Why do big, powerful countries with strong militaries sometimes lose wars to small countries with weak ones?

That is the question being asked by a researcher at the University of Georgia School of Public and International Affairs. Patricia Sullivan analysed 122 military interventions since the second world war in which the US, the UK, the Soviet Union, Russia, China or France fought a weaker adversary. The more powerful country failed to achieve its objectives 39 per cent of the time.

The most important factor for the success of the stronger nation appears to be whether its strategic objective can be accomplished with brute force alone, or requires the co-operation of the opponent. For instance, driving Saddam Hussein’s army out of Kuwait in the 1991 Gulf war, as well as overthrowing his government in 2003, were brute-force objectives - and were accomplished relatively quickly. But today’s attempts by the US to quell sectarian violence in Iraq and build support for the government there have proven much more difficult, because the efforts require the target’s compliance.

Previous researchers have theorised that more-powerful states fail because of poor strategy choices or a lack of resolve. But Sullivan points out that more-powerful countries have a greater ability to absorb losses from poor strategy choices and can more easily change strategies. Moreover, resolve - or lack thereof - fails to explain victories such as the first Gulf war, which many analysts predicted would be difficult for the US since the Iraqi army, despite being weaker, showed firm resolve.

Sullivan’s model predicts that coalition forces have a probability of success of about 26 per cent in the current conflict in Iraq. It estimates fighting will last another 10 years.

When liquids are an asset

Looking to lose weight? Time to water up - but not just with the famous eight glasses a day. A year-long clinical trial by researchers at Penn State shows that diets focusing on foods low in calorie density promote healthy weight loss, while also helping people to control hunger.

These foods, which are high in water and low in fat, include soup, lean meat, fruits, vegetables and low-fat dairy products. Eating such a diet reduces the intake of calories, while also allowing people to eat ”satisfying portions of food”, thereby keeping feelings of deprivation in check.

Fancy lighting up the pleasure centre in your brain?

Fancy lighting up the pleasure centre in your brain? Just pay your taxes, and then give a little extra money to the charity of your choice.

A team of scientists at the University of Oregon has found such deeds give the same sort of satisfaction as feeding your own hunger pangs. The team gave 19 participants $100 and then scanned their brains with functional magnetic resonance imaging (fMRI) as subjects watched their money go to the charity via taxes, and then decided whether to give more money voluntarily or keep it for themselves.

Two regions deep in the brain - the caudate nucleus and the nucleus accumbens - fired when the subjects saw the charity get the tax money. The activation was even greater when people gave voluntarily. These brain regions are the same ones that fire when basic needs, such as those for food or social contact, are satisfied.

”It reinforces the idea that there is true altruism,” said the team’s cognitive psychologist, Ulrich Mayr.