Warmer Environments Increase Implicit Mental Workload Even If Learning Efficiency Is Enhanced

This study investigated how different thermal environments (18, 22, 25, and 29°C) affect cognitive performance, mental workload, and physiological stress over time. While results showed that reading efficiency and task speed improved in warmer conditions, physiological markers such as heart rate variability and skin conductance indicated a significant increase in stress and implicit mental workload. EEG data revealed that concentration-related theta power decreased over time, even as subjective workload ratings rose. The findings suggest that higher room temperatures, like those recommended by Japanese energy-saving policies, may cause hidden cognitive strain despite appearing to facilitate faster learning.