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Wide eyes, raised eyebrows, flaring nostrils and a dropped jaw are recognized around the world as the facial expressions denoting fear. Consider Edvard Munch's iconic painting The Scream. You don't need an art critic to tell you the figure in the portrait isn't a happy camper.

But it may be more than just a coincidence that people from all cultures show terror in the same fashion. In fact, Charles Darwin, the father of modern evolutionary theory, suggested in the 19th century that some common facial expressions may bestow a survival advantage.

Now, researchers at the University of Toronto have conducted a series of experiments that demonstrate the distorted facial features of fear may actually enhance our ability to spot danger.

"If you are in a situation facing an uncertain threat, you want to increase the likelihood of seeing it and responding to it quickly," said Joshua Susskind, one of the authors of the study published in the journal Nature Neuroscience.

In particular, bulging eyes can sharpen vision and open airways heighten the sense of smell.

For the study, the research team led by cognitive neuroscientist Adam Anderson asked a group of volunteers to mimic fearful expressions.

Tests revealed that the subjects' field of vision increased substantially and their eye movements also sped up.

One volunteer was scanned by a magnetic resonance imaging machine while donning a fearful face. That high-tech analysis showed the internal nasal passages widened, allowing the subject to breathe in more air.

"The conventional view is that facial expressions simply communicate our inner feelings," said Mr. Susskind, a graduate student working in Dr. Anderson's lab.

"Our position is that fear is a vigilant posture," he said. And the classic facial features of fear "allow you to better scan your environment for potential attackers ... and prepare you for a flight-or-fight response."

Other facial expressions are probably shaped by function and biology, too. The researchers also investigated expressions of disgust, in which the facial features become scrunched up or pinched together. In this case, "you're blocking off your nasal passages and closing off your eyes" to something you don't want to experience," he said.

MIND GAMES

Forget about performance-enhancing drugs: Athletes might be better off harnessing the powers of the mind - or, at least, the placebo effect.

Researchers at the Garvan Institute of Medical Research in Sydney divided 64 young recreational athletes into two groups. One received growth hormone, a substance banned in professional sports, while the other got an inactive placebo.

At the end of the eight-week trial, the participants were asked if they thought they had been given the real treatment or a placebo.

"Half the athletes wrongly thought they were on growth hormones," one of the researchers, Ken Ho, told an online news conference from the Endocrine Society's annual meeting in San Francisco.

"We found that athletes who believed they were taking growth hormone actually felt their performance had improved and actually demonstrated improvement in physical performance even though they were taking a dummy drug," he added.

Dr. Ho attributed the increase in performance to the well-recognized "placebo effect" in which people feel better, and may even do better, because of the belief they have received a beneficial treatment.

Although growth hormones can help bulk up muscles, there is little good scientific evidence showing the drugs enhance athletic performance, Dr. Ho noted.

"It is clear from our study that the mind plays amazing tricks on the body," he said. "I just wonder whether some of the achievement in sport is due to the power of the mind, rather than the substances that have been dished out to athletes."

AIDS TESTING FOR THE AGED

Sex isn't just for the young - and neither is AIDS testing.

Recent studies have found many people maintain an active sex life well into old age. That means they are potentially at risk of contracting the disease or spreading it to others, said Ahmed Bayoumi of the Centre for Research on Inner City Health at St. Michael's Hospital in Toronto.

In 2006, the latest year that statistics are available, 14 per cent of all new HIV-positive cases involved people over the age of 50.

"In larger metropolitan areas in Canada, it likely makes economic sense to institute generalized screening for HIV [the virus that causes AIDS], including people aged 55 to 75," said Dr. Bayoumi, co-author of a study on AIDS tests in the journal Annals of Internal Medicine.

"If you are older, and you have never been tested, then you should probably get at least one test for HIV because the incubation period is very long. You might not know for years you are HIV-positive."

With a proper early diagnosis, "we can initiate therapy that can keep a person healthier for much longer," he added.

ptaylor@globeandmail.com