Difference of thermal patterns of the face and neck regions in states of physical and mental stresses
Authors: Zhumazhanova S.S. 
Published: November 2021

Systems for remote detection of a person's state today have enormous potential, but the identification features of states in each system are different. States of mental and physical stress have a huge impact on the performance of the operator's work tasks, and it is important to distinguish between them. The purpose of the work is to review research on identifying states of physical and mental stress by analyzing the temperature of the subject's face and body; conducting experiments aimed at inducing a state of mental stress using the Stroop verbal-color test and physical stress after exercise and analyzing the main differences between the states and the perspectives for their use. Significant differences were found between the mean temperatures of the areas under physical stress and the standard deviation of temperatures under mental stress. The research results can be applied in applications, monitoring systems for the state of operators of complex technical and technological facilities. Stress is as a high level of emotional arousal, usually associated with mental or physical stress. To determine the stressful state of a person, a continuous analysis of physiological signals – ECG, EEG, skin temperature, respiratory rate is carried out. To overcome the limitations associated with the use of contact sensors for recording physiological parameters, methods of computational psychophysiology based on IR-imaging have been used recently. A review of the work on the formation of a thermal picture during and after physical and mental stress is provided. Experiments were carried out to register changes in the thermal patterns of the face and neck regions of 84 subjects after physical exercises and in a state of mental stress when passing the Stroop verbal-color test. A technique for automatic detection of 26 anatomical areas of face and neck regions was developed. The average value and standard deviation of temperatures of all selected areas of the face and neck regions in a state of physical stress are lower than in other states. The lowest temperature in a state of physical stress is observed in the area of the face under the nose and above the lip, which can be explained by the increased respiratory rate that occurs during and after exercise. In general, the low temperature readings compared to other conditions under consideration can be explained by increased sweating, lowering body temperature and narrowing of the lumen of blood vessels observed during exercise. Under mental stress, the average temperature values remain the same as in normal state, however, the standard deviation exceeds the same values during stress when passing the Stroop color test. Such leaps are especially noticeable in areas No. 5 and 6 – the inner corners of the eyes, as well as No. 21 and 22 – the area of the face under the nose, which is explained by the concentration of attention during the test and the frequent change in RR (increase/decrease in RR). Accounting for such changes will help expand the capabilities of new applications for assessing the current state of the subject.