A 2016 study that used the penile plethysmograph demonstrated that the arousal patterns, genital and subjective, of men who report attraction to transgender women who have "female-typical physical characteristics (e.g. breasts) while retaining a penis" are similar to those of straight men and different from those of gay men. The study showed that these men are much more aroused to female than to male stimuli. They differed from both the groups of straight and gay men, however, in also displaying strong arousal to stimuli featuring trans women, to which they responded as much as to the cisgender female stimuli. The study also found that autogynephilia is common in this group: 42% of the study group reported experiencing autogynephilic arousal, whereas only 12% of straight men and 0% of gay men did. Of the men attracted to trans women, 41.7% identified as bisexual, with the remainder identifying as straight. The bisexuals among them did not display significantly more arousal to male stimuli than their heterosexual counterparts, however. They did report a higher number of male sex partners, and they had higher levels of self-reported autogynephilic arousal than their straight counterparts.