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

Psychological evidence shows that updating the rhythmic, internal body activity (IBA) based on the decision outcome is important to have a rational decision-making in a gambling task. However, the detailed mechanism how body guides rationality remains largely unclear. This paper provides a comprehensive theory that bridges the rhythmic coupling between the brain and internal organs and the rationality in a gambling decision-making task. Through our study of human binocular rivalry, we show that IBA creates the decision-switching (Sw) and -locking (Loc) phases based on the IBA parameters such as frequency, amplitude, and mean activity. When applied to a gambling task, the Sw-Loc structure creates directionality within the expected-value space of the decision options, wherein only options with expected values aligned with that directionality are stabilized. The stable direction can flip by changing how the IBA is updated in response to a decision outcome (e.g., taking a deeper or shallower breath). Using a theoretical analysis of a Brownian particle in a two-state heat bath, we show that the Sw region induces a large first-passage decision bias based on the random decision switching rate. Then, the Loc region acts as a rectifier, allowing only options with expected values aligned with the stable direction to persist. The rhythmic coupling of a brain and internal organs creates a directed medium that absorbs and separates external information, inducing biased decision-making through randomness.