Men and women think differently about cars and driving. In today’s atmosphere of equality it may seem slightly unfashionable to admit that you believe in mental gender differences, but I’ve studied communication between the sexes for more than 30 years and I know that huge misunderstandings arise when we fail to take our basic differences seriously.

To start with the obvious, men and women often have a different taste in cars. Typically men will go for more speed and larger engine size while women are attracted by space and storage. I have a great analogy to help understand this. Men usually only carry a wallet, which is just for essentials, whereas women carry handbags stuffed with everyday useful items.

The basic formula on Mars is “only carry what you have to carry, only do what you have to do”, which is a formula for efficiency. Whereas on Venus women like to have everything they could possibly need.

This is not to say a man can’t impress a woman by his choice of car. Women are impressed by a man’s car but it’s not the engine size that attracts them. It’s more likely to be the cost of the car — an expensive one tells her he is successful.

Equally important is how he looks after his car. A woman will look at the car’s cleanliness, which tells her he is capable of taking care of her. If a man is clearly proud of the things that he has and takes good care of his car then, she reasons, if she becomes a part of his life he’ll take care of her too. The flipside of all this is that the kind of car a woman drives doesn’t have much effect on a man.

What does have an effect on a man is how the woman acts when she is in the car with him — particularly when it comes to speed. One of the aspects I explored in my recent book, The Mars & Venus Diet and Exercise Solution (www.marsvenussupershake.com), is that men’s testosterone levels tend to be 10-20 times higher than a woman’s.

A man needs to make a lot more testosterone during the day to keep stress levels down, and driving faster makes him feel better for this reason. Danger produces more dopamine in the brain and it stimulates testosterone, which lowers the stress hormone cortisol, so it’s pleasurable for a man to drive fast.

But this can create a huge conflict between the sexes whenever they are on a journey together. A woman may start to feel unsafe at high speeds and will start giving her man driving instructions (and men always take driving instructions as criticism).

The mistake women make is to start using rationalisations to justify their discomfort. These insinuate that the man is a bad driver: “You could get a speeding ticket”, “What if we have an accident?”, “You’re cutting that person up”.

She’s only expressing her feelings, but when he’s driving that kind of talk sounds like criticism to him and he will react defensively.

Often couples will decide that as a solution to this problem she should drive whenever they are together. He’ll say: “Look, I’m tired of your complaining, you drive.”

But it’s a bad move for men to abdicate like that — sharing the driving is not a bad thing, but when the woman will not be driven by her husband she’s affirming the fact that she doesn’t trust him and he’ll feel the criticism with her every turn of the wheel. He’ll go kind of numb, telling himself that he’s getting a bargain because he can just sit and relax. But it doesn’t empower him and it does nothing to lower his stress.

Passion in a marriage can be killed when a woman gives too many driving instructions to a man. And when women are driving men around all the time you can bet that couple are not having much sex any more — that behaviour doesn’t foster increasing testosterone, which is part of the attraction between a man and a woman.