Sensitivity of a Consumer-Grade Electroencephalography Headset and Portable Heart Rate Variability Monitor for Detecting Acute Changes in Mental Workload: Validation Using a Stroop Test Protocol

Objective mental workload measurement in naturalistic and applied settings requires portable, unobtrusive tools that are sensitive to psychophysiological change. This study evaluated the sensitivity of three portable measurement tools to acute changes in mental workload induced by a validated Stroop test paradigm. Firstly, a consumer-grade electroencephalography (EEG) headset (MUSE, InteraXon Inc.), secondly, a chest-strap heart rate variability (HRV) monitor, and thirdly a iPad psychomotor vigilance test (PVT). Thirty-four healthy adults participated in a within-participants protocol in which EEG theta power, HRV indices (SDNN, RMSSD, LF Power, HF Power), PVT performance, and subjective workload (NASA-TLX) were recorded before, during, and after completion of an electronic Stroop test (EncephalApp Stroop). Friedman tests revealed significant changes in theta power across the three time points (?2(2, n = 26) = 33.54, p < .001), with pairwise comparisons confirming significant elevation during the Stroop test. Key HRV indices (SDNN, RMSSD, LF Power) were significantly reduced (P< .05) during the Stroop test compared to baseline. PVT performance did not differ significantly between pre and post-Stroop test periods. Both EEG and HRV measures returned to near-baseline levels within the five-minute post-task recording period: theta power did not differ significantly between the Pre and Post Stroop test periods (p > .05), and no HRV measures differed significantly between Pre and Post Stroop test values (all p > .05). The MUSE EEG headset and portable HRV system were therefore sufficiently sensitive to detect acute changes in mental workload, whereas the PVT was not. The most important implication is methodological in that the paced breathing at 0.1 Hz required by the standard HRV measurement protocol may itself accelerate autonomic recovery and thereby mask residual mental workload. Post-task HRV recorded under paced breathing should therefore be interpreted with caution in mental workload research.