Operationalizing the physiological state (P) in nonlinear behavioral systems: a measurement framework for state-dependent dynamics

Abstract

Behavioral outcomes may vary within the same individual even when measured environmental conditions appear comparable. To test whether an organism’s changing physiological condition provides information about such variation, this article proposes an operational measurement framework for Physiological State ( P). P is defined as a latent, multidimensional, and time-dependent configuration generated by ongoing Physiological Organization. Antecedent conditions ( A ) and consequence-related conditions ( C ) remain external environmental variables, whereas behavior ( B ) is modeled as a separate downstream outcome. Rather than uniquely determining behavior, P influences Physiological Accessibility—the state-dependent availability of existing Adaptive Capacities for recruitment and use—and thereby constrains behavioral expression. The construct is distinguished from emotional and cognitive constructs, subjective reports, observable behavior, stress, allostatic load, and individual physiological indicators. Operationalizing requires prespecifying the target behavior and timescale; selecting reliable, sensitive, feasible, and nonredundant physiological indicators; aligning and preprocessing observations; deriving dynamic features; integrating those features through an identifiable latent-state model; representing estimated uncertainty; and conducting prospective validation. The Thirteen Physiological Systems and Seven Layers of Physiological State guide physiological coverage and interpretation but do not correspond one-to-one with the latent dimensions. In a candidate nonlinear state-space implementation, physiological observations, Y (t), provide evidence for estimating P (t), while state evolution depends on preceding P, current A , and relevant prior C . Filtered estimates use only information available through the prediction time. Because B remains outside the physiological observation vector and is evaluated prospectively as B (t + Δ), the framework avoids circularly defining the state by the outcome it is intended to predict. Empirical support would require reliable, interpretable, and temporally coherent state estimates that demonstrate reproducible prospective and incremental value beyond environmental variables, prior behavior, isolated physiological indicators, established single constructs, simple physiological composites, and appropriate linear or lower-dimensional alternatives. Failure to obtain identifiable state estimates or incremental prospective information about B would count against the proposed operationalization. The framework is theoretically and methodologically developmental and should not be interpreted as a validated instrument, diagnostic measure, or universal physiological score.

The authors' abstract, as published at the source. Frontiers in Psychology, 2026 · DOI ↗