Your girlfriend is probably turned on by other women—at least that’s what the findings from a new study in the Journal of Personality and Social Psychology suggest.In the experiment, women who claimed to be straight actually showed the same signs of physical arousal when watching sexy videos of naked women as they did when viewing ones of dudes. Blood flow to their genitals increased and their pupils dilated.
This shows that straight women may have a more fluid sexuality, meaning they could be turned on by men and women, says study author Gerulf Rieger, Ph.D., a psychologist at the University of EssexMen, on the other hand, tend to be less flexible with what turns them on.“We have conducted several studies on men, and the majority of straight men are almost exclusively sexually aroused by women,” he adds. “In general, the direction a man’s penis takes is a reliable indicator of his sexual orientation.”

Now, that’s not to say that all women definitely get turned on when faced with another scantily-clad female. Arousal is very individualized, and what turns on one woman may not necessarily rev up another.

Plus, even if the thought of other chicks does turn her on, she may never want to have a ménage a trois.

“Sexual arousal may happen automatically or subconsciously,” he says. “A sexual or romantic relationship with another woman may not be what she actually wants to pursue.”

So how do you know for sure? Gauge her interest by asking if she’d be into watching girl-on-girl porn with you. If she’s game—and she enjoys it—you can then bring up the idea of a threesome in a comfortable place, like her apartment or your home.