Gender performativity is a term first used by the feminist philosopher Judith Butler in her 1990 book "Gender Trouble". She argues that being born male or female does not determine behavior. Instead, people learn to behave in particular ways to fit into society. The idea of gender is an act, or performance. This act is the way a person walks, talks, dresses, and behaves. She calls this acting "gender performativity." What society regards as a person's gender is just a performance made to please social expectations and not a true expression of the person's 'gender identity'.