Neural-Cycle Periodicity Across Political Systems: Cross-Civilizational Verification of the NCHR Framework in Democratic, Authoritarian, Theocratic, and Transitional Polities

This paper extends the Neural-Cycle Historical Rhythm (NCHR) framework to a cross-civilizational sample of 34 executive tenures drawn from four distinct political system types: the United States (15 post-war presidential terms), the Soviet Union and Russia (9 leaders), Iran (3 Supreme Leaders including the 2026 succession), and Ukraine (7 presidents). The framework's core claim—that the four prefrontal cortex maturation transitions at approximately 15, 30, 45, and 60 years generate predictable behavioral periodicities in political leaders across geographic, cultural, and ideological boundaries—is tested against independently verifiable historical events at each node. T4 cognitive fixation rates vary systematically by political system type: United States 72.7%, Soviet Union/Russia 87.5%, Iran and Ukraine both 100%. Seven cross-civilizational regularities are identified, including the universal T2 activation pattern and the T4 cognitive fixation threshold. The 2022 Russo-Ukrainian War falls within one year of a PPCL 60-year node, constituting cross-scale resonance between individual T4 fixation cycles and civilizational periodicity. The 2026 succession in Iran following the assassination of Supreme Leader Khamenei is analyzed as a real-time test case.