WHEN it comes to maturity, men are the weaker sex. They act like schoolgirls and grow up only when they marry, say researchers.

Apparently, the average male aged between 20 and 29 has the same "mental

orientation" as a girl of 14 to 19. It is only when he reaches 30 that he becomes more mature and responsible in outlook - usually coinciding with marriage.

On the other hand, says the report by a business

consultancy, the mental

orientation of women changes gradually as they grow up and they become more sensible and less thrill-seeking.

I'm sorry, but I beg to

differ. As a fortysomething woman, my mental age is around 15 and has been ever since I was around 15. I have female friends too, in their thirties and forties who haven't progressed beyond the giggly fifth-former stage.

It's not something I'm proud of. At school I had the attention span of a dust mite and always found it hard to sit quietly in the classroom. I would get into trouble over and over again for tying

people's coats to the backs of their chairs, passing notes or - on one occasion - filling my slide-rule case with water and firing it at people through an empty ball-point pen.

I'm not quite that bad now, but that's not because I don't feel inclined to do things like that. My last job involved

sitting for hours in some very tedious meetings with a bunch of academics. My female colleague and I would pass messages to each other, about how much we'd have to be paid to do certain things with the most unappealing among them. Like a couple of children, we would put our hands in front of our faces and almost choke with laughter.

Recently, at a

neighbourhood watch meeting, my friend and I acted along similar lines when a couple of firemen stopped by.

It's really hard to act

sensibly when your mind is telling you to be anything but. It's even harder when you become a parent.

I can't set foot in my

daughter's school without saying or doing something ridiculous and embarrassing myself in front of the very mature and proper parental masses.

It's crazy, but I can't shake the feeling that one day I'm going to be pulled to one side and asked to stand outside the headmaster's office.

People say act your age, but what is that supposed to mean? Do we have to act in a certain way to be accepted in polite society?

I really envy TV comics who, despite being

fortysomething, can act

ridiculously and not be seen as needing medical help.

As for men - well, my

husband is far more sensible than I am. For as long as I can remember, he has frowned upon my behaviour, even more so than that of the children. On visits to the art gallery, he tells me to be quiet - "If you can't stop

making stupid comments, then don't walk round with me," he says.

He goes mad when I make cakes and coat the kitchen with flour and when I owned a bike he would give me a severe ticking-off for riding on the pavement.

While I hanker after nights out with the girls (not that they ever happen), his idea of thrill-seeking is to have an extra biscuit after a meal.

You couldn't get more of a contrast. I act like a teenager and he acts like a staid, pipe and slippers pensioner.

I keep telling him that he'll have to get used to it, because his problems are only just beginning. In a few years, he will be surrounded by women with the mental age of teenagers.

My two daughters will actually be teenagers, the other will be in her early fifties.