Ever noticed how many Olympians bite their medals for the cameras?

Chinese Internet surfers have, sparking speculation about the origins of the practice and whether biting is not just for the cameras but has psychological benefits.

The custom of biting a gold medal could stem from an ancient method of testing the value of gold with one's teeth. The purer the gold, the softer the coin.

At the Olympics, the biting is largely fuelled by the calls of mainly European photographers: "Kiss it, bite it."

"There are too many shoddy products around these days. Could the gold medal be fake too? Better check!" said one entry on a Chinese Internet forum post.

Gold medals winners may be disappointed. Gold medals are actually made of 92.5 percent pure silver plated with at least six grams of gold, in accordance with the Olympic Charter.

But web surfers have come up with other theories too.

One report on www.qianlong.com, a Beijing-based news website, quoted an unnamed "expert" as saying the custom was a Freudian reversion to oral stimulation after the stress of competition.

Romantic observers believe a kiss is not enough to show affection for the medal and a love bite is better.

"They want to know how a gold medal tastes. They ate enormous bitterness before receiving gold medals," wrote Leonardo on one chat forum.

Nearly every gold medallist and many silver and bronze winners have been asked to bite their medal in the 2008 Games, according to Reuters photo editors, sometimes resulting in an unattractive snarl.

"A lot of people, especially the Chinese athletes, really don't know what to do with it, so they just rub it against their lips in a very awkward way," said freelance photographer Natalie Behring.