# Stress Analysis with Dimensions of Valence and Arousal in the Wild
## 3 SADVAW Dataset and Stress Analysis
### Annotators and Evaluation Process  
A total of 27 (12 males and 15 females) college students, with ages ranging from 21 to 26, voluntarily participated in this study. They were asked to evaluate and annotate for video clips in the dataset with nine scales for each class (stress, valence, and arousal). They had no history of mental or psychiatric ailments. The participation criteria also required candidates to not be under medication, even for simple illnesses, such as the common cold because health and mental issues can affect the emotional perception of the characters in the video. The annotators were trained before carrying out the evaluation. They were instructed to immediately and quickly judge the facial expressions for emotion labels as they felt and were told to avoid making a conscious effort to respond. They were also prohibited from any discussion with others to avoid any bias or influence.  
Figure 1: Structure of an LSTM unit.  
Figure 2: Examples of different scores of valence, arousal, and stress in the SADVAW dataset. The first four rows present examples for stress values, the next four rows include examples for valence values, and the last four rows show examples for arousal values. Each row consists of the sequence of frames of a video with the corresponding annotated value on the left. The value range of stress, valence, and arousal is from 1 to 9. Here, we only present the videos with some representative values (2–4–6–8) for each class.  
Annotation sessions were conducted for 3 h each in the morning and afternoon for 2 days. The evaluators were divided into two groups. The first group (14 people) evaluated on the morning of the first day and the second day's afternoon. The second group (13 people) evaluated on the afternoon of the first day and the morning of the second day. Annotators rated each video clip on a nine-point scale, where the range (1 to 9) represents the least positive to the most positive, the least agitated to the most agitated, and the least stressful to the most stressful, for valence, arousal, and stress, respectively (see Table 2). For example, Figure 3 illustrates some examples of a frame in video clips in the SADVAW database, along with their corresponding annotations. At the top-left of Figure 3, the man is looking towards the woman with a cheerful and happy smile. According to the evaluated values, the man was in an active state, without stress, and had a low agitation level. In Figure 3, at bottom-left, the girl was cautious of someone, showed a little nervousness, and was therefore evaluated for neutral stress, valence, and stress. Similarly, people in Figure 3, at top-right and bottom-right, were evaluated for high stress, high level of agitation, and valence of negative status.  
We computed the average value, median, and average of the values within the range of two standard deviations (\(\pm 2\sigma\)) [26] around the mean for each video clip, which 27 people evaluated. The results show that the calculated values were similar or differed slightly. Therefore, we chose the values within the mean \(\pm 2\sigma\) range as ground truth.