By Fiona MacRae

Last updated at 19:23 27 March 2008

Arsene Wenger can sniff out trouble on the pitch for Arsenal

It has long been held that some people have a nose for trouble. Now scientists have shown we really can sniff out danger.

Research shows we quickly learn to link smells with bad experiences, enabling us to avoid the same pitfalls later in life.

It is thought our ability to sniff out danger has its roots deep in evolution, with the ability to distinguish between the scents of different animals crucial to the survival of our prehistoric ancestors.

Even today, there are obvious benefits to be had from being able to tell the difference between the smell of a 30-stone lion and that of a half-stone tabby cat.

Researcher Dr Wen Li said: "This helps us to have a very sensitive ability to detect something that is important to our survival from an ocean of environmental information.

"It warns us that it's dangerous and we have to pay attention to it."

To establish whether people can actually sniff out danger, Dr Li, of Northwestern University in Chicago, looked at how easily we can tell scents apart.

Twelve men and women were given three grassy scents to sniff.

In each case, two of the smells were the same, while the third was slightly different chemically, but virtually indistinguishable to the nose.

Asked to tell which scent was the odd one out, the volunteers got it right just one time in three - a success rate no better than chance.

However, when they given an electric shock as they breathed in one of the smells, they quickly learned to distinguish it from the other.

Scans showed the smells were also stored differently in the brain after shock treatment.

Writing in the journal Science, the researchers said the trait allows us to predict dangerous situations while minimising the need to be constantly on the alert.

Defects in the system could lead to anxiety disorders.

They said: "Learning to associate sensory cues with threats is critical for minimising aversive experience.

"Clinically, our data raise the intriguing possibility that neurobiological derangements in the ability to distinguish between salient cues and perceptually related inconsequential stimuli may underlie the emergence of anxiety disorders characterised by exaggerated sensory activity and hypervigilance.

"This may provide a unique mechanistic framework for the development of new therapeutic interventions."