They say you should never judge a book by its cover.

But when it comes to the opposite sex, it seems that's exactly what women do.

It takes a woman just three minutes to make up her mind about whether she likes a man or not, a study has revealed.

The average female spends the time sizing up looks, physique and dress-sense as well as taking in scent, accent and eloquence of a potential suitor.

Women also quickly judge how he interacts with her friends and whether he is successful or ambitious.

It also emerged most women believe 180 seconds is long enough to gauge whether or not he is Mr Right, or Mr Wrong.

The study also found women rarely change their mind about a man after their initial reaction — and believe they are "always right" in their assumptions and judgments.

The report which was commissioned among 3,000 adults to mark the release of Instinct, a new book by Ben Kay.

Kay said: "I think a lot of people believe in trusting their instincts when dating. It makes it seem more magical, like it's coming from somewhere deeper."

"But it's surprising how quickly women make a decision. That's barely enough time to finish a drink together."

"It's interesting that so many women trust their instincts and yet still give men the opportunity to change their minds."

"Some men might think this is leading them on but I would imagine most women just want to give every bloke a fair shot."

Researchers found women will quickly dismiss a man who they feel is "too cocky" or "too needy".

He will also be rejected if he isn't nice to people, doesn't appear to earn enough and if he has nothing in common with the woman.