In the study, bisexual men reported being sexually aroused by erotic videos of both men and women. But a device attached to their genitals told another story.
Gerulf Rieger, a PhD candidate at Northwestern University, conducted the study with psychology professor J. Michael Bailey, PhD.
"We used measures of sexual arousal to explain true sexual feeling," Rieger tells WebMD. "In men, there is no good evidence that something like a true bisexual attraction is out there."
That conclusion doesn't fit with the experience of San Francisco psychologist Geri Weitzman, PhD, who runs a Web site listing bisexual-friendly professional services.
"I have seen in my practice very, very, very many men who are bisexual," Weitzman tells WebMD. "Really, there are so many bisexual men out there. There are so many men who say — and demonstrate — that they love men and love women and are happy with it."
Rieger and Bailey are looking in the wrong place for men's sexual identities, says Sheeri Kritzer, a Bisexual Resource Center board member. Identity, she says, comes from above the ears, not below the belt.
"The whole point of sexual identity is it is a validation of who you are," Kritzer tells WebMD. "This study perpetuates the idea that men are studs, that they go with whatever turns them on. It goes on the old stereotype that men think with their [penises]."
Sexologist Paula Rodriguez Rust, PhD, is the editor of the 1999 book "Bisexuality in the United States." She says a person's sexual orientation is not determined merely by genital arousal.
"Sexual response is not everything we think of when we think of sexual orientation," Rodriguez Rust tells WebMD. "Bisexuality clearly exists."
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Bailey's sexuality research tends to draw fire. His 2003 book on transsexual men, "The Man Who Would Be Queen," is still under attack from some in the transgendered community.
Last year, Bailey, Rieger, and others published a study in which they measured female sexual arousal. They concluded that women — whether they identify themselves as homosexual or heterosexual — have bisexual arousal patterns. That's because the genitals of women participating in the study became aroused when they watched porn, regardless of whether it featured men or women.