The new studies, one of which was published Friday in the peer reviewed Scandinavian Journal of Immunology, found significant differences in the immune systems between euthanized wild and lab rodents.

When the immune cells in the wild rats are stimulated by researchers, "they just don't do anything they sit there; if you give them same stimulus to the lab rats, they go crazy," said study co-author Dr. William Parker, a Duke University professor of experimental surgery. He compared lab rodents to more than 50 wild rats and mice captured and killed in cities and farms.

Also, the wild mice and rats had as much as four times higher levels of immunoglobulins, yet weren't sick, showing an immune system tuned to fight crucial germs, but not minor irritants, Parker said. He said what happened in the lab rats is what likely occurs in humans: their immune systems have got it so cushy they overreact to smallest of problems.

"Your immune system is like the person who lives in the perfect house and has all the food they want, you're going to start worrying about the little things like someone stepping on your flowers," Parker said.

Challenged immune systems - such as kids who grow up with two or more pets - don't tend to develop as many allergies, said Dr. Stanley Goldstein, director of Allergy & Asthma Care of Long Island.

Parker said his study has drawbacks because he can't be sure that the age of the wild and lab rodents are equivalent, although he estimates the ages based on weight. He also could not control what happened in the past to the wild rats to see if they had unusual diseases before being captured and killed.

It would have been more useful had Parker studied extremely young wild rodents because, according to the hygiene hypothesis, that's when the protection from dirty living starts, said Dr. Stuart Levy, director of the Center for Adaptation Genetics and Drug Resistance at Tufts University.

Human epidemiological studies have long given credence to the hygiene theory, showing that allergy and asthma rates were higher in the cleaner industrialized areas than in places such as Africa. Parker's studies, looking at animal differences, may eventually help scientists find when, where and how environmental exposure help protect against future allergies and immune disorders, said Goldstein, and Dr. Jeffrey Platt of the Mayo Clinic in Minn., both of whom were not part of Parker's studies.

Parker said he hopes to build a 50-foot artificial sewer for his next step, so that he could introduce the clean lab rats to an artificial dirty environment and see how and when the immunity was activated.

That may be the biggest thing to come out of the wild and lab rodent studies, Platt said: "Then all of a sudden it becomes possible to expose people to the few things (that exercise the immune system) and gives them the benefit of the dirty environment without having to expose them to the dirt."

This brain activity may reflect the fact that exploring new options requires overriding the desire for immediate profit.

Dr Daw, UCL Gatsby Computational Neuroscience Unit, said: "Whether you are a stockbroker, a gambler choosing between slot machines or an animal trying to forage for food, the desire to select what seems the richest option is always balanced against the desire to choose a less familiar option that might turn out to serve better. This exploration is often critical to survival.

"Most people switch between exploring and exploiting seamlessly and this has always made it hard to distinguish between someone who is doing something they know will offer the highest pay-out and a person who is testing out new options. By using some of the systems used to program robots to learn and make decisions, we have now found which areas of the brain are responsible for these different behaviours."

The team studied the behaviour of 14 subjects while they were gambling for money using on-screen slot machines. To find out whether the subjects were using exploitative or exploratory gambling strategies, the team compared the human behaviour with the decisions made by intelligent robots. fMRI scans were used to measure brain activity to show which brain areas were activated when exploring or exploiting.

After the task, subjects were asked to describe their choice of strategies. The majority of subjects reported occasionally trying the different slot machines to work out which had the highest payoffs (exploring) and at all other times choosing the slot they thought had the highest payoffs (exploiting).

"The high value of space systems has led the United States to study the potential of space-related weapons to protect our satellites from potential future attacks, whether from the surface or from other spacecraft. As long as the potential for such attacks remains, our Government will continue to consider the possible role that space-related weapons may play in protecting out assets," Mohanco noted.

In response, one space peacenik told me: "Pretty strong statement...the party line in the past was to avoid the mention of space weapons and simply tout the "we don't need no stinkin' treaty" line.