Figure 3. Sequence scheme over time of image presentation in terms of arousal and valence levels.

The y axis relates to the official IAPS score, whereas the x axis relates to the time. The neutral sessions, which are marked with blue lines, alternate with the arousal ones, which are marked with red staircases. Along the time, the red line follows the four arousal sessions having increasing intensity of activation. The dotted green line indicates the valence levels distinguishing the low-medium (L-M) and the medium-high (M-H) level within an arousing session. The neutral sessions are characterized by lowest arousal (<3) and medium valence scores (about 6).