Gay? Check the Pupils

Scientists have a new way of investigating a subject's sexuality: It's all in the eyes, they say. Instead of using invasive methods—such as a band around the penis—to determine sexual response, researchers at Cornell simply measured the dilation of subjects' pupils in response to erotic videos, using an infrared lens. The scientists say it could be the most accurate way of determining a person's sexuality, the Los Angeles Times reports.

"We wanted to really find a measure of sexuality that goes beyond what people tell us," says one of the researchers. In the study, scientists found that both heterosexual men and homosexual women largely responded to erotic videos of women. Heterosexual women, however, responded to videos of both sexes. "That doesn't mean they are bisexual," a researcher tells ABC News. Instead, it's likely a "protective" response evolved in reaction to the threat of rape, the researchers say. (More eyes stories.)