Rationality self-organizes beyond subjective reasonings through the coupling of brain and internal organs

The somatic marker hypothesis proposes that internal bodily activity (IBA) is a prerequisite for rationality. However, the underlying mechanism remains unclear. First, we reveal that IBAs directly switch or lock the output of a neural circuit involved in decision-making, through human and computational studies of binocular rivalry, which is a form of perceptual decision-making. Then, through computational studies of a gambling task, we demonstrate that, if the IBA parameter is updated appropriately based on a subjective evaluation of the decision outcome, a neural network coupled with IBA can converge to rational decisions. Throughout the entire decision-making process, “Brownian ratchet” emerges, forcing unprofitable options to change while enabling rational and profitable decisions to persist. This ratchet enables intersubjective rationality to self-organize beyond subjective reasonings.