Does listening to classical music make babies smarter? Opinion is divided; while most experts are skeptical, many moms remain firm believers of the Mozart effect -- a theory that classical music boosts IQ. Some eager expectant moms even start playing classical music while the baby is still inside the womb, hoping to give the baby-to-be an early headstart.

The Mozart effect was first reported in 1993 by scientists at the University of California-Irvine, who found that listening to Mozart sonatas improved the spatial reasoning of college students. The effect was only temporary, but people immediately jumped to the conclusion that classical music improves intelligence, and the earlier people started listening to it, the better. Thus, the notion that babies would be smarter if they listened to classical music was born out of this hype. Mothers were urged to play music for their toddlers, then their newborns... then their fetuses. In fact, follow-up studies were unable to confirm the experiments' results in adults or children.

Then Dutch researchers found that not only can late-term fetuses "hear" sounds, but they can actually "learn." The researchers exposed the fetus to a noise, then used ultrasound to see how it reacted. They found the fetus reacted to the sound more quickly each time it heard it. But there's no evidence that this early "learning" has any effect on later intelligence, either.

But if you still want to play classical music to your unborn baby, go right ahead. "It can't do any harm," says Lise Eliot, Ph.D., assistant professor of neuroscience at The Chicago Medical School, and author of What's Going on in There? How the Brain and Mind Develop in the First Years of Life. "And maybe it even helps... in the sense that a mother who would take the trouble to read to or play music to her stomach is probably very motivated to take good care of her baby when it arrives!"