Gender expression, or gender presentation, is a person's behavior, mannerisms, interests, and appearance that are socially associated with gender, namely femininity or masculinity. This includes gender roles, and accordingly relies on cultural stereotypes about gender. Terminology Gender expression typically reflects a person's gender identity (their internal sense of their own gender), but this is not always the case. Gender expression is separate and independent both from sexual orientation and sex assigned at birth. Gender identity can be expressed through behavior, clothing, hair, makeup and other aspects of one’s external appearance. Gender expression does not always fall in line with a person's gender identity. A type of gender expression that is considered atypical for a person's externally perceived gender may be described as gender non-conforming. In men and boys, typical or masculine gender expression is often described as manly, while atypical or feminine expression is known as effeminate. In girls and young women, atypically masculine expression is called tomboyish. In lesbian and queer women, masculine and feminine expressions are known as butch and femme respectively. A mixture of typical and atypical expression may be described as androgynous. A type of expression that is perceived as neither typically feminine or masculine can be described as gender-neutral or undifferentiated. The term gender expression is used in the Yogyakarta Principles, which concern the application of international human rights law in relation to sexual orientation, gender identity, gender expression, and sex characteristics. The term also designates a criterion for human rights protection in certain countries, including Canada. Confusion between gender expression and sexual orientation While gender expression does not necessarily connect to sexuality, individuals often are misinterpreted as more masculine if lesbian and more feminine if gay, regardless of the individual's gender expression. These beliefs can lead to people misinterpreting an individual's gender expression based on their sexuality. Studies on adolescents conducted by Stacey Horn, showed that gay and lesbian individuals who did not express themselves as their assigned gender were seen as less acceptable. Individuals who expressed themselves with their assigned gender typically faced less social harassment and discrimination. On the other hand, heterosexual males whose gender expression was more feminine than masculine were the most discriminated against. "The heterosexual matrix" theory created by gender theorist Judith Butler posits that people often assume someone's sexuality based on their visible gender and sex. Lisa Disch states that it explains why people tend to assume someone's