Music smell theory stinks, say scientists

A RADICAL theory that the sense of smell is based on molecular vibrations has been dismissed by scientists.

The theory, which is the brainchild of the perfumer Luca Turin, a former scientist at University College London, says the nose detects odours from variations in the molecular vibrations of scented substances – a sort of music for the olfactory organs.

It was put to the test by Andreas Keller and Leslie Vosshall of Rockefeller University in New York in a series of experiments. In their study, published in the journal Nature Neuroscience, they failed to find support for the vibrational theory, but uncovered evidence for the conventional view that smells depend on the shape of molecules.

They found that 21 volunteers could not tell the difference between the normal form of the scented chemical acetophenone and its isotopic form, whose molecules have the same shape but different vibration frequency. Two further experiments also failed to support the vibrational theory. Professor Voshall said: “It shows us that molecular vibrations alone cannot explain the perceived smell of a chemical,” she said.

However, the “shape theory”, which posits that olfactory receptor proteins bind like a lock and key to scent molecules of a given shape, is limited in that there are only 347 different odour receptors dedicated to smell, yet humans are able to discern many times that number of smells.

Dr Turin, who was lionised in a BBC Horizon documentary and in a book, The Emperor of Scent by Chandler Burr, said: “The jury’s still out. Two out of three of her experiments are irrelevant and the third, although highly relevant, is just one of a number that have produced contradictory results.”