Emotional Stress Assessment Using Facial Thermal Imprint

Thermal imaging is one of the most promising methods of probing the psychological status of human beings because of its non-invasiveness. This study develops a new method of assessing the emotional stress status in real time. The differential temperature between philtrum and forehead (DTPF) algorithm is developed to extract stress-induced thermal imprints. The correlation between the extracted thermal imprints and established stress markers is significant. Experimental result demonstrates that DTPF has the capacity to classify stress and baseline status. Introduction Stress is having increasingly strong effects on the human health. Stress assessment has been actively conducted using various methods. Despite the complicated chem electronic analysis procedure, salivary cortisol concentration has been widely accepted as the biomarker of activation of the hypothalamic–pituitary–adrenal (HPA) axis, which is directly linked to stress[1][2]. Various studies have been performed on stress, including public speaking[3], cognitive task[4], and emotion induction[5][6]. Unlike established stress markers such as HPA axis end-product cortisol, the imaging system has the advantages of non-invasiveness, versatility and reliability. The literature on the remote sensing of stress continues to increase. Pavlidis first observed the thermal signature of startle and reported that the instantaneous blood demand increases in periorbital region[7][8][9][10]. Aside from the thermal infrared (IR) system, functional magnetic resonance imaging (fMRI) assesses human emotion by monitoring information on the oxygen consumption of areas in the brain, which is activated during the onset of a specific emotion, experience, thought, or action. Although stress has been studied quite extensively, the challenges persist because the methods involved require substantial cooperation from the participants. The baseline problem is another major challenge for the real time stress assessment. Effective solutions will not be easily achieved and will require not only analyses of the quantitative linkages between electro-optical properties and human stress, which is the focus of the present study. For psychological signals the problem involves finding a condition against which changes in measured signals can be compared (i.e., a state of calmness or baseline). To address the aforementioned challenges, we developed a new psychological signal extraction algorithm. The algorithm is based on the differential temperature between different facial thermal imprint. In this study, 41 healthy males and females underwent TSST (Tier Social Stress Test) in a controlled lab. Facial thermal images were collected during the experiment, with established stress markers, such as HBR and cortisol level. Statistical tests were then applied to analyse the resulting set of dependent variables over time. The correlation analysis explored the relation between thermal imprints and established stress markers for characterizing the different phases of the stress cycle. Materials and Methods Participants The participants in this project were recruited mainly by posting ads on a newspaper. A total of 41healthy volunteers participated in the experimental trials. The experimental protocols were in the order of TSST.