Watching porn reduces brain activity in the area responsible for visual stimulation — a finding which has scientists perplexed.

Perhaps unsurprisingly, instead of activating the visual area of the brain, our bodies send more blood to other parts. But that's not what scientists are most interested in. Rather, they've found that our brains might not need to watch the full extent of a sex scene.

According to study researcher Gert Holstege, while the details in straight-laced films are important in order to follow the plot, the same does not apply to a sex scene because we know exactly what comes next, meaning that we are able to switch off any distracting brain activity like the visual part of our brain.

Scanning the brain activity of 12 women during a simple nature documentary and two women-friendly erotic films (one in which only manual stimulation and oral sex took place, the other which contained vaginal intercourse), Holstege and his team found that brain activity in the primary visual cortex was reduced for the women only during the second more intense erotic film.

Holstege explains that this drastic reduction in visual activity within the brain is part of the brain's way of preserving energy. In this case, the brain effectively prioritises sexual arousal over visual stimuli.

This may be due to an evolutionary factor that Holstege notes in an argument around anxiety versus arousal. When you're feeling anxious, the brain is not able to switch on arousal because only one of the two reactions can occur at one time, a point which Holstege says might help to explain sexual dysfunction - why women who have high levels of anxiety very often also have low levels of sexual desire.

"If you yourself are in a very dangerous situation, whatever the reason, you don't have sexual feelings, because you have to survive for yourself, not survive for the species," he told LiveScience.

The bottomline? Ensuring that your partner feels they are in a safe environment will help reduce anxiety and improve sexual arousal.