Self-reported surveys in media usage behavior have been conducted by many companies and institutions. However, whether such surveys accurately reflect the actual usage has rarely been discussed. In this study, we revealed the difference between self-reported survey and automatically collected behavior log for smartphone usage duration, and investigated the relationship of individual attributes to the difference. Though past studies focused on measures (frequency versus duration) or question formats (open-ended versus closed), we successfully reduced the difference by adopting questioning methodologies, i.e., recall aids and timetable. We found that; (1) smartphone usage duration tends to be underreported, (2) when reported results highly deviate from the log, applying recall aids and timetable questionnaire reduces the difference, and (3) the difference is affected by age, gender, full-time job, and leisure time.
