Nervous System Intelligence (NSI) Theory: Biological Substrates of Change That Holds; Mechanistic Hypotheses

This paper is the third in a three-paper theoretical series advancing Nervous System Intelligence (NSI) Theory, a constraint-based framework for understanding when and why human change stabilises rather than reverts. While NSI Theory I formalised the architectural constraints governing readiness for durable reorganisation (“change that holds”), and NSI Theory II established recovery-first inference rules for distinguishing transient improvement from anchor-level change, the present paper advances mechanistic hypotheses regarding how these constraints may be biologically instantiated. Drawing on systems biology, neuroscience, physiology, and developmental science, the paper proposes that readiness, anchor stability, and lawful growth sequencing emerge from coordinated activity across bioenergetic–neurophysiological capacity, autonomic–endocrine regulation, long-timescale biological calibration, and predictive learning systems. Rather than introducing novel mechanisms, it specifies how established biological processes may jointly carry and enforce the architectural constraints described in earlier papers. The central claim is that durable transformation is governed not by experience, insight, or performance under load, but by recovery dynamics following perturbation. The paper introduces a perturbation–recovery scaffold as a minimal epistemic structure for inferring readiness and integration without presuming specific interventions or measurement tools. From this scaffold, a set of testable predictions and adjudication criteria are derived. NSI Theory is presented as a biologically grounded hypothesis space rather than a completed mechanistic model. The work is intended to support empirical research, theoretical integration, and more precise inference in domains concerned with psychological change, recovery, development, and adaptation. Author Terminology Update as of 31 January 2026 This paper was published under the term Nervous System Intelligence Theory. The theory is now situated within the broader framework of Human Operating System Architecture (HOSA), reflecting expanded scope and interdisciplinary applicability. The underlying mechanisms, principles and claims remain unchanged.