The red line shows an attempt to follow the straight scent trail

US research had confounded the established belief that people have a poorer sense of smell than animals.

The work, published in the journal Nature Neuroscience, asked people to follow scents on the ground, as a dog would do, and found they were as good.

A UK expert said the findings were "intriguing" and would aid better understanding of the sense.

It is not the second class system that has been the traditional assumption

Dr Peter Brennan, University of Bristol

The researchers from University of California Berkley laid scent trails, including one of chocolate essential oil, in a grassy field, and asked 32 people to find the 10 metre trail and track it to the end.

Those who took part were blindfolded and wore thick gloves and earplugs to force them to rely exclusively on smell.

Two thirds were able to follow the scent.

And while they remained slower than the animals at tracking scents, their performance improved over time.

In other tests, it was found that humans required both nostrils to be working to be able to track scents.

'Highly developed'

Writing in Nature Neuroscience, the researchers led by Dr Noam Sobel showed the human sense of smell was more powerful than previously believed and that, with training, humans might be capable of tasks which had been thought to be the exclusive province of non-human animals.

Dr Peter Brennan, a physiologist at the University of Bristol, said: "It's certainly an intriguing piece of research.

"It shows that although the sense of smell is less important for humans than it is for many other animals, it is nonetheless a highly developed and sophisticated sensory system.

"It is not the second class system that has been the traditional assumption."

He added: "There has been previous evidence that scent can elicit orientation and movement towards maternal odours by new-born babies, but this is the first time that adult humans have been shown to follow a scent trail."

Dr Brennan said the findings could enable specific areas of research into the human sense of smell.

"For example, it would be interesting to study the extent to which blind people make use of their sense of smell for finding their way around their environment."