London: The human nose has evolved to sniff out the smell of danger, according to research. Scientists found volunteers, who were previously unable to differentiate between two similar scents, learnt to tell them apart when given electric shocks alongside just one of them.

They said this demonstrated how experiences help sharpen our senses to keep us clear of danger. The researchers also suggested people with less ability to distinguish between important and irrelevant signals may be more likely to suffer from illnesses characterised by anxiety and vigilance such as Obsessive Compulsive Disorder (OCD).

Lead study author Dr Wen Li of the Feinberg School of Medicine Northwestern University, Chicago, said, It's evolutionary. 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.

The ability to discriminate between biologically meaningful cues such as the smell of a 175 kg lion and similar but irrelevant stimuli such as the smell of a 3 kg cat maximises an organism s response sensitivity while minimising hyper-vigilant and impulsive behaviours, he added.