Reliability Assessment of Wearable Technologies for Physiological Measurements: An Evaluation of Shimmer3 GSR+, Empatica E4, EmbracePlus, and Pixel Watch 2 Across Cognitive, Affective and Physical Activity Tasks.

Wearable sensing has evolved from custom-built systems towards standardized research- and consumer-grade devices, improving accessibility and comparability in physiological data analysis. Wrist-worn sensors offer non-invasiveness, minimal setup, and suitability for everyday use, making them increasingly attractive for both research and real-world applications. However, it remains unclear how consumer-grade smartwatches compare with established research-grade wearables in physiological data quality and suitability for empirical studies. We present a mixed-methods study assessing the signal comparability and reliability of the research-grade Shimmer3 GSR+, Empatica E4, and the consumer-grade Pixel Watch 2 under controlled conditions including baseline, cognitive load (n-back), startle, relaxation and physical activity phases. A second study replicated key conditions to exploratorily compare the Empatica E4 with its successor, EmbracePlus. All wearables reliably captured pronounced physiological changes between distinct experimental conditions, but were less sensitive to subtle cognitive load differences and varied in absolute values and motion robustness. The Pixel Watch 2 effectively captured heart rate and skin temperature trends in dynamic settings, whereas research-grade devices remained preferable for analyses requiring raw data access, transparent data processing and advanced physiological metrics. Electrodermal activity provided the most consistent task differentiation under motion. Wrist-worn devices were perceived as more comfortable and less obtrusive than finger-based sensors.