While most previous work on what turns people on has involved measuring their genital responses, Gerulf Rieger, a researcher at Cornell, said measuring dilation or widening of the pupil in the eye can achieve the same goal, HealthDay reports. In fact, Rieger suggested in a paper published in the journal PloS One that data gathered from studying eye response might be more sensitive.
For example, Rieger said, straight men respond to sexual videos of women and not of men, while women respond to videos of both genders. Previous research has suggested women have a somewhat different sexual response than men.
But the team also found a range of responses in men who identify as mostly straight and those who say they are bisexual. Researchers had believed bisexual men's identity was not rooted in their sexual response, but the team found this is untrue.
"We can now finally argue that a flexible sexual desire is not simply restricted to women -- some men have it, too, and it is reflected in their pupils," Ritch Savin-Williams, a professor in human development and co-author of the paper, said. "In fact, not even a division into 'straight,' 'bi,' and 'gay' tells the full story. Men who identity as 'mostly straight' really exist both in their identity and their pupil response; they are more aroused to males than straight men, but much less so than both bisexual and gay men."