Smell depends on which nostril you sniff through, scientists have discovered.

Researchers from the University of California at Irvine found that, on average, smells were rated as more pleasant when volunteers sniffed through the right nostril.

However, the left nostril was more accurate when identifying different odours.

New Scientist magazine reports that Dr Larry Cahill and his team asked 32 volunteers to sniff eight common odours, including lemon and peppermint.

The volunteers had to smell the odours through one nostril and rate them for pleasantness on a scale of ­5 to +5, and also try to identify them.

They came back later to repeat the test with the other nostril.

Brain processes smells

Dr Cahill says the findings fit with ideas about how the brain processes smells.

Earlier research suggested that each nostril sends almost all its sensory information to its own side of the brain.

Because the right hemisphere of the brain controls emotional processing, this could explain why smells might be perceived to have a different degree of pleasantness when sniffed through the right nostril.

Dr Cahill said: "Your emotional reaction to an odour actually depends on which hemisphere does the processing."

He hopes to use brain imaging to watch how the two hemispheres respond to the same odour.

Mr Robert Slack, an ear, nose and throat surgeon at the Royal United Hospital in Bath, said: "This finding does not surprise me. Different sides of the brain do different things."