Parental acceptance-rejection theory (PARTheory) is a theory of socialization that attempts to predict and explain worldwide causes, consequences, and other correlates of parental acceptance-rejection. Additionally, the theory attempts to predict and explain the consequences of acceptance-rejection in other primary interpersonal relationships, including intimate adult relationships. Empirical evidence overwhelmingly supports the major postulates of the theory, especially PARTheory's personality subtheory which predicts that perceived parental rejection is likely to be universally associated with a specific form of psychological maladjustment. Members of every society and ethnic group so far studied tend to respond to perceived acceptance-rejection precisely the way the theory predicts. With this information it should now be possible to formulate culture-fair policies, programs, interventions, and other applications for enhancing the welfare of humans elsewhere.