In the face of stress: Interpreting individual differences in stress-induced facial expressions

You look stressed: A pilot study on facial action unit activity in the context of psychosocial stress

Quality and quantity of the human stress response are highly individual. Not only are there differences in terms of psychological and physiological stress reactivity, but also with regard to facial muscle stress reactivity. In a first correlative pilot study to decipher the signature of stress as it presents in the physiognomy of a stressed individual, we investigated how stress-induced muscle movement activity in the face is associated with stress marker activation during a standardized laboratory stress test. Female and male participants (N = 62) completed the Trier Social Stress Test and provided multiple measurements of salivary cortisol, subjective experience, heart rate, and high-frequency heart rate variability. In addition, participants were filmed during stress induction to derive the activation of 13 individual muscles or muscle groups, also termed action units (AU). Mean AU intensity and occurrence rates were measured using the opensource software OpenDBM. We found that facial AU activity correlated with different aspects of the psychosocial stress response. Higher stress-induced cortisol release was associated with more frequent upper eyelid raiser (AU05) and upper lip raiser (AU10) occurrences, while more lip corner pulling (AU12) went along with lower cortisol reactivity. More frequent eyelid tightener (AU07) occurrences were linked to higher subjective stress reactivity but decreased heart rate and HF-HRV reactivity. Last, women showed greater stress-induced smiling intensity and occurrence rates than men. We conclude that psychosocial stress reactivity is systematically linked to facial muscle activity, with distinct facial stress profiles emerging for different stress markers. From all the AUs studied, eyelid tightening (AU07) seems to provide the strongest potential for future attempts of diagnosing phases of acute stress via facial activity.

Going Deeper than Tracking: A Survey of Computer-Vision Based Recognition of Animal Pain and Emotions

Advances in animal motion tracking and pose recognition have been a game changer in the study of animal behavior. Recently, an increasing number of works go ‘deeper’ than tracking, and address automated recognition of animals’ internal states such as emotions and pain with the aim of improving animal welfare, making this a timely moment for a systematization of the field. This paper provides a comprehensive survey of computer vision-based research on recognition of pain and emotional states in animals, addressing both facial and bodily behavior analysis. We summarize the efforts that have been presented so far within this topic—classifying them across different dimensions, highlight challenges and research gaps, and provide best practice recommendations for advancing the field, and some future directions for research.

Event-related driver stress detection with smartphones among young novice drivers

Complex and diverse driving situations can pose short-term stressors to novice drivers. Continuously detecting stress is essential for driver training, stress intervention, and the design of in-vehicle information systems. This study designed and validated a driver stress detection method at the event level based on machine learning algorithms and facial features captured with smartphones. Thirty young novice drivers completed two driving tasks containing eight events of two versions (neutral and stressful), with psychological, physiological, and facial data collected. Four combinations of input data types and six machine learning algorithms were used to detect stressful events. The KNN algorithm with facial plus individual profile features yielded the highest accuracy of 89.2%. Adding individual profile features can improve classification performance. Facial areas such as brow, eye, jaw, nose, and mouth were most sensitive to stress. This approach could provide more temporal-spatial information about the driver's stress levels during the whole driving process. Practitioner Summary: This paper proposed a method to detect driver stress at the event level with smartphones. Models with facial plus individual profile features and the KNN algorithm had the most outstanding classification performance. The presented approach can serve as a tool for improving in-vehicle interaction system design when considering driver stress. Abbreviations: GSR: galvanic skin response; ECG: electrocardiography; HR: heart rate; HRV: heart rate variability; RGB: red green blue; NIR: near-infrared; IP: individual profile; DSI: driver stress inventory; APS: arousal predisposition scale; API: application programming interface; PPG: photoplethysmography; EDR: electrodermal response; PD: pupil diameter; SCL: skin conductance level; RF: random forest; KNN: k-nearest neighbour; LDA: linear discriminant analysis; QDA: quadratic discriminant analysis; SVML: support vector machines with the linear kernel; SVMP: support vector machines with the polynomial kernel; TP: true positive; TN: true negative; FP: false positive; FN: false negative; t-SNE: t-distributed stochastic neighbour embedding.

