The phrase "Mozart Effect" conjures an image of a pregnant woman who, sporting headphones over her belly, is convinced that playing classical music to her unborn child will improve the tyke's intelligence. But is there science to back up this idea, which has spawned a cottage industry of books, CDs and videos?

A short paper published in Nature in 1993 unwittingly introduced the supposed Mozart effect to the masses. Psychologist Frances Rauscher's study involved 36 college kids who listened to either 10 minutes of a Mozart sonata in D-major, a relaxation track or silence before performing several spatial reasoning tasks. In one test—determining what a paper folded several times over and then cut might look like when unfolded—students who had listened to Mozart seemed to show significant improvement in their performance (by about eight to nine spatial IQ points).

Rauscher—whose work, unlike most scientists, is sometimes cited on the liner notes of CDs—remains puzzled as to how this narrow effect of classical music extended from a paper-folding task to general intelligence and from college students to children (and fetuses). "I think parents are very desperate to give their own children every single enhancement that they can," she surmises.

In addition to a flood of commercial products in the wake of the finding, in 1998 then-Georgia governor Zell Miller mandated that mothers of newborns in the state be given classical music CDs. And in Florida, day care centers were required to pipe symphonies through their sound systems.

A 2004 Stanford study tracked the media's coverage of Rauscher's study relative to other studies published in Nature around the same period. In the U.S.'s top 50 newspapers, her paper, titled "Musical and Spatial Task Performance," was cited 8.3 times more often than the second-most popular paper (co-authored by famed astronomer Carl Sagan).

"It seems to be a circumscribed manifestation of a widespread, older belief that has been labeled 'infant determinism,' the idea that a critical period early in development has irreversible consequences for the rest of a child's life," the researchers wrote in their analysis. "It is also anchored in older beliefs in the beneficial powers of music."

Some still argue for such musical powers. "Music has a tremendous organizing quality to the brain," notes Don Campbell, a classical musician who has written more than 20 books on music, health and education, including The Mozart Effect® and The Mozart Effect® for Children. Referencing French physician Alfred Tomatis's work in music therapy on children with dyslexia, attention-deficit disorders and autism in the mid-20th century, he believes music that's not highly emotional or overly rhythmic has a multilayered influence on the individual, from modulating mood to alleviating stress. "I know it improves our ability to be intelligent," he adds.

But in 1999 psychologist Christopher Chabris, now at Union College in Schenectady, N.Y., performed a meta-analysis on 16 studies related to the Mozart effect to survey its overall effectiveness. "The effect is only one and a half IQ points, and it's only confined to this paper-folding task," Chabris says. He notes that the improvement could simply be a result of the natural variability a person experiences between two test sittings.

Earlier this year, the Federal Ministry of Education and Research in Germany published a second review study from a cross-disciplinary team of musically inclined scientists who declared the phenomenon nonexistent. "I would simply say that there is no compelling evidence that children who listen to classical music are going to have any improvement in cognitive abilities," adds Rauscher, now an associate professor of psychology at the University of Wisconsin–Oshkosh. "It's really a myth, in my humble opinion."

Rather than passively listening to music, Rauscher advocates putting an instrument into the hands of a youngster to raise intelligence. She cites a 1997 University of California, Los Angeles, study that found, among 25,000 students, those who had spent time involved in a musical pursuit tested higher on SATs and reading proficiency exams than those with no instruction in music.

Despite its rejection by the scientific community, companies like Baby Genius continue to peddle classical music to parents of children who can purportedly listen their way to greater smarts.

Chabris says the real danger isn't in this questionable marketing, but in parents shirking roles they are evolutionarily meant to serve. "It takes away from other kinds of interaction that might be beneficial for children," such as playing with them and keeping them engaged via social activity. That is the key to a truly intelligent child, not the symphonies of a long-dead Austrian composer.