It's Christmas – the season for making merry, going out and, if you're single, trying to snog people under the mistletoe before the pubs close. So I thought it would be a good time to look at one of the oldest assumptions in the Men vs Women book: can women get sex whenever they want, while men are doomed to wait on the sidelines until our sexual fancy falls upon them?

I don't like the bar example. First, and most obviously, it is not universally true. There are women (and I am one of them) who have walked up to guys in bars, asked them for sex, and been flat-out refused. Likewise I've known men who have been able to get quick and easy sex with very little effort.

Second, not only does the bar example prop up unhelpful stereotypes about men (that they always want sex, because biology and testosterone and grrr), it also drives a hammer-blow into the self-esteem of any woman who has been turned down for a casual shag. Claiming that women can get sex just by clicking their fingers sets horny women up for a lifetime of disappointment, and gives men a reputation they can never possibly live up to.

But science says so!

If you're into odd sexual studies, like me, you'll probably be thinking of the Russell Clark experiment. In 1978, at Florida State University, students directed by Clark (a social psychology professor), approached people of the opposite sex at random and all asked the same question:

"I have been noticing you around campus. I find you to be attractive. Would you go to bed with me tonight?"

Not one of the women approached said "yes" to this proposition, but 75% of the men did. Assuming that men aren't simply aroused by awkwardly worded sentences, let's see why this might be the case.

Clark believed there was an evolutionary reason: women had evolved to be more selective about their partners than men. He backs this up by pointing to another part of the experiment (which, curiously, is much less commonly cited) that when the proposition changed to "would you like to go out with me tonight?" men and women accepted the proposition in roughly equal proportions. Others have suggested that it's about socially learned behaviour: women are taught not to look too "easy". Yet others have suggested that it's more about risk aversion: saying "yes" to a horny stranger opens women up to potential dangers.

I suspect we're affected by a combination of those factors, but that doesn't matter for this discussion, because I'm going to take the conclusions of the experiment as read: women will have a greater hit rate than men if they approach strangers and ask them for sex.

Is all sex the same?

So – happy ever after, then? Presumably I, and all the rest of the women, can now simply pick and choose whom we want to have sex with and – with little to no effort on our part – entice them into bed, orgasm ourselves rigid, and frolick forever in our sexual Utopia? Well no, obviously. It almost goes without saying that people want different kinds of sex. You might like giving head, whereas I'd prefer it if you gave me a hand job. I might like it rough and quick, while my friend wants to make much more gentle love. The fact that we all differ in preferences is obvious if you've watched any porn, read a book, or seen any human interaction ever.

Although the bar example seems to show women in a very privileged and powerful position – the ones who hold the keys to the sexual kingdom, if you like – what is actually on offer is a very limited type of sex: casual, quick, no-strings-attached sex with a stranger. This is problematic, because even if we accept the "women can easily get sex" proposition as true, we're not saying that women can fulfil their sexual needs easily, only that women can have this specific type of sex easily.

I'm happy to admit that women might be less inclined (although not universally disinclined – there are plenty of us on Craiglist too) towards casual sex with strangers, for one or all of the reasons stated above. But that doesn't mean that men necessarily have stronger sexual desire. It's possible that all the women approached in the bar are horny, or would love a shag, they just wouldn't want the kind of shag they'd imagine is on offer when a total stranger approaches them for a quickie.

Why is this example used?

This experiment has been repeated a few times since the original. You can see fun examples of it on YouTube, and Clark himself repeated it in 1982, and as recently as 1990 (with similar results). Failing any dramatic changes in societal norms around sex, I'd expect the results to be similar if it were repeated today.

But that's not particularly surprising. The experiment and the bar example both offer a very specific type of sex. The type of sex that, rightly or wrongly, is associated with male desire and fantasy. Whether this is fantasy is biologically led, socially implanted, or simply a massive and mistaken generalisation on our part, it is nevertheless accepted as true, and provides the foundation on which the bar example is built. Seen from this angle, the bar example fruitlessly begs the question, and amounts to no more than saying "men are likely to accept the kind of sex that we think men like".

This tells us nothing about levels of female sexual desire, or whether we are indeed in a privileged position when it comes to sex. In fact, any attempt to draw conclusions about female sexual need based on a sexual offer defined by male fantasy is as good an example of male privilege as anything else.

I like sex more than some people, but less than others. You like different types of sex to me. There are hundreds of different things that prompt our decision to say "yes" to this particular person but "no" to that one. But whether it's society, biology, anecdote or sheer loneliness that prompts our sexual interactions, it's deeply unhelpful to tell women that they are privileged just because they can walk into a bar and have casual sex. It's much more interesting, surely, to ask: why are we trying to define desire across an entire species by using this one limited sexual option?

Girl on the Net tweets at @girlonthenet, and her dirty book, My Not-So-Shameful Sex Secrets is available from Amazon (and other digital booksellers)