Are people biologically programmed to distrust strangers?
A new study that shows humans' sense of smell is far more sophisticated than scientists once thought seems to suggest this may be the case. In fact, just a whiff of a stranger's body odour is enough to activate parts of the brain involved in the perception of fear.
For the study, a group of women were asked to sniff four different odours - their own, a stranger's, a friend's and an everyday, non-body odour - while their brains were scrutinized by a PET (Positron Emission Tomography) scanner. (The body odours were collected by having the women - some friends and some strangers - sleep in T-shirts with cotton pads sewn into the armpits.)
The results of the study, conducted by researchers at the Montreal Neurological Institute of McGill University, revealed that body odours are processed by an entirely different nerve pathway in the brain than common odours.
They also discovered that a stranger's body odour activates the same regions in the brain that are known to respond to fear or danger, said lead researcher Johan Lundstrom, who recently started a new job at the Monell Chemical Senses Center in Philadelphia.
Furthermore, when asked to categorize the smells, the women consistently rated a stranger's odour as "more intense and less pleasant" than the body odour of a friend.
Dr. Lundstrom speculated that our finely tuned sense of smell probably evolved in the distant past as part of a survival mechanism.
"Stimuli that are perceived as very important ... for our survival ... are processed faster and more accurately by special neuronal networks," he said in a statement released with the study, which was published in the journal Cerebral Cortex.
"A stranger's body odour is a behaviourally important stimulus because it is unfamiliar and might signal danger. Therefore, the brain has developed a mechanism to ensure that it grabs our attention."
DON'T DRINK THE SANITIZER
British hospitals are being urged to "lock up" their hand sanitizers because a growing number of patients have become sick from drinking the alcohol-based solutions.
In today's issue of the British Medical Journal, toxicologists report there has been a spike in poisoning cases after hospitals started placing hand-sanitizer dispensers at bedsides and near ward entrances as a way to reduce common infections.
In some cases children or confused adults downed the noxious fluid, mistaking it for water. In other cases it was intentionally consumed by substance abusers trying to get high.
The British toxicologists who wrote the report recommend that large hand-sanitizer dispensers be placed in secure holders to prevent accidental or intentional removal by high-risk patients.