There are some things you must never say on a first date. Such as: "Let's get married" or "have you always been fat?" or "prison isn't as bad as you think". And don't whatever you do, do what Louis did on the new series of First Dates (Channel 4, Thursday, 10pm) and open your date with the ultimate no-no, the definition of turn-offs, the phrase that will end your chances of getting lucky: "I am a Liberal Democrat."

To be honest, it wasn't the worst of Louis's problems, which was the fact that he had a chronic lack of confidence. It was like he was wearing his nerves on the outside of his skin, for all to see, quivering and crackling at the sight of a girl - and he knew where the problem started.

"When I was 13 years old at boarding school, there was a girl I liked," he said. "I wanted to find the courage to talk to her, but at the last minute I lost my nerve. And even though years have passed, you still become that 13-year-old boy who's quite scared and wanting to try to think of something witty and intelligent to say."

Louis did occasionally find something witty to say on his date – there was a good joke about Lib Dems and coalitions – but for the girl he was meeting, Adela, his lack of confidence was a problem. Everything else was fine, she said, but, however nice Louis was, she seemed to lay down a rule: a nervous man is not a sexy man.

This is a recurring pattern that, warm and friendly though it is, First Dates has rather exposed: women are not as good at dates at men. Far too many women, such as Adela, seem to sit back and expect to be amused or entertained or impressed rather than try very hard themselves, and, most astonishingly in an age when women are just as likely as men to be earning a wage, many still appear to expect the man to pick up the bill.

Many other women on the show turn up to dates with an invisible (because it's in their heads) list of the qualities that the man must possess, which rather dooms the date to failure before it even gets started. Anna was a good example. She told us she had been single for a long time, but seemed unable to see the obvious reason why, which was that she had a perfect man in her mind who, whenever she goes on a date, is always sitting there, invisible and impossible.

Anna listed the qualities this perfect man should have: he should be good looking, she said, and have nice shirts, and a good dress sense, and he must have a good pair of high-topped trainers, he must be ambitious and driven, flared trousers are a no-no, he must have flawless skin, good teeth, he can't be short and he must have nice fitting jeans – they can't be too loose. Why on earth would she do this to herself?

There are other similar patterns of behaviour that you see in First Dates over and over again, which is what makes the programme so interesting. The best thing about dating shows is not that couples get together and find love, which they occasionally do, it is that the programmes expose what not to do on a date – the mistakes that will keep you single.

But there is also another, more comforting element to First Dates. Over on the other channels, the news bulletins were telling us how horrible we all are to each other, but First Dates gets to the truth about human nature: most of us are nice, most of us get nervous, most of us try our best.