When the term “ambivalence” first appeared in 1910, it referred to a psychotic symptom of schizophrenia. Migrating into popular psychology, the condition soon became a neurosis associated with young women and homosexuals. By the late 1920s, “ambivalence” also described an aesthetic value associated with masculine intelligence. Extending recent work in new modernist studies, cognitive disability studies, and the social history of medicine, this essay traces the gendered contradictions of this psychosocial history. Historicizing ambivalence illuminates two distinct but interrelated concepts: ambivalence proper as condition of modern femininity and modernist irony as a masculinized expression of the same set of feelings and conflicts. Edith Wharton’s Twilight Sleep (1927) and F. Scott Fitzgerald’s Tender Is the Night (1934) reflect this interplay of psychic and aesthetic patterns, highlight the essential ambivalence of modern subjectivity, denaturalize contemporaneous scientific attitudes, and unsettle enduring critical assumptions about the interwar period’s literary forms.