Non-Invasive Physiological Metrics for Cognitive Load Assessment in Training and Operational Contexts: Signal Processing, Evidence, and Feasibility.
Level 5 - mechanism / opinion, no new human data
Structured narrative review synthesizing primary studies and reviews without a formal systematic review protocol or meta-analysis.
PubMed 42590624 · doi:10.3390/s26154848
What was done
Authors conducted a structured narrative review searching Google Scholar, PubMed, Scopus, Web of Science, and IEEE Xplore for literature published between January 2021 and February 2026. The review synthesized 37 sources (25 primary empirical studies and 12 systematic reviews or meta-analyses) to evaluate non-invasive physiological metrics—including cardiovascular (HR/HRV), respiratory, EEG, fNIRS, ocular, and electrodermal activity—for cognitive load assessment across training, simulated, and operational contexts.
What was found
Across the 25 primary studies, cardiovascular metrics were evaluated most frequently (16 of 25), followed by EEG (11 of 25), ocular metrics (9 of 25), electrodermal activity (8 of 25), fNIRS (3 of 25), and respiratory metrics (3 of 25). EEG frontal theta showed the strongest meta-analytically supported link to cortical processing but remains constrained by motion artifacts and setup demands. Wearable cardiovascular and electrodermal signals offered high field readiness but low specificity, reflecting generalized autonomic/sympathetic activation rather than isolated cognitive load. The abstract does not report pooled quantitative accuracy statistics or effect sizes.
Why it matters
This review highlights the persistent trade-off between signal specificity and field feasibility in cognitive workload monitoring. It establishes that single-sensor approaches are inadequate and provides a framework for pairing complementary sensing modalities based on context and signal processing constraints.
Limits
As a narrative review, it lacks a formal meta-analytic synthesis, systematic risk-of-bias assessment, or pre-registered protocol. The abstract reports study counts across modalities but omits human participant sample sizes, population characteristics, and quantitative diagnostic performance metrics.