A new study suggests human sexuality is more fluid than previously thought, and even that nobody is fully heterosexual.

The research by Cornell University in the US assessed sexual orientation by measuring physical responses to porn, Gay Star News has reported.

“It’s a study that assesses sexual orientation by looking at the eyes and whether they dilate or not,” said researcher Ritch Savin-Williams.

“You can’t control your eye dilation. Essentially, that’s what the whole project attempts to get at, another way of assessing sexuality without relying on self report.

“Another way is genital arousal, but that gets a little invasive.”

The study found that straight men responded to seeing porn images of men, as well as images of women.

“We show straight men a picture of a woman masturbating and they respond just like a straight guy, but then you also show them a guy masturbating and their eyes dilate a little bit,’ said Savin-Williams.

“So we’re actually able to show physiologically that all guys are not either gay, straight, or bi.

“There are aspects [of male sexuality] along a continuum, just as we have always recognised with women.

“Men have gotten so much cultural crap put on them that even if a man does have some sexual attraction to guys, they would never say it.”

If all men are not quite straight, it could be good news—other research by Deakin University has found that bisexual men are better lovers to their female partners.

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