This study aimed to identify kindergartener intra-individual variables related to smartphone overuse. Based on
previous findings in the addiction literature and related theoretical explanations, this study focused on kindergartener
gender, age at the time of first smartphone use, smartphone proficiency, four temperaments (novelty seeking, harm
avoidance, reward dependency, persistence), and length of time using the smartphone for three different purposes
(weekly smartphone use for learning, for streaming, and for gaming) and examined the relationships between these
variables and kindergarteners’ smartphone overuse scores. For this purpose, the study asked mothers of 5-year-old
children in Seoul and Gyunggi areas to complete questionnaires. A total of 234 mother-reported data pertaining to 97
boys (41.5%) and 137 girls (58.5%) entered into analyses. All the kindergarteners analyzed were reported to have
experiences using the smartphone. Correlation analyses demonstrated smartphone overuse to be correlated positively with
novelty seeking, smartphone use for gaming and for streaming, smartphone proficiency, harm avoidance and reward
dependence, and negatively with persistence and age of first smartphone use. Stepwise multiple regression analysis
found that 6 (novelty seeking, smartphone use for gaming, smartphone proficiency, smartphone use for streaming, harm
avoidance, and age of first smartphone use) out of a total of 10 kindergartener variables significantly predicted
kindergartener smartphone overuse scores. Clinical implications of these research findings and recommendations for
future study were discussed.