An earful: Listening while driving as dangerous as talking

Q. Even if you're careful to refrain from cell phoning while driving, what allied form of carelessness might develop as you carpool to the office? –A.G. Bell
A. All it takes is for one of the passengers to talk on a cell phone, and the driving may well suffer, according to Lauren Emberson and colleagues at Cornell University, as reported by David Schoonmaker in American Scientist magazine. Human speech is relatively predictable when we overhear dialogue or monologue, but when we hear only half a cell-phone conversation– what the researchers call a "halfalogue"– we have much less information about what is coming.

In the study, it was the information content of the halfalogue that was the culprit, since when Emberson rendered the words unintelligible yet preserved the acoustics, the distracting effect disappeared. While it is well established that driving while talking on a cell phone impairs performance, says Schoonmaker, "This is the first time that listening to passengers talk has been implicated."

Q. What's one of the more mysterious and exotic objects in your bathroom– even if you don't always look at it that way? –S. White
A. Consider an everyday mirror: light from the reflected object hits the mirror's surface and makes electrons move and emit light that makes us think there's something there though there really isn't, says Richard A. Muller in The Instant Physicist.

This is similar to a hologram, where laser light makes electrons move and emit light that creates a sort of 3-D effect. Yet the reason people are taken by holograms but not by mirrors is that mirrors are so common today. Only a few centuries ago, good quality mirrors were expensive, rare, and much valued.

Interestingly, the Biblical phrase "through a glass darkly" (1 Corinthians 13) refers to the poor images seen in ancient mirrors. By comparison, today's mirrors are minor miracles, so good that a hall of mirrors can completely confound. Mirrors are also used by magicians who know that people can't distinguish a good reflection from reality.

"They produce a much better image than a hologram does. So next time you look in a mirror, take some joy at this amazing high-tech device," says Muller.

Q. Not to gross anybody out, but doesn't the last sip of a soda become about 90 percent saliva from the repeated mouth backwash? –R. C. Cola
A. Previously, only "swish" and "hold-it-up-to-the- light" tests had been performed that he knew of, says microbiologist Dr. Ian York.

But this didn't satisfy the scientist in York, who as a post-doctoral research fellow felt a more quantitative experiment was called for. So he drank a mug of water (not soda, because sugar throws things off), sampling the protein concentration at the start and finish.

"I used a sensitive protein detection assay to quantify the amount of saliva," he said, and a comparison standard ranging from 1 part saliva in 2 parts water all the way down to 1 part saliva in 200 parts water. And the upshot was– cheers! The amount of saliva turned out to be less than 1 percent of the final sip.

"I made no particular effort to drink either carefully or sloppily; but
, obviously, someone with a more primitive drinking style may have different results," York conceded.

Q. If there were a school of shark dentistry, what might students read in the text? –R. Scheider
A. Sharks that feed on whole fish or larger prey have razor-like teeth, those feeding on crabs and lobsters, which would damage sharp teeth, have flat ones arranged like paving stones, says R. McNeill Alexander in Animals.

Most gray sharks have long slender spikes on the bottom and broad triangular cutting edges for uppers. With prey firmly in mouth, a gray shakes its head back and forth violently, using the inertia of the victim's body to hold it steady as the teeth buzz-saw on through. As teeth wear down, new ones develop in the rear of the mouth, then slide forward in a layer of skin covering the jaw. For at least one type of shark, teeth move forward at a rate of a row every eight days.

Send Strange questions to brothers Bill and Rich at