The purpose of this study is to elucidate what the self-report scales of “smartphone addiction” truly reflect by analyzing whether they are better explained by users' self-perception of usage or by actual usage log data.

In this study, we combined five months of app launch log data from 602 Android smartphone users who had given prior consent, with survey data in which participants reported their selfperception of usage for key apps. The analysis was conducted using Structural Equation Modeling (SEM) to examine the relationship between “smartphone addiction” and these variables. The results showed that the actual frequency of app launches, as recorded in the log data, had little correlation with “smartphone addiction”, while the self-reported perceptions of app usage were significantly related. Additionally, it was found that users with consistently high weekly smartphone usage patterns exhibited significantly higher tendencies toward addiction compared to those with lower usage patterns.

These findings suggest that “smartphone addiction”, as measured by self-report scales, primarily reflects users' subjective perceptions of their usage rather than simply indicating excessive use based on objective launch log data, thereby capturing a different dimension of behavior.

This paper discusses the history of the unification of the Japanese input methods. To this end, the paper conducts a literature review, focusing on input devices—including non-existent ones —developed between 1979 and 1983, five years after the introduction of Japanese word processors. The research reveals that after initial branching, hardware that used the kana-kanji conversion eventually consolidated into a unified system. It further highlights the diversity in the ease of use, difficulty, and “efficiency” of input, depending on the user's skills. Unlike the prevalence of touch typing in Western countries, Japanese users tend to look at their hands while typing. In this case, the ease of retrieval is emphasized, with knowledge of the Japanese syllabary (gojūon) acting as an index. While touch typing might be the ultimate form of “efficiency,” using knowledge of the Japanese syllabary (gojūon) to locate letters quickly offers another strategy to improve “efficiency” for those less skilled at touch typing. Therefore, Romaji input, which separates vowels and consonants and uses fewer characters than kana input, was adopted. The experience of using a word processor in the 1980s helped smooth the transition to typing on mobile devices in later years.