Recently I was up in Sheffield delivering some bisexuality awareness training at the university there. I tried out a new exercise I'd only just thought up.

One of the problems with explaining bisexuality to people who aren't bisexual is that to a bisexual person their sexuality most likely seems simple and uncomplicated, and the reasons why it is confusing to others don't seem to make sense. I'd started to think that maybe bisexuality isn't about who you're attracted to, so much as heterosexuality and homosexuality are about who you are not attracted to.

I divided the page of the flipchart into two columns, one topped with a tick and one with a cross. What things, I asked, turned people on or off about others? Not you personally, of course - that'd be awfully intrusive, but what things in general, or what things your friends have told you that they (and of course not you) find positive and negative about others.

I started the chart off with a few suggestions, like "good teeth" and "snoring" and as the columns filled some things went in both columns, like "arrogance" and "sense of humour". When we got to the bottom of the sheet I turned to the room, and asked if they could tell me what was missing?

Blank looks.

What, I said with a grin, given the subject of this session and the undoubtedly ulterior motives I have for asking the question of what goes in which column, might be missing?

I could see a couple of people's eyes widen and heads tilt, but no-one would say it aloud. So I wrote "gender" on the sheet, at the bottom.

In the "negatives" column.

Isn't it interesting, I said slowly, that in a room of mostly gay and straight people, no-one has said that a person's gender is a reason they wouldn't fancy them?

Someone protested. I was being unfair, after all I'd asked for qualities or attributes about people that others might find attractive or not attractive and gender wasn't one of those it was um, er, ah, oh....

I thanked them and said, yes exactly! Gender, to people who are only attracted to one, is such a big turn off that it's hard to spot. It's too close to the observer and so it's like it's out of focus. By the time you find out that Lee is into football and tickling and martinis it's too late - the fact that within seconds of meeting Lee your brain categorised them as male means they were out of the running. This is why society finds androgyny a threat - some people don't want to start fancying the lead singer of Hansen and then only later find out he's not female. Slipping past the big exclusion startles people.

A straight guy, or a lesbian woman wouldn't find all women attractive. A gay guy or a straight woman wouldn't find all men attractive. Of course not - they'll all have some things that turn them on and other things they don't care about. But having a gender turn-off is perhaps what makes them not bisexual. Bisexuality isn't about what we find attractive, because that's going to be different with every bisexual person (and sometimes will be based on preferences around anatomy or gender presentation, sure) but perhaps it is about not having a blanket turn-off based on the big two genders.

Bisexuals don't find everyone attractive. Have you met everyone? They're just not that attractive! But although you see Chloe leaving her girlfriend for a man, she sees herself as going from one person who shares her interests to another, possibly another who isn't cheating on her.

Heads were nodding and clues were being taken in, and the rest of the session went very well, especially when they realised that I really did mean it about answering absolutely any questions. I got to recount my coming-out-to-my-parents story (recently reprised for the recording of a show on Radio 4) and other useful anecdotes. It's handy not to need to preface with "some people have said that when they..." because a lot of it has happened to me personally.

Sheffield was a lot of train travel for only a short workshop in terms of time, but I think we all learned a valuable lesson. They got clued up about bisexuality and I found another way to rearrange the explanation to help people get it, and came home feeling very rewarded by the smiles, thank yous and eurekas.

Even if we wanted to (and I don't personally), I think it's too late to rename our sexuality. But I'm definitely going to re-use this exercise, and I heartily recommend it if you find yourself struggling to explain just how amazingly simple bisexuality really is.