A new study has claimed to have found a way to tell whether someone is straight, gay or bisexual.
According to Live Science, scientists believe pupil dilation is an accurate way of discovering a person’s sexual orientation.
When people look at erotic images and become aroused, their pupils open up in an unconscious reaction that could be used to study orientation and arousal.
According to study researcher Ritch Salvin-Williams, a development psychologist at Cornell University in New York, it is the first large-scale experiment of this kind.
Savin-Williams said: ‘So if a man says he’s straight, his eyes are dilating towards women.
‘And the opposite with gay men, their eyes are dilating to men.’
Savin-Williams and colleague Gerulf Riegar turned their eyes onto the students of the university, recruiting 325 gay, straight and bisexual men and women for the test.
The volunteers’ eyes were filmed as they watched separate one minute videos of a man masturbating, a woman masturbating and neutral landscape scenes. Students also reported on their own arousal after the test.
The videos were matched for brightness so that differences in light would not skew the results.
Results showed pupil dilation matched the pattern seen in genital arousal studies.
In men, the pattern is straightforward: straight men respond to sexual images of women, gay men like men, and bisexuals respond to both men and women.
Savin-Williams said with women, it was more complex.
Gay women show pupil dilation to images of other women, similar to straight men. But straight women dilate equally in response to erotic images of both sexes, despite reporting feelings of arousal for men and not women.
This doesn't mean that all straight women are secretly bisexual, Savin-Williams warned, just that their subjective arousal doesn't necessarily match their body's arousal.
He suggested a theory that because women have been raped throughout history, their genitals are more likely to lubricate from any sexual stimuli as a way to ensure their genes can still be passed on.
UK-based Pink Therapy’s Dominic Davies disagreed with this theory. He told Gay Star News: ‘I think it's more that women are more relational than men and enjoy seeing people (of all genders) having a good time.’
The American psychologist also said our pupils dilate slightly in response to any interesting stimulus, such as a beautiful piece of art.
Davies said pupil enlargement really tells us whether we find what we are looking at is attractive, but studies like this should not be a threat to us.
‘I find it relatively unremarkable and unsurprising,’ he said. ‘I think most people are kind of ‘so what’ about determining sexuality – especially now that it’s known to be a lot more fluid for a lot more people!’
Although Savin-Williams said the test was infallible, he said some people do not have genital responses in a laboratory environment.
‘Some people just don't want to be involved in research that involves their genitals,’ Savin-Williams said.
The researcher said he hoped the technology would be used to study sexuality worldwide, and help confused patients to discover their true sexual orientation.