The Measurement Crisis in Cognitive Warfare Defence: Evaluating Single-Layer Countermeasures across Democratic Societies

State-sponsored cognitive warfare has emerged as a defining cross-national security challenge, systematically targeting the information environments of democratic societies and allied institutions. Yet despite the proliferation of defensive countermeasures since 2020, systematic evidence evaluation remains critically limited. This research examines four major individual intervention categories (prebunking and inoculation theory, artificial intelligence detection technologies, media literacy programmes, and rapid response systems) through structured evidence synthesis applying adapted GRADE criteria. Two research objectives guide the analysis: evaluating empirical evidence quality and identifying measurement limitations that systematically overestimate operational effectiveness; and analysing performance gaps between laboratory conditions and real-world deployment. Evidence reveals substantial variation in empirical support across countermeasure categories. Prebunking demonstrates the strongest evidence base, with large-scale field studies showing 55-60% improvements in manipulation detection. AI detection systems show 45-50% accuracy degradation from laboratory to operational conditions due to adversarial adaptation. The research identifies a fundamental measurement problem: over 89% of studies analysed measure capabilities rather than behaviours, creating systematic overestimation of intervention effectiveness. These findings provide evidence-grounded guidance for national security planners, defence ministries, and NATO member states allocating resources to cognitive defence, emphasising behavioural validation as a prerequisite for operational confidence.