Response pattern analysis of human cognitive performance under continuous humid heat exposure

Cognitive decay is an important aspect of health problems caused by exposure to moist heat. In the course of previous research by scholars, objective cognitive performance is often used to evaluate changes in cognitive ability. Cognitive performance refers to the efficiency of information processing in the human brain, which is indicated by speed, accuracy, and attentional demand. It has been found that heat stress induced by humid heat exposure affects the functioning of the nervous system, which leads to reduced cognitive performance and impaired cognitive ability.Bruce-Low et al. pointed out through a pilot study that increased ambient temperatures cause changes in heart rate variability, which increases anxiety levels, impairs mood and creativity, and cognitive performance.Cui et al. and Cian et al. conducted a reaction time and memory test at high temperatures (32, 45 °C), respectively. Reaction time and memory tests were performed at high temperatures and similarly observed an increase in mean reaction time and found that the maximum string length obtained in short-term memory tests at high temperatures was significantly reduced. However, there are a few studies that have yielded different results, such as Jiang et al.'s study that demonstrated no significant change in subjects' correctness on a pattern matching test at 50 °C compared to 22 °C, and Vasmatzidis et al.'s study that showed no significant change in subjects' overall cognitive performance did not show significant changes.

In the field of built thermal environment research, the effects of the physical environment on human thermal comfort and thermal sensation have been suggested to contribute to changes in cognitive performance.Lan et al. found that a partial-heat environment significantly reduces human cognitive performance by decreasing subjects' thermal comfort and exacerbating Sick Building Syndrome (SBS).Liu et al. similarly demonstrated that, after 45 min of moderate-intensity exercise in an environment at 37 °C, the Subjects' accuracy on tests of semantic interference and visual perception was significantly reduced, but reaction speed became faster.Wyon et al. summarized the association between ambient temperature and cognitive performance, proposing that three factors, namely, reduced attention induced by thermal discomfort, enhanced SBS, and reduced arousal level caused by diminished metabolic heat production, cause cognitive performance to be attenuated.

In addition to the laboratory studies mentioned above, a field study of soldiers' cognitive performance in an actual desert environment showed that hot climates cause impaired cognitive performance, especially for cognitive abilities that require sustained attention, neuromotor abilities, verbal memory, and executive functions. In addition, a survey of office typists found that male subjects were significantly less likely to be correct when entering text at 33 °C, and were significantly less likely to be correct on pattern recognition and spatial span tests at 50 °C than at 20 °C.

Based on the above analysis, it can be seen that current research has found that hot and humid environments affect human cognitive performance by influencing human neurological function, as well as human subjective thermal comfort and thermal sensation, which ultimately lead to cognitive impairment. However, current research tends to use a limited variety of tasks (one to three cognitive tasks) to study human cognitive changes, and there is a gap with the multiple cognitive demands that people actually face on a daily basis. Meanwhile, the duration of exposure to moist heat needs to be extended to better observe the pattern of cognitive changes under continuous moist heat exposure. In addition, due to the limitation of hygrothermal exposure, the current research generally focuses on thermal exposure, and the research on hygrothermal exposure needs to be supplemented. Considering that people may often face multiple cognitive tasks with simultaneous stimulation in their daily work, this paper chose five different types of cognitive tasks to study the changes in subjects' cognitive performance when they were continuously exposed to four different kinds of humid-heat environments and dealt with multiple cognitive tasks. The innovation of this study lies in the method of continuous stimulation with multiple cognitive tasks to explore the changing law of cognition under humid-heat exposure.

Compared with the single task or one to three types of tasks in the current state of research, multiple cognitive tasks are more in line with the real situation of cognitive needs in people's daily life and work, so this study has more practical value; in addition, we focused on observing the changing law of cognitive performance over exposure time with the multiple cognitive tasks and continuous stimulation under humid-heat exposure, and this study is more useful. In addition, we focused on observing the change pattern of human cognitive performance with exposure time under multiple cognitive tasks and continuous stimulation of humid-heat exposure, which is often neglected in the current research. Under the current background of global warming, this study is of theoretical significance for deepening the understanding of the change pattern of human cognitive performance and even work efficiency under hot and humid exposure, as well as the environmental intervention technology of cognitive decay.