Social Acts and Anticipation of Social Feedback

Socialization happens so regularly in humans that it can be perceived as an effortless activity. However, it reflects a sophisticated behavior, pervaded by anticipation and emotion. The fast-paced social interplay, strongly mediated by facial expressions, can be considered one of the most frequent high-order motor acts within the human behavioral repertoire. The ability to adequately process social feedback is critical for appropriate socialization and affects well-being. The social difficulties often observed in psychiatric patients highlight the link between mental health and successful socialization and the importance of characterizing the behavioral and neural mechanisms of social interaction. This chapter will present some cross-species evidence on the cortical regions engaged during social interactions including facial expressions, and the impact of induced or perceived social stress on the experience of social interactions.

Negative self-evaluation induced by acute stress indexed using facial EMG

Maladaptive stress responses are a key feature of several psychiatric disorders, but findings of stress effects on social behavior are inconsistent. Using a within-subject design, we investigated, in 35 healthy participants, the effects of acute stress on psychophysiological and behavioral responses during a simulated online social interaction task. Participants were exposed to established stress and non-stress exposure procedures in two separate sessions. During the task, participants liked or disliked pictures of other putative players and, similarly, saw their own picture being judged by others. After stress exposure, corrugator muscle activity (frowning) was significantly increased when participants saw their own picture while anticipating feedback from others. Consistently, zygomatic muscle activity (smiling) for self-evaluation was lower after stress than in the non-stress session. We found self-report of stress to be a significant predictor of corrugator activity in both sessions, indicating that higher levels of subjective stress overall were accompanied by increased negative self-evaluation. Surprisingly, no stress effects were found on behavioral measures of other-evaluation (i.e., percentage of dislikes to others), but corrugator response significantly predicted the percentage of dislikes during the stress session only. Overall, our findings suggest that stress increases negative self-evaluation as indexed by elevated corrugator activity. Furthermore, stress might sharpen the consistency between corrugator activity and negative evaluation of others. Our results indicate that negative self-evaluation might be a useful therapeutic target in patients with stress-related psychiatric disorders. In this context, facial muscle activity may be an adequate biomarker for identifying stress-related differences in self-evaluation.

Understanding how stress responses and stress-related behaviors have evolved in zebrafish and mammals

Stress response is essential for the organism to quickly restore physiological homeostasis disturbed by various environmental insults. In addition to well-established physiological cascades, stress also evokes various brain and behavioral responses. Aquatic animal models, including the zebrafish (Danio rerio), have been extensively used to probe pathobiological mechanisms of stress and stress-related brain disorders. Here, we critically discuss the use of zebrafish models for studying mechanisms of stress and modeling its disorders experimentally, with a particular cross-taxon focus on the potential evolution of stress responses from zebrafish to rodents and humans, as well as its translational implications.

Improving Mental Health Services: A 50-Year Journey from Randomized Experiments to Artificial Intelligence and Precision Mental Health

This conceptual paper describes the current state of mental health services, identifies critical problems, and suggests how to solve them. I focus on the potential contributions of artificial intelligence and precision mental health to improving mental health services. Toward that end, I draw upon my own research, which has changed over the last half century, to highlight the need to transform the way we conduct mental health services research. I identify exemplars from the emerging literature on artificial intelligence and precision approaches to treatment in which there is an attempt to personalize or fit the treatment to the client in order to produce more effective interventions.

The Correlation between Pain, Stress, and Oral Function in Oral and Maxillofacial Infection and Trauma Patients

Background:

The relationship between stress and acute pain has been documented in previous studies. Yet, very few studies have evaluated the relationship between stress and acute orofacial pain and its impact on jaw functional activities.

Objective:

The objective of the current study was to evaluate the correlation between acute orofacial pain, stress, and the limitation of the jaw and facial activities in oral and maxillofacial infection and oral and maxillofacial trauma patients.

Methods:

The current study recruited 50 (16 male, 34 female) patients from the Emergency Unit of the Ujung Berung Hospital, Bandung Indonesia. Twenty-five patients were those who had oral and maxillofacial trauma, and the rest were those who had an oral and maxillofacial infection. The patient’s stress level was evaluated by measuring their salivary alpha-amylase level, the pain level was measured by using the numeric rating scale (NRS), whilst the limitation of the jaw and facial activities was measured by using the Jaw and Facial Activities Limitation (JFAL) Questionnaire. All data were analysed using the Spearman correlation test.

Results:

Based on the analysis, it was revealed that there was no significant correlation (r = 0.176, p= 0.22) between stress and pain level. When associated with jaw and facial activities limitation, there was a significant positive correlation (r = 0.555, p < 0.01) found between pain level and jaw and facial activity limitation.

Conclusion:

The current study concluded that there was a significant positive correlation found between pain and jaw activity limitation on oral and maxillofacial infection and trauma patients.

Open-plan office noise is stressful: multimodal stress detection in a simulated work environment

The coronavirus disease 2019 (COVID-2019)-induced changes in the workplace present a timely opportunity for human resource management practitioners to consider and remediate the deleterious effects of noise, a commonly cited complaint of employees working in open-plan office (OPO) environments. While self-reports suggest that OPO noise is perceived as a stressor, there is little experimental research comprehensively investigating the effects of noise on employees in terms of their cognitive performance, physiological indicators of stress, and affect. Employing a simulated office setting, we compared the effects of a typical OPO auditory environment to a quieter private office auditory environment on a range of objective and subjective measures of well-being and performance. While OPO noise did not reduce immediate cognitive task performance compared to the quieter environment, it did reduce psychological well-being as evidenced by self-reports of mood, facial expressions of emotion, and physiological indicators of stress in the form of heartrate and skin conductivity. Our research highlights the importance of using a multimodal approach to assess the impact of workplace stressors such as noise. Such an approach will allow HR practitioners to make data-driven recommendations about the design and modification of workspaces to minimize negative effects and support employee well-being.

Effect of transportation and social isolation on facial expressions of healthy horses

Horses have the ability to generate a remarkable repertoire of facial expressions, some of which have been linked to the affective component of pain. This study describes the facial expressions in healthy horses free of pain before and during transportation and social isolation, which are putatively stressful but ordinary management procedures. Transportation was performed in 28 horses by subjecting them to short-term road transport in a horse trailer. A subgroup (n = 10) of these horses was also subjected to short-term social isolation. During all procedures, a body-mounted, remote-controlled heart rate monitor provided continuous heart rate measurements. The horses' heads were video-recorded during the interventions. An exhaustive dataset was generated from the selected video clips of all possible facial action units and action descriptors, time of emergency, duration, and frequency according to the Equine Facial Action Coding System (EquiFACS). Heart rate increased during both interventions (p<0.01), confirming that they caused disruption in sympato-vagal balance. Using the current method for ascribing certain action units (AUs) to specific emotional states in humans and a novel data-driven co-occurrence method, the following facial traits were observed during both interventions: eye white increase (p<0.001), nostril dilator (p<0.001), upper eyelid raiser (p<0.001), inner brow raiser (p = 0.042), tongue show (p<0.001). Increases in 'ear flicker' (p<0.001) and blink frequency (p<0.001) were also seen. These facial actions were used to train a machine-learning classifier to discriminate between the high-arousal interventions and calm horses, which achieved at most 79% accuracy. Most facial features identified correspond well with previous findings on behaviors of stressed horses, for example flared nostrils, repetitive mouth behaviors, increased eye white, tongue show, and ear movements. Several features identified in this study of pain-free horses, such as dilated nostrils, eye white increase, and inner brow raiser, are used as indicators of pain in some face-based pain assessment tools. In order to increase performance parameters in pain assessment tools, the relations between facial expressions of stress and pain should be studied further.