Lesbians kissing in South Africa, where same-sex marriage is legal (Photo by RAJESH JANTILAL/AFP/Getty Images)

A study has determined that no one is 100 percent heterosexual.

Researchers studied the reaction of men and women who identified as heterosexual when they were shown different kinds of pornographic material.

Primarily, the measured the dilation of pupils in response to the material.

It found that straight-identifying women’s eyes dilated when they looked at erotic material that involved both a man and a woman and two women.

The author of the study, Ritch C Savin-Williams explained that the point of the study was to show that people are “not either gay, straight, or bi.”

He explained that it proved that sexuality is a “continuum” and that he hopes it will help clear up a lot of misconceptions and stigma about bisexual people, in particular about bisexual men.

Related: Straight men watch gay porn a quarter of the time, study reveals

“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,” Savin-Williams said.

The researcher explained that he is not “surprised” by the research findings, however, he was shocked at how many people are still identifying as heterosexual despite the obvious attraction that exists between people of the same sex.

“We’re trying to get at the way people really are,” he said. “Sometimes, it seems people are one way but believe they have to report themselves in another way, and that’s not good.”

Savin-Williams added that the findings of the study proved a “loosening of the boundaries”.

“I think that’s happening for both sexes. It’s probably a good thing, because it gives kids growing up more diversity, more options, so they don’t feel like they have to fit in [at all costs].

“Straight women and straight men feel much more comfortable than ever before in going into the realm of the other sex in terms of gender role and how they act.”

Related: One in three Americans think that being transgender is a sin, study reveals

He added that by creating a space where people could be more accepting and welcoming of their sexuality then it would increase the self-esteem.

“Maybe they feel like they have more freedom [to be who they really are]. Granted, society may not always like it, but it is your own authentic self,” he concluded.