In psychology, the theory of attachment can be applied to adult relationships including friendships, emotional affairs, adult romantic relationships or platonic relationships and in some cases relationships with inanimate objects ("transitional objects"). Attachment theory, initially studied in the 1960s and 1970s primarily in the context of children and parents, was extended to adult relationships in the late 1980s. Four main styles of attachment have been identified in adults: * secure * anxious-preoccupied * dismissive-avoidant * fearful-avoidant