Q) Do cows lying down really mean it's going to rain?
Jesse cantwell, Groveland, Illinois
Nope. Nor is it true that dogs eat grass before rain, groundhogs ruminate over their shadows, or Harvard nerds play Risk the night preceding a nor'easter. Turns out the vast majority of weather lore is bunk, though many faulty predictors endure in the age of Doppler 3000 and perfectly coiffed weathermen. This is probably because a handful of the predictors do work, mostly those based on animals' ability to detect changes in barometric pressure (something scientists don't yet fully understand). Seabirds head for open ocean when a storm system is approaching, bees tend to return to their hives during a pressure drop, and blackflies bite more before a drizzle. So chances are many of us will reach for our parkas when we see horizontal heifers. Unfortunately, says Mary Knapp, the state climatologist in Kansas (where modern wives' tales have led some to mistakenly believe they can outdrive tornadoes), "our understanding of weather keeps progressing, but the folklore doesn't keep up."

Pop Quiz

A lonely reader wants to know why she can't tickle herself. The answer is anticipation: You know the tickle monster is coming and where it's going to strike, so your body ignores the sensation. This is a desirable bit of physiological wiring—If you couldn't tell the difference between self-induced and interpersonal touching, you'd check for spiders every time your hand brushed your leg. So try to tickle yourself and the cerebellum simply yawns and says, "You again?" A tickle from someone else lights up a different part of the brain, even if you see it coming, triggering the laughing, limb-thrashing, primitive panic reaction that toddlers and Elmo live for. A 1999 study by neurobiologist Sarah-Jayne Blakemore, at the UK's University College London, showed that sneaking up on yourself with a robotic arm can increase the "tickle rating," while other research suggests there's at least one class of people capable of fooling themselves into a serious squirm: hallucinating schizophrenics, who have trouble telling if the tickle is coming from their own hand.

Q) Could a river otter and a sea otter trade places?
Sue Koehler and Paul Brogan, Orange Park, Florida
Yes and no. The term "river otter" is misleading; the playful little mustelids live in almost every aquatic environment in North America, from rivers, marshes, and lakes to the big briny off both coasts, where they stick close to shore and venture inland for freshwater. The sea otter, however, almost never leaves its marine milieu. This threatened species, with populations in California and Alaska, is outfitted with some of the densest fur in the animal kingdom, kidneys that can process salt water, and hind flippers that make them superb swimmers but poorly suited for habitat hopping. Drop one in sweet water and it'll likely survive as long as there's food—which might not be long at all. "A sea otter consumes 25 to 35 percent of its 60-pound body weight every day," explains Steve Shimek, executive director of the Otter Project, a California conservation group. "One animal would quickly decimate a small lake."

Q) Why is the human iris colored?
Nick Pedersen, Washington, D.C.
Our eye color comes from a dark pigment called melanin that's found in the iris, the muscle that dilates and contracts the pupil. The concentration of melanin occurring in most mammals results in brown eyes, but humans are born with varying amounts of the pigment, which, combined with light-scattering effects, lead to baby blues, greens, hazels, and grays. Researchers aren't sure why our eyes are colored, but one long-popular theory holds that Northern Europeans developed blue and green peepers to cut down on the glare reflecting off the region's abundant snow and ice. Another, sexier theory, suggested in a recent study by British psychologist David Perrett, is that lighter mutations in hair and eye color became an adaptive advantage of Euro cavewomen competing for mates. Blue eyes and blond hair were fresh and led to more prehistoric booty calls. Or at least that's the story Barney Rubble's mother is telling.