Cultural heterosexist ideologies assume heterosexuality to be the default norm. Four studies investigated when concepts of romantic love are heterosexual-by-default (N = 685). In Studies 1-2, participants generated features of romantic love, in general (i.e., the default prototype) or among one of three sexual orientation-specific couples (lesbian, gay, or heterosexual). Heterosexual-identified participants' default prototypes were more similar to heterosexual than same-gender prototypes (Study 1). Lesbian-and gay-identified participants' default prototypes were more similar to both heterosexual and gay male than lesbian prototypes, whereas bisexual-identified participants' sexual orientation-specific prototypes were equivalently similar to the default (Study 2). However, heterosexual-identified participants rated presented features of love similarly across sexual orientation-specific conditions (Study 3). In a timed feature-verification task (Study 4), participants categorized fewer peripheral features of romantic love as relevant to same-gender than mixed-gender couples. Activating sexual orientation-specific representations affected subsequent default concepts of romantic love. We discuss implications for heterosexism theories and intervention. A man and his son were away for a trip. They were driving along the highway when they had a terrible accident. The man was killed outright but the son was alive, although badly injured. The son was rushed to the hospital and was to have an emergency operation. On entering the operating theater, the surgeon looked at the boy, and said, 'I can't do this operation. This boy is my son.' When presented with this 'surgeon riddle,' only half of participants correctly guess that the surgeon is the boy's mother (Reynolds, Garnham, & Oakhill, 2006, see Hegarty, 2017, Studies 3-4 for recent replication). This classic riddle can confuse people, who automatically construct categories as being populated by prototypical members of those categories by default (Bodenhausen & Peery, 2009; Rosch, 1975). People often construct concepts in ways that assume certain characteristics (e.g., White, male, heterosexual) that go without saying (Bodenhausen & Peery, 2009; Hegarty, 2017). The surgeon riddle tricks readers who automatically construct a representation of 'the surgeon' as a man in the final This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.