Two leading American papers, the Wall Street Journal and USA Today are planning scented ads.

They hope the innovation will boost their ad income. The two papers are working with a company called Scentisphere, which markets a product called Rub'n'Smell.

Of course scratch and sniff ads have been around for many years - notably for perfume ads. But that system is complicated. The biggest difference is that Rub'n'Smell is applied directly to printed ads as an ink. No separate press run to create the scented inserts is necessary.

Another big difference the new process is a lot cheaper. Until now there has been no way for advertisers to promote their product by smell economically. Advertisers also had the additional expense of having to pay to have their scented ads specially inserted into magazines or newspapers.

Said Bob Bernstein, president of Scentisphere: "With our technology the scented capsules go right into the printing press."

That brings down the cost between 20 and 30 per cent. Will advertisers go for the new ads? Scent, it is claimed, is the strongest memory trigger. And earlier tests with the old method have provided evidence of increased sales. His company claims the new product can increase sales up to 25 per cent.

Already in stock are such scents as grass, leather and chocolate. But creating a special scent it is claimed is not too expensive - between $1,500 and $ 2000.

So far neither USA Today nor the WSJ have disclosed when their first scented ads will run but they are expected shortly.