Experimental protocol. Participants sit on a chair in front of a display. After the experimenter exits the room, a gray screen is shown for 5 minutes. Then, each video is presented for 10 minutes. After 8 minutes, the experimenter enters the room and participants are told to fill in the questionnaire. The order of the videos is at random. Physiological indices at the last 3 minutes of the gray screen period are used as baseline. The period of 5 minutes to 8 minutes during video image presentation is used to measure response.