As the nation braces itself for a summer of reality TV, Nick Morrison looks at why we enjoy watching people humiliate themselves - and why we're lining up to be humiliated.

A COMEDIAN peers at the contents of his recently-evacuated colon; a dinner party guest is ridiculed and told she's a fat monster; a father tells his family he is going to live on a tropical island and will never see them again; a young man tells his girlfriend he's gay - even though he's not. Welcome to a summer of reality TV.

We've already had I'm A Celebrity, Get Me Out Of Here! and Celebrity Detox Camp, we're in the middle of Big Brother 4, and delights yet to come include The Dinner Party Inspectors, The Pilot Show and My New Best Friend. There seems to be no end to our appetite for reality TV, and this summer they're pushing the boundaries further than ever before.

It seems it's not enough to drop in on people's lives: we want to see these people squirm. We want to see them in tears; we want to see them angry; we want to see them humiliated. In short, we want to be cruel.

"We're becoming a nation of voyeurs. It is cheap titillation, cheap entertainment," says cultural criminologist Mike Presdee, of the University of Sunderland. "In Big Brother, people want to know if they're having sex or want to watch them going to the toilet.

"But it has got more focussed on the art of the put-down, and it is about being cruel as fun. It is fun, but it isn't harmless fun."

Hot on the heels of What Not to Wear is The Dinner Party Inspectors, where Trinny and Susannah clones gatecrash dinner parties and tell the host, and the guests, exactly what they think of them. In one episode, a guest is told she is "a fat green-eyed monster eating salad like a demented rabbit".

The Pilot Show dupes members of the public into taking part in spoof pilot shows. In one, a dad tells his family he's going to live on a desert island populated by lap dancers. Following that is My New Best Friend, where contestants are given a new best friend, and have to do whatever the friend tells them. In one, a young man tells his girlfriend he is gay, in another, a woman tells her family she is to star in a porn film.

As well as the voyeuristic element, there is a part of us which rejoices in seeing other people suffer. According to Mr Presdee, this is partly a reaction to the constraints on our behaviour in public. If we can't be rude in public, at least we can laugh at them in private.

"It's a very politically correct world at the office or in school, and then we go home and turn on the telly and have a good laugh at people's expense. The more talk there is of anti-social behaviour, and the more the Government tries to control us, the more people will respond in these sorts of ways," he says.

"We're becoming more and more and more restricted, and that builds up the pressure, and then you go home and let it off. The problem is, we're hurting somebody along the way."

Instead of turning to high drama, or indeed any TV which makes us think, we want something immediate, something we can just sit back and absorb. And if we've had a hard time at work, we want to see someone else having a hard time.

The last time watching others suffer became such a spectator sport it involved lions, gladiators and coliseums, but, although there are similarities with the Roman Empire, it is possible to take the analogy too far.

"It is not the same as bread and circuses, as being cruel in Roman times," says Mr Presdee. "We're not chopping people's legs off, although we are hurting them mentally, and once it has been played out in front of millions of people, there is no escape."

But if reality TV is so humiliating, why do people take part? According to Dr Joan Harvey, chartered psychologist at Newcastle University, it is a mixture of a thirst for fame and naivet.

"They think there is going to be instant fame and instant rewards, and potentially a better job," she says. "And I think they largely go into it without really realising what they have let themselves in for. People think they can handle it and they will get some form of notoriety. Some of them do have a local amount of fame for a little while, but it will die off."

As well as our natural voyeurism, we also enjoy watching people come a cropper. Whether it's a professional skier taking a tumble, or a celebrity breaking down in tears, few sights cheer the spirit as much as observing a downfall. And what it makes it particularly satisfying when you're watching reality TV, is the knowledge that these people volunteered - they're asking for it.

"We know they subjected themselves to it to get some quick fame, so we enjoy it when it turns in on itself. If there's somebody who will do anything for publicity, we're chuffed when they get their comeuppance," says Dr Harvey. "We know they have set themselves up - I wouldn't go on a programme that allowed people to pick me apart."

Experience may show that reality tv humiliates those who take part, but the number of people willing to sign up suggests the navet may be very deeply ingrained.

Mr Presdee: "We know the amount of footage on something like Big Brother is huge, and we only get to see a bit of it. People go on these programmes and have no idea how programmes are put together.

"It gives me a certain sadness that we're publicly humiliating people who have done nothing wrong, apart from being part of these programmes."

But isn't it all just harmless fun? Ok, so someone gets humiliated, but no one's really getting hurt, are they? Well, according to Mr Presdee they are, and it's not just those taking part who suffer.

"We know that those who brutalise others are brutalised in the process, even if it means they might well be willing to personally humiliate somebody, because they have seen it being done and think it is good fun," he says.

"It is good fun, but it is also a form of mental cruelty. Domestic violence is not just physical, it includes mental violence, so what is the difference? Being cruel to somebody isn't just beating them up."

But when humiliation is officially sanctioned by Government - what is naming and shaming if not public humiliation? - is it any wonder that we revel in it so thoroughly? According to Mr Presdee, the only consolation is that it is a response to the pressures of not behaving badly.

"It isn't human nature to be cruel. This is a result of something else that is going on, and I would look at the amount of control we're subjected to. When we get the chance to see things we know we shouldn't see, we take it, and because it's in our own homes we can do it without being found out. It is fun and we all laugh at it, but it isn't harmless fun. It is fun with harm."