Do mice succumb to Mozart?
and World Science staff
The idea is at least as controversial today as it was when a famous 1993 study suggested it: listening to Mozart makes you smarter, at least temporarily.
Some researchers say the notion is completely debunked by now, though that hasn’t stopped a cottage industry of Mozart CDs for children from booming.
Into this mess, a set of even more startling findings has crashed through the door. Few if any people would claim that rodents appreciate classical music, yet studies from three laboratories have found this much: Mozart does something for them.
The research found that the music improves maze performance in the animals. Some of the findings also pointed to accompanying biochemical changes.
Proponents of the so-called “Mozart effect” are flushed with confidence, noting that the agreement of three “independent” studies starts to approach something that could be called rock-solid evidence. But with skeptics continuing to dispute the results, the only certainty is that the debate isn’t over.
Doubters point out that among other things, rats and mice can’t even hear much of Mozart’s music. The pitches are too low for them.
“It’s important to approach these studies with a critical eye and not be dazzled by the big claims being made,” wrote Harvard University’s Christopher Chabris, who conducted a study disputing the “Mozart-effect” findings in humans in 1999.
The original 1993 study with humans reported that listening to 10 minutes of Mozart’s music increased the “spatial reasoning” ability of college students on tests for the next 10 to 15 minutes.
Attempts to replicate the finding gave mixed results. Chabris analyzed 16 studies and in 1999 concluded there was no “Mozart effect,” except possibly an improvement on one test involving ability to transform visual images, with even that result falling short of statistical significance.
Chabris attributed any effect to “enjoyment arousal” in his analysis, published in the Aug. 26, 1999 issue of Nature, the same research journal that published the original finding. His work led to responses and counter-responses, along with contentions that the “Mozart effect” might last longer than originally reported.
As the debate raged, seeds of an even stranger finding had begun to sprout.
In the July 1998 issue of the journal Neurological Research, Frances Rauscher of the University of Wisconsin, Oshkosh, and colleagues reported results of a study in which rats were exposed to Mozart while in the womb and for 60 days after birth.
The rats completed a maze faster and with fewer errors than rats exposed instead to simpler music, silence, or a static-like noise, according to Rauscher, who had led the original study in humans.
Chabris and others disputed that report, too. But two more studies with similar results have appeared in scientific journals in recent months: one in the December 2005 issue of Neurological Research and the other in the latest issue of Behavioural Brain Research, dated May 15.
Both were designed to some extent to replicate Rauscher’s finding, with some key differences. The first omitted the in-uterus music exposure. The second studied mice instead of rats. Both found that the Mozart-exposed rodents made fewer errors on maze tests, though only the first found that they also completed the tests faster.
“Continuous exposure to music during the perinatal (before-and-after birth) period enhances learning performance in mice as adults,” wrote the authors of the second study, Sachiko Chikahisa and colleagues at Tokushima University in Tokushima, Japan.
Chikahisa’s group also found that the improved learning was associated in increased levels in the brain of a molecule associated with “neural plasticity”—the ability of brain cells to change their connections, believed to be important for learning. The molecule, a protein, is called TrkB.
Thus, “at this time I would say there are two independent replications of my original” finding, wrote Rauscher in an email.
But Kenneth M. Steele of Appalachian State University in Boone, N.C., a past critic of Mozart-effect findings, said some of the new findings also appear flawed. He said Chikahisa’s paper exhibits some wrong statistical techniques and some of the numbers presented suggest possible selective use of data.
Also, the data show the Mozart mice were on average “a little heavier than the other groups. This may indicate greater maturity,” Steele wrote in an email. Moreover, “this study suffers from the same flaw as