Individuals guess women’s and men’s sexual orientation on the basis of visual, non-verbal, and vocal cues. People use these cues as signs of others’ sexual orientation. Here, we review research showing how perceiving others’ sexual orientation depends on two assumptions. People assume first that all individuals are straight and a minority of people have a different orientation. Second, this assumption is adjusted by the perception of individuals' masculinity and femininity, such that men deemed more feminine are perceived as gay, while women deemed more masculine are perceived as lesbian.
These beliefs and exceptions are part of a larger belief system that is limited, in that it not only assumes a binary model of sexuality, but also may harm those whom gaydar depicts as gender non-conformers because of the assumption that people are heterosexual by default.