Women who identify as straight become aroused by naked videos of both sexes, a study by the University of Essex has found

As part of the study, women were shown videos of naked women and naked men.

Their responses, including whether their pupils dilated, were recorded. Researchers found 74% of women, who said they were only interested in men, were strongly aroused by both sexes.

Lesbian women were far more aroused by intimate clips of women and were barely stimulated by similar clips of men.

The researchers said lesbians were like men in their responses because men usually show distinct sexual responses to their favoured sex.

The study involved 345 women and was led by Dr Gerulf Rieger from the Department of Psychology.

On the results Dr Rieger said: ‘Even though the majority of women identify as straight, our research clearly demonstrates that when it comes to what turns them on, they are either bisexual or gay, but never straight.’

He also said his study showed that lesbians who dress in a masculine way did not necessarily have more masculine behaviours.

‘Although some lesbians were more masculine in their sexual arousal, and others were more masculine in their behaviours, there was no indication that these were the same women,’ he said.

‘This shows us that how women appear in public does not mean that we know anything about their sexual role preferences.’