“Love is blind” is the well known phrase, and now it officially also makes you stupid, according to new research.

Professor Robin Dunbar, an evolutionary psychologist from the University of Oxford, argues that the rational parts of the human brain shut down when experiencing the feelings of love, The London Times reported.

His theory comes after analysing the findings of brain experiments through the UK over a decade ago at the University College of London.

The magnetic resonance imaging (MRI) research team looked into the brain activity of seventeen volunteers as they were shown pictures of their boyfriends and girlfriends, and other close loved ones.

The professor says that when the people gazed at images of their loved ones, the rational parts of their brain were affected by “rose-tinted spectacle syndrome” and their hearts ruled their heads, dulling their critical faculties.

“What seems to be happening is that you have subconsciously made up your mind that you are interested in the person and the rational bit of the brain – the bit that would normally say ‘hang on a minute’ – gets switched off,” Professor Dunbar explained at The Times Cheltenham Science Festival.

“In a relationship you are in a trade-off between caution and just going for it. There is a view that emotion exists to get you off the fence.

“A purely rational organism would sit on the fence all the time to avoid being hurt. But if you don’t engage, you won’t form relationships. If the prefrontal cortex is shut down, that protective and cautious element goes.”

So, last weekend when you bought her and all her friends drinks, that was your love drive kicking in!