To assess young people's attachment hierarchy, the Important People Interview (IPI) was developed based on Bowlby's conceptualization of ethological behavioral systems. The present study examined the validity of the IPI in a sample of Japanese young adults (N = 472; Mage = 20.34, SD = 1.28; females = 53.81%), because Bowlby's behavioral systems conceptualization has been assumed to be universal. Confirmatory factor analyses revealed agood fit of the IPI model with a Japanese sample. The ranking of the mother in attachment hierarchy correlated positively with young adults' self-esteem, and the ranking of the father correlated negatively with their depressive symptoms. The absence of romantic partner; shorter romantic relationships; living separately with mother, father, and romantic partner; and less frequent meetings with the mother, father, and romantic partner correlated with the higher ranking of friends. When other attachment figures are unavailable, people may flexibly use friends to meet their attachment needs.
Keywords: Attachment hierarchy; Japanese culture; behavioral systems; friendship; important people interview.