational choices. We also genetically manipulated the circuits to make the worm rational or irrational. By probing multiple neuronal architectures using various choice sets, we found that asymmetric sensation of odor options can lead to violations of rationality. We developed a normalization-based mathematical model of value coding and gain control, which explains why only specific network configurations give rise to inconsistent decision making. These studies generated for the first time a law that explains when irrationality occurs, based on mechanistic understanding of the neurons that execute the decisions. We suggest this law as a general example for how neuronal constrains give rise to bounded rationality.