Psychologist David J. Ley wrote that that the popularity of transgender porn may have various causes, including sexual fluidity, the novelty factor, and because some trans women may act more like men sexually.[31] Author J. Phillips wrote that the "phallic woman...challenges the fixity of our own sexual identity."[32] Neuroscientist Ogi Ogas said that some straight men are interested in porn with trans women because the brain likes "different sexual cues in novel combinations" and that men seem to have a strong interest in penises regardless of sexual orientation.[33]