SignificanceBiologists and social scientists have long tried to understand why some societies have more fluid and open interpersonal relationships—differences in relational mobility—and how those differences influence individual behaviors. We measure relational mobility in 39 societies and find that relationships are more stable and hard to form in east Asia, North Africa, and the Middle East, while they are more fluid in the West and Latin America. Results show that relationally mobile cultures tend to have higher interpersonal trust and intimacy. Exploring potential causes, we find greater environmental threats (like disease and warfare) and sedentary farming are associated with lower relational mobility. Our society-level index of relational mobility for 39 societies is a resource for future studies.

The author examined whether the level of self-disclosure would differ across four types of relationships--passionate love relationships, companionate love relationships, same-sex friendships, and cross-sex friendships--and across cultures: American culture and Japanese culture. Participants were 145 college students (64 Americans and 81 Japanese). The results supported three hypotheses: (a) Japanese students scored lower in self-disclosure than American students, regardless of relationship types, (b) self-disclosure was higher in same-sex friendships than in cross-sex friendships both among American participants and among Japanese participants, and (c) self-disclosure was higher in romantic relationships than in friendships both among American students and among Japanese students. However, the correlation between self-disclosure and passionate love was not stronger than the correlation between self-disclosure and companionate love. The author discussed the present study's findings and contribution.

This article reviews how behaviors and psychological tendencies in close relationships differ between cultures, and proposes a socioecological framework to understand those differences. Our review of the literature finds that paradoxically, people in individualistic cultures are more actively engaged in close relationships (e.g., higher levels of social support, self-disclosure, intimacy, and love) than those in collectivistic cultures. From an adaptationist perspective, we argue that one reason for these differences is higher levels of relational mobility in individualistic cultures. In societies with high relational mobility, where relationships are relatively more fragile, more active engagement in close relationships helps individuals to impress potential, and retain current, partners. We emphasize the importance of examining socioecologies to better understand close relationships.The field of relationship research as a whole has experienced dramatic progress over the last four decades, incorporating increasingly thorough examinations of interpersonal behaviors and psychological processes in close relationships, 1 including romantic relationships, friendships, and family relationships (e.g.,

According to the attraction–similarity model, relationship quality leads to perceptions of partner–self similarity. Relationship quality and perceived similarity then provide psychological benefits for the perceiver. Across 3 studies, relationship quality positively predicted perceptions of similarity. Study 1 indicated that for moderate, but not low, relationship‐relevant traits, individuals projected the self onto the dating partner as a way of perceiving similarities. In Study 2, priming high, as opposed to low, relationship quality led to greater perceived similarity on the moderately relevant traits. Study 3 indicated greater perceived similarity between self and dating partner than between self and average same‐gender student on the moderately relevant traits. Relationship quality and perceived similarity with the dating partner on the moderately relevant traits also predicted psychological benefits.

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