Exploring the effects of indoor temperature on college students physiological responses cognitive performance and a concentration index derived from EEG signals

Experimental studies were done on college students in a climate chamber and analyzed the scenes of measured skin temperature, EGA activity, and task performance of subjects exposed to three temperatures. The concentration performances of the subject task were evaluated by measured neurophysiological parameters. Results showed that there were gender differences in local skin temperatures and EEG-based concentration index at the indoor temperatures to which they were exposed, females’ mean skin temperature is more sensitive to temperature steps. The concentration index was more affected by cold in the male subjects. Experimental results strongly confirmed that the EEG-based concentration index should be affected by indoor temperatures.

Most of the young students' activities are performed indoors. That’s why indoor environmental quality is closely related to their physical state and performance. E.g.  Chinese higher education enrollment experienced a rapid increase over the last decades, reaching 41.8 million by 2020. Universities have expanded or renovated many academic buildings focusing on creating an excellent cultural environment on campus but have neglected to improve and enhance the indoor thermal environment. Problems such as high temperature, poor environmental quality, and poor ventilation often occur in classrooms or study rooms. Students learning efficiency will ultimately be affected at the expense of the quality of the indoor environment, especially the quality of the thermal environment. The relationship between built indoor environment quality and exposure-related physical and cognitive performance has gained rising attention in a recent study. The collaboration between indoor environment design and physiological disciplines is expected to better understand how the thermal environment influences the occupants’ productivity performance, which can help improve the indoor environment at the early design stage from an improving thermal comfort and activity efficiency perspective.

 A large number of previous works investigated how indoor environmental factors such as indoor air quality, acoustic, lighting conditions, and temperature affect occupants’ thermal comfort and productivity. Previous work found that temperature may be perceived as an environmental incentive to exert conscious effort at temperatures outside the comfort zone. previous studies suggest that cognitive task performances for workers and students can be evaluated through psychological metrics.  For example, environmental psychology studies recommend cold color hue of classroom walls in terms to improve the performance of the students’ cognitive activities.

Indoor thermal directly affects human thermal comfort and efficiency. The present study aims to investigate the effects of indoor temperature on college students’ physiological responses. Three indoor temperatures 30 °C, 26 °C, and 22 °C were designed as the test conditions, and temperature-induced changes of subjects’ local skin temperature and EEG signal were analyzed. And one experiment was done…..which was………… The experiment recruited 30 college students in the age group of 20–27, 15 female and 15 males (Average age: 23.5, Height range: 160–185 cm, Body mass: 48–78 kg, BMI:18.8–22.8) all from Qingdao University of Technology, China. All participants were healthy and had no color weakness, neurological deficits, or allergy diseases. In addition, the adolescents were informed to get enough sleep and abstain from alcohol, tea, and coffee before participating in the experiment. They were instructed to wear summer clothing including short sleeves, comfortable sweatpants, socks, and shoes during the test period, the clothing insulation was 0.7clo.

 Conclusions:

Poor indoor environmental quality may suppress students’ physiological responses, leading to learning efficiency loss. 

The main conclusions of this study are as follows:

1.

After experiencing temperature steps, local skin temperatures of the female group were more sensitive to indoor temperature change than the male group. It was found that subjects wear summer clothing with a thermal resistance 0.7 clo, the female group showed more significant skin temperature variations during the experimental procedure.

2.

Through EEG-based concentration index distribution analysis under different indoor temperatures, the average concentration index was affected by temperature differences, the male group showed a more significant cold resistance performance and less ability to heat stress.

3.

Indoor temperature can influence the EEG Beta rhythm of the subjects, concentration index was affected by the exposure temperature, its mean value was highest under 26 °C temperature.

4.

Relatively warm or cold indoor temperature-induced longer response time and lower accuracy while subjects performed cognitive tasks, leading to decreasing performance index. The differences in the two indicators highly depend on the type of cognitive task.

5.

The EEG-based concentration index correlated closely with occupants’ performance index. Thus, it can help maintain relatively high performance by improving indoor thermal comfort design.

Future work will investigate the physiological responses of a similar experiment under a heating environment, and conduct the performance in more types of task tests.