Some scientific whizzes have been studying how people taste the fizz in their carbonated drinks.

It's a tricky question, since the human tongue is supposed to sense just five flavors: bitter, sweet, salty, sour and umami, sometimes called savory.

Researchers from the University of California, San Diego, and the National Institutes of Health say it's the sour taste buds that render the so-called "taste" of carbonation. They made the discovery in mice, whose sense of taste resembles that of humans.

The researchers say the tingly taste is actually caused by carbon dioxide, not the bubbles themselves. Scientists say humans may have developed sensitivity to carbonation as a protective mechanism, possibly to avoid eating spoiled, fermenting foods.

The study is in today's edition of the journal Science.