From taxonomy to calculus: EICI and the problem of adaptive rationality

This position paper responds to Bhui et al. (2026, PsyArXiv) — "The roots of rationality" — which identifies six adaptive dynamics across timescales but acknowledges the absence of a formal constraint preventing universal rationalization. The ISHEA EICI framework (EICI = E × I / F), calibrated empirically across biological, cognitive, and socioeconomic domains, provides that constraint. The paper demonstrates structural complementarity between the two frameworks, presents the K-Model biological instantiation (K = K₁ × K₂^(1/2); NAD⁺/ROS/ATP), and argues that coherence — not optimality — is the measurable condition underlying adaptive success. Validated against UK Biobank NMR data (n=250,241). OSF parent project: 10.17605/OSF.IO/4K9JZ.

This working paper positions the ISHEA Energetic–Informational Coherence Index (EICI) in direct dialogue with Bhui et al. (2026), a multi-institutional preprint (MIT, NYU, Columbia, UCL, Brown) proposing a unified taxonomy of adaptive decision-making across six dynamics and multiple timescales. While Bhui et al. offer conceptual synthesis, they explicitly leave open the question of formal constraints. This document provides those constraints via the EICI equation and its empirical calibration. The K-Model (biological instantiation) and the friction variable F (ζ=0.68, panel OLS) are presented as operative answers to the three open questions identified in the Bhui et al. framework. Part of the ISHEA K-Model research cluster. Author: C.J. Pérez Pulido, ISHEA Institute, Bologna.