Are you an Oscar or an Elmo?

As a nation, we're not a very optimistic bunch. We're more likely to relate to Sesame Street's Oscar the Grouch than his cheery neighbour Elmo.We've been granted the honour of hosting the Olympic games, but according to an Ipsos Mori poll, 55 per cent of us would rather bemoan the transport network while the Games are on, and more than half a million would prefer to leave the country completely than celebrate.

It's standard practice to distrust bankers and politicians (and journalists, for that matter), but, according to the Edelman Trust barometer, which measures trustworthiness, Brits have gone a step further, and now distrust executives irrespective ofprofession.

The barometer also found the UK is one of the most distrustful countries in the world. Plus, we don't think things are going to get any better. In 2011, 48 per cent of us saw ourselves as either "struggling" or "suffering" on a Gallup index of wellbeing, and didn't expect any improvement over the next four years. On top of it all, we are currently experiencing one of the rainiest summers ever. It's all very depressing.

But alongside this staunch pessimism resides an unsettling feeling that we should be more positive. We are always trying to dislodge each other's pessimism. Test it for yourself; sit gloomily in a public place and see how long it takes before a Elmo-type passer-by says, "cheer up mate/love, it might never happen!" or offers one of those trite aphorisms about looking on the bright side, silver linings or closing doors.

The self-help industry, which peddles hope and positive thinking, is still raking in billions while other industries are faltering. So, while steeped in cynicism, it seems we're still looking for a way to feel more positive. But what can a positive outlook really do to improve our lives? How can optimism make bankers more trustworthy, or the Olympics more successful, or stop this incessant, miserable, rain?

It can't, says the neuroscientist Elaine Fox, a visiting research professor at Oxford University, who recently published the book Rainy Brain, Sunny Brain – about our ambivalent feelings of optimism and pessimism. Our negativity is the response of a rational mind and positivity is a delusion, she says, and for most of us, they both act to balance us out. "Positivity is a delusion. But it is a useful delusion. If we didn't have some sort of optimism we wouldn't ever get out of bed in the morning. But pessimism has its place," she says.

So, when we think positively, are we just tricking ourselves that things will get better? It's a little more complicated than that, says Professor Fox. Aside from getting us out of bed, it can actually help in other areas of life, but not in the way the self-help books might have you believe. "Where self-help books say, 'just think happy thoughts,' it doesn't work," she says. But some degree of optimism can work to our advantage, because if we feel more positive, we will take more positive actions, and reap the rewards.

"Optimism helps you with persistence and gives you a sense of control," Professor Fox explains. "If you have a mother with a toddler and the toddler is running to a busy road, but the mother just stands there and thinks happy thoughts, the child will not be saved but if she acts positively and runs to save the child, the child stands a better chance of rescue." So, if we just told ourselves the mantra, "the Olympics will be amazing, the Olympics will be amazing" it won't make it happen, but if we used our positivity to take action – by buying tickets to events, or even getting involved as a volunteer, we might have a better chance of enjoying it.

More dramatically, positive thoughts can have concrete health benefits. Professor Fox interviewed the actor Michael J Fox (no relation) as part of her research to find out how he dealt with being diagnosed with Parkinson's, a progressive neurological condition that affects nerve cells in the brain. "He said when he got the diagnosis he knew he wouldn't be able to continue at the level he as at, because no matter how famous you are, studios still have punishing schedules. He knew it was the end of his Hollywood career – he was a bit down but he also felt he would be able to deal with it and cope."

This is one of the times optimism can help us through, Professor Fox explains – when we are hit by disaster, optimism helps us pick ourselves back up. Professor Fox also spoke to other people who have had severe injuries or become paralysed. "They have found a different level," she says, "it is something I am fascinated by."

In experiments on pain, in which students are asked to keep their hands in a buckets of ice water for as long as they can stand it, students who believe they have been given a painkiller, but have in actual fact just been given a sugar pill, will keep their hand in longer than those who aren't given anything. Scans of their brains show they actually produce a surge of dopamine, a happy chemical, which combats the pain.

This shows that positivity can have immediate physical effects, says Professor Fox. "Thomas Edison said, 'if I find 10,000 ways something won't work, I haven't failed. I am not discouraged, because every wrong attempt discarded is another step forward,' Optimism is to do with persistence. As with the iced water, optimists will try harder and spend longer on something than pessimists, says Professor Fox. "[They] also believe they have some control over their life, and that's why they tend to be more successful."

But don't shrug off your Oscar-like cynicism just yet. Professor Fox says a healthy dose of negativity can help us out, too. "The amygdala – the fear system in our brain that helps us detect threat and danger is really at the root of pessimism. Pessimism helps us suss out danger in our lives." And although we're unlikely to need this reaction the same way our caveman ancestors did – for fight-or-flight reactions – fear is still a useful trait.

"A pessimistic outlook would work if you were setting up your own business," says Professor Fox, "to identify risk and avoid it." So, there is a place for pessimism. "They say the aeroplane was invented by an optimist and the parachute was invented by a pessimist. That's the reason I called the book Rainy Brain, Sunny Brain, because we need both."

In her work, Professor Fox found that scepticism, combined with a sort of over-arching optimism, was found in people who were successful in life and who were able to overcome knock-backs. "Having a healthy balance makes sense," she says. "A lot of optimists say, 'I am realist.' What they mean by that is that they are an optimist but in the short term they know things won't always work out. That kind of optimism with a pessimistic slant means you know you can cope with what life throws at you."

So, if you continue to hope that politicians and bankers will become honest, but treat them with suspicion, expect travel chaos during the Games, but take the Tube anyway, anticipate sunshine, but carry an umbrella, you should get along just fine.

'Rainy Brain, Sunny Brain' (£12.99, William Heinemann) is out now