According to the cultural anthropologist Gayle Rubin, heteronormativity ranks sexual practices from "good sex" to "bad sex." This "sex hierarchy" ranks sex between two married heterosexual people for the purpose of creating a child as "good," and ranks people and acts that fall short of this standard lower until they become "bad sex." Gay couples who are married are somewhere in the middle. Gay people who have sex with many partners are also in the middle, but below gay married couples. Patrick McCreery, a lecturer at New York University, believes this is the reason why gay people are attacked for doing things that straight people also do, such as watching pornography or practicing BDSM.