Gender identity refers to a person's basic sense of self as a male, a female, or some other "third" type of gendered subjectivity. By the age of 3, most children demonstrate the rudimentary capacity to self-label their gender identity. Thus, most preschoolers can answer "correctly" the basic question "Are you a boy or a girl?" However, most preschoolers do not appreciate that gender is an invariant aspect of the self. Thus, 3-year-olds may not understand that they will grow up to be a man or a woman, or they may believe that if they engage in cross-gender surface behaviors this will alter their gender. It is not until a few years later that children appear to master the concept of gender constancy (Zucker et al. 1999). Children also attach affective meaning to being a boy or a girl. There is, for example, a tendency among young children to "overvalue" their own gender and "devalue" the other gender, a phenomenon that developmental and social psychologists have studied under the rubric of "in-group" and "out-group" biases (Susskind and Hodges 2007).