Tom Sutcliffe: Comic timing's no laughing matter

The week in culture

We often hear, from dramatists and actors, about the magical togetherness that theatre can create in an audience – those special moments which are the product of a live performance meeting collective attendance, and which can't easily be replicated in any other art form. This, it's frequently implied, is theatre's sacred edge over some of its competitors. So, while you can react in synchrony with others in a cinema, the film can't react back.

It can't catch a mood of an audience and amplify it. What isn't as often discussed, though, is the downside of that theatrical virtue – the fact that when we stop being individuals and behave as a collective organism bad things can happen as well as good. I don't want to over-dramatise this. A London theatre audience can be an unlovely spectacle at times, but I don't think I've ever seen one turn into a mob. And while I've certainly been at plays that stroked an audience's sense of self-regard, I can't recall ever seeing one that attempted to co-opt them for a sinister purpose. Trying to bump up the sales figures for the cast-recording of Love Never Dies really doesn't count.

There can be something uncomfortable about the obedience of an audience, though, that biddable willingness to respond to theatrical cues, even if the cue doesn't really correspond to anything. It's most obvious with laughter and there was a good example of it the other night at 13, the first night of Mike Bartlett's play about a messianic figure agitating for social change. In one scene, an old lady called Edith talks about a recent case brought against her for ramming a shopping trolley through a bank's front window. Her lawyer tells her he's managed to get them to drop the case, at which point she sets off on a long tirade about the terrible service that had provoked her attack in the first place. "It's shit," she concludes. "It's a shit bank." And, not entirely surprisingly, the audience roars. Two reliable buttons have been pressed. An old lady is using bad language – which almost always makes audiences chuckle condescendingly – and someone is having a go at a bank. Then, after a pause, she names the offending institution. "It was NatWest, if you want to know," she says. And the audience laughed even louder.

I was a little puzzled by this. Could there really be that many disgruntled NatWest account holders at the first night? And if not, what was so galvanising about this moment? And to that there were two answers, I think. The first was that we don't often hear brand names in the theatre, so there was a tiny sense of transgression there. And the second was that there wasn't really anything very galvanising at all. It isn't that NatWest particularly deserves our opprobrium right now or has a particularly funny name. It was just that the line had the shape and timing of a punchline and the audience understood what was expected of it. I can't be sure, of course. If you don't laugh when others do there's always a chance that you're out of step, not them. It had happened to me a few days earlier at April De Angelis's play Jumpy, where the comic rehearsal of a burlesque routine had reduced an entire theatre to honking helplessness. All I could see was the psychological implausibility of the moment and waited in silence for it to pass. On that occasion, there was no doubting the audience's sincerity but in 13 it was hard not to feel that being in step was the relevant metaphor. Would any of those people have laughed aloud if they'd watched this scene alone? I doubt it. They laughed because the play had instructed them to.

That needn't always be pernicious, of course. It's one of the joys of a stage comedy that an audience can whip up its own momentum – as we all give each other permission to laugh. But you may find yourself wondering later exactly what it was you were laughing at – and asking yourself whether civil disobedience shouldn't have its place in an auditorium too. The line between a community and a herd isn't always easy to see before you step over it.