4) Y-scale. To verify the concurrent validity of the first SAS, Y-scale was added, consisting of 20 items and scored based on a 5point scale measuring Internet addiction, which was demonstrated to have strong internal reliability [12,13]. As with the first SAS, the term ‘‘Internet’’ in Y-scale was changed to ‘‘smartphone.’’ In this study, the internal-consistency test result (Cronbach’s alpha) of Yscale was 0.95.