MRI brain scans show heterosexual women just as likely to be aroused by erotic material featuring men as material featuring women Kyoto University

Heterosexual women are just as likely to be aroused by erotic material featuring men as material featuring women, according to a new study published in the journal Scientific Reports.

The research, which used neuro-imaging to measure brain activity in a region responsible for pleasure and reward, also showed that gay and straight women had different responses to sexually arousing stimuli, although there was little difference between the responses of straight and bisexual women.

"Our interest in this topic came from previous research looking at physiological measures of sexual arousal," study author Adam Safron from Northwestern University, told PsyPost. "Surprisingly, women have tended to show substantial arousal to both male and female sexual stimuli, regardless of which sex they prefer."

For the study, researchers examined the brain activity of 26 heterosexual, 26 bisexual and 24 homosexual women while they viewed erotic material – which included pictures of naked men and women, lesbian or gay couples sexually interacting and videos of both men and women masturbating.

They found that both bisexual and heterosexual women tended to show similar degrees of arousal to erotic stimuli depicting either sex. This stands in contrast to men whose brain activity corresponds with their sexual orientation, according to the psychological literature.

In a previous study conduced by Safron and colleagues, heterosexual men were observed responding more strongly to erotic images of women, while gay men responded more strongly to material showing men.

The researchers acknowledge some limitations in their study. For example, it is difficult to determine whether activity in the brain's reward system directly reflects real sexual desire.