Human sense of smell far more refined than previously thought

What does your nose know? A lot more than you might expect.

Scientists studying the breadth of people's sense of smell find that the human nose can discern far more than the 10,000 different odours long cited as the outer limit of a person's olfactory abilities.

They concluded that the human nose can differentiate an almost infinite number of smells - more than a trillion - based on their extrapolation of findings in laboratory experiments in which volunteers sniffed a large collection of odour mixtures.

"The single most important contribution of this research is that it revises this current idea that humans are terrible smellers," said Leslie Vosshall, who heads the Laboratory of Neurogenetics and Behaviour at Rockefeller University in New York that conducted the study published in the journal Science. "We're very good smellers," Vosshall added.

As with sights and sounds, people are accosted with a multitude of smells, such as perfume, body odour, rose blossom, beer, rotten egg, paint, cut grass, spoiled milk, fresh popcorn, dog breath, burning wood, ammonia, grilled meat, orange peel, pine, excrement, cinnamon, exhaust fumes, biscuits and skunk spray.

Research has shown that people can distinguish several million different colours and about 340,000 audio tones, but the dimensions of the sense of smell had remained a mystery.