Figure 1 Experimental design, including the expected position in the VAD (Valence, Arousal,
Dominance) space. After a five minute initialization with IAPS images, the experiment starts with a
short introduction, followed by the first round of the mental training (ES-1 - ES-5). The second
round of the mental training contains six games (ES-1 - ES-6) and starts after a ten minute-
presentation of IAPS images. The experiment is finalized with the completion of standardized
questionnaires. Our classification categories were ES-2 (orange) vs. ES-5 (turquoise).
2.3 Feature Extraction
We used 4-channel biosignals (2 x EMG, BVP, and SCL) for the emotion
recognition. The signal length is about 3 min for ES-2 and 5 min for EP-5,
representing ...