Delving beneath the surface: A systematic review of human experience of indoor thermal environments through electroencephalogram (EEG)

This comprehensive review delves into Electroencephalogram (EEG) applications for assessing human experiences in thermal environments, focusing on thermal perception, cognition, and emotions. Our analysis categorizes EEG studies into statistical investigations and discrimination models. Statistical studies, encompassing various frequency bands and indices, yield inconclusive outcomes due to diverse findings. Discrimination models employ a diverse range of EEG features tailored to specific experimental conditions. The lack of a consistent knowledge foundation on EEG's spectral and topographical properties to distinct aspects of human thermal experience, along with the absence of a universally recognized thermal perception index and variations in defining cognition and emotion indices, contributes to this diversity. Through a thorough examination of methodological aspects, including experimental and data analysis approaches, our review exposes significant gaps and limitations in current thermal experience research. The paper proposes key recommendations to advance the field, emphasizing the importance of a comprehensive environmental portrayal, standardized perceptual descriptors, multidomain studies, and dynamic thermal research. Advocating for investigations into individual thermal variable influences, within-subject experiments, and addressing cognitive interferences, the review also highlights the need for improved data granularity, standardized EEG protocols, and a broader exploration of EEG analysis methods. Addressing these aspects is vital for establishing a more consistent knowledge base, enhancing research reliability, and improving result communication. Our findings contribute to a deeper understanding of human thermal experience, providing recommendations to bridge identified gaps and limitations, fostering a more robust foundation for future research in this domain.