The experimental group receives video-viewing intervention using the SPSRS application, which is a smartphone application. SPSRS is programmed to present 150 ms of positive words after presenting 17 ms of self-confidence-boosting words in videos.

These words are repeated every 5 s. The words to increase self-confidence are "can," "let us try," "good luck," "able," and "do not worry". These self-confidence-boosting words randomly appear in the four corners of the screen. The positive words are "nice," "great," "fantastic," "satisfactory," and "enjoyable". These words are displayed at the center of the screen. Interveners use the SPSRS application according to the operating manual. The participants will use an iPhone managed by interveners to watch a pre-determined 10-minute video.

The control group uses the same iPhone as the experimental group. The control group uses the YouTube application to receive video-viewing intervention. The control group videos do not show confidence-boosting and positive words. The control group watches the same video as the experimental group for 10 min.

The experimental group receives video-viewing intervention using the SPSRS application, which is a smartphone application. SPSRS is programmed to present 150 ms of positive words after presenting 17 ms of self-confidence-boosting words in videos.

These words are repeated every 5 s. The words to increase self-confidence are "can," "let us try," "good luck," "able," and "do not worry". These self-confidence-boosting words randomly appear in the four corners of the screen. The positive words are "nice," "great," "fantastic," "satisfactory," and "enjoyable". These words are displayed at the center of the screen. Interveners use the SPSRS application according to the operating manual. The participants will use an iPhone managed by interveners to watch a pre-determined 10-minute video.

The POMS 2-A Short is a 35-item self-administered questionnaire used to measure mood states. Items are rated using a 5-point Likert-type scale (0 = not at all, 1 = a little, 2 = moderately, 3 = quite a lot, and 4 = extremely). The POMS 2-A Short assesses seven domains, namely, anger-hostility, confusion-bewilderment, depression-dejection, fatigue-inertia, tension-anxiety, vigor-activity, and friendliness. High scores indicate better vigor-activity and friendliness are better but more severe symptoms of the five other domains. In addition, the Total Mood Disturbance (TMD) score is calculated from anger-hostility, confusion-bewilderment, depression-dejection, fatigue-inertia, tension-anxiety, and vigor-activity. TDM is calculated based on a standard value (mean of 50 and standard deviation of 10).

The STAI is a self-administered questionnaire consisting of two scales that each assesses state anxiety and trait anxiety. Each scale consists of 20 items. Items for STAI-S are scored using a 4-point Likert-type scale (1 = not at all, 2 = somewhat, 3 = moderately so, and 4 = very much so) with the total score ranging from 20 to 80 points. The higher the score, the greater the state anxiety.