Jesus had his Judas. Caesar had his Brutus. And sometimes, Frances Rauscher says sadly, it seems that Mozart has his Frances Rauscher.

"Every time I listen to his music I feel like, 'Oh my, I never should have done this to this man,' " said Rauscher, a psychologist at the University of Wisconsin at Oshkosh.

What Rauscher did, six years ago, was discover what has since become known as the "Mozart effect." In a set of experiments on college students, she and two colleagues showed that 10 minutes of listening to Mozart's Sonata for Two Pianos in D Major could boost a person's score on a portion of the standard I.Q. test.

It was a small study that showed a short-lived, modest improvement in adults' performance of a specific mental task. But it wasn't long before Mozart's heavenly oeuvre got co-opted by coldly utilitarian pedagogues and parents hoping to squeeze from the Master's musical scores a few extra points on their kids' SAT scores. Then, to make matters worse, the marketing began.

One entrepreneur quickly turned the preliminary finding into a seemingly authoritative self-help book. Others released compact discs bearing extraordinary health claims. The governor of Georgia decreed that every newborn should leave the hospital with a state-purchased cassette or CD of classical music. And why wait until birth? Catalogues began offering stethoscope-like devices so pregnant women could introduce their prenatal preschoolers to Wolfgang Amadeus, in the womb.

It was against that backdrop of bloated expectations and blatant profiteering that researchers last week dropped a classical bombshell: Repeated efforts to confirm Rauscher's original results had found the Mozart effect disconcertingly elusive.

"If there is any Mozart effect at all, it's really small and has nothing to do with the specifics of Mozart's music," said Christopher Chabris, a cognitive neuroscientist at Harvard Medical School who conducted one of two related studies published in the latest issue of the scientific journal Nature. "It's smaller than originally claimed and certainly smaller than people believe."

The other study, led by Kenneth Steele, a psychologist at Appalachian State University in Boone, N.C., concluded--as several others recently have--that the sonata had no effect at all on test performance. "A requiem may therefore be in order," Steele and his colleagues wrote.

But proponents are not taking that requiem lying down. "Because some people cannot get bread to rise does not negate the existence of a 'yeast effect,' " snipped Rauscher in a reply published in Nature.

The controversy arose innocently enough with Rauscher's hypothesis that learning music, and perhaps even just listening to it, could enhance people's cognitive abilities. She and her colleagues, then at the University of California at Irvine, chose Mozart in part because his music is rich in mathematically complex motifs that seem to resonate, figuratively and perhaps even literally, with the highly organized and iterative neuronal structure of the brain.

The initial study, published in Nature in 1993, found that listening to Mozart's two-piano sonata helped college students visualize the final shape of a piece of paper as it was sequentially folded and cut in various ways. The test is a small part of the Stanford Binet Intelligence Quotient test, but the researchers made a novel (and controversial) calculation that gave the students "spatial IQ" scores of 119 after listening to the music.

That was 8 or 9 points higher than the scores achieved after either a blood pressure-lowering relaxation tape or simple silence.

Rauscher's results have been confirmed by a few others, and some studies have even hinted at broader salutary effects. John Hughes, director of clinical neurophysiology at the University of Illinois Medical Center in Chicago, conducted experiments on comatose patients whose brains were wracked by nonstop epileptic seizures. A few minutes of Mozart radically reduced the frequency of their seizures and calmed their brain wave spikes. By contrast, music by Philip Glass--whose minimalist compositions are also highly mathematical but involve much shorter periods of repetition--did nothing.

Experiments have also shown that Mozart can improve a rat's performance in a maze. "There's just too much evidence out there that there really is an effect," Hughes said. "You can't explain this effect away."

Not unless you are Harvard's Chabris. He conducted a "meta-analysis," which combined the results of all 16 published studies of the Mozart effect. Taken together, he found, there was little or no improvement in test scores among subjects who listened to Mozart.

One of those studies found that listening to a passage from a Stephen King novel enhanced performance more than did listening to Mozart--although only for those who enjoyed the story. Another, of 8,120 British schoolchildren, saw more improvement after listening to popular music. One study even found that scores improved after listening to a few minutes of Yanni, a New Age musician who, in a gimmick weirdly reminiscent of the Mozart sonata, has been known to play two electronic keyboards at once.

Chabris suspects that the Mozart effect has a simple neurophysiological explanation: "Enjoyment arousal" from pleasurable stimuli can "prime" the right hemisphere of the brain--the part of the brain that performs spatial tasks such as the paper-folding exercise.

Rauscher and her supporters fault Steele's and Chabris's techniques. And they say new studies supportive of the Mozart effect are forthcoming. Meanwhile, they contend, who would argue against plopping kids in front of a stereo to listen to some Mozart? But even this seemingly benign message has potential drawbacks, critics said.

"It does hurt if you're doing that and you think, 'Now that's it, we don't need to do the hard stuff like reading to our kids,' " said Janet DiPietro, a developmental psychologist at Johns Hopkins University School of Hygiene and Public Health.

DiPietro, who studies prenatal perception, is especially concerned about the proliferation of devices that purport to use music to aid fetal brain development. There is no evidence that prenatal exposure to music enhances child development, she said, but there is plenty of evidence that fetuses find even moderately loud music stressful when it is aimed directly at the mother's abdomen.

"They startle, they urinate, and their heart rate goes up very high," DiPietro said. "The fetal response is consistent with pain."

On one point, at least, all sides seem to agree: Too much was made of the initial findings. "We never made claims regarding general intelligence or other abstract abilities," Rauscher said. "But the next thing you know, people are saying, 'Mozart makes you smarter.' "

Ultimately, Rauscher said, the truth will emerge. "This is science at work. The process will sort it all out in the end."

If nothing else, it seems, the rise and fall of the Mozart effect may teach the public a lesson about the tentativeness of all scientific discovery. If that happens, then the incomparable composer will have made people wiser after all, if not actually smarter.