Disgust, Interoception, and the Visceral Self: A Predictive Processing Framework Linking Insular Function to Non-Newtonian Fluid Dynamics

Background: The insular cortex has been implicated in functions ranging from interoceptive awareness and homeostatic regulation to disgust processing and social cognition, yet no unifying account explains this functional diversity. Critically, more than 70% of human body water exhibits non-Newtonian properties—fluids whose viscosity changes dynamically in response to shear through alterations in intermolecular interactions—yet no neurobiological framework has addressed how the brain monitors and regulates these complex fluid dynamics. Methods/Approach: We conducted a theoretical review and synthesis of evidence from neuroimaging, rheology, physical chemistry, autonomic physiology, and interoceptive research to develop an integrative framework of insular function. Principal Findings: This paper proposes that the insula functions as a predictive processor for non-Newtonian fluid dynamics. The insula's posterior-to-anterior organization maps onto the autonomic nervous system's sympathetic-parasympathetic division, which in turn reflects a gradient of non-Newtonian fluid complexity: sympathetic-dominant territories involve simpler fluid dynamics, while parasympathetic-dominant territories—governing glandular secretions, mucosal surfaces, and visceral organs with splanchnic circulation—require modeling pronounced non-Newtonian behavior including yield stress, shear-thinning, and viscoelasticity. The same hierarchical predictive architecture that models concrete fluid dynamics at posterior levels generates increasingly abstract representations at anterior levels—from visceral sensation through emotional awareness to social and moral cognition—paralleling hierarchical processing in artificial neural networks. Significance: This framework explains the insula's involvement in seemingly disparate processes and generates testable predictions. Understanding the insula as a predictive processor of non-Newtonian fluid dynamics provides a novel bridge between visceral physiology, autonomic regulation, and higher-order cognition. Clinical conditions including PTSD, depression, anxiety, OCD, and autism spectrum disorders show distinct patterns of insular dysfunction that may reflect specific failures in predicting or regulating non-Newtonian fluid dynamics—as in PTSD, where overweighted threat priors drive chronic sympathetic dominance that disrupts visceral blood flow and mucosal secretion. This theory may also illuminate a deeper principle: the brain evolved as a predictive engine specifically tuned to the physics of our body—with non-Newtonian fluid dynamics representing a primary domain of this embodied prediction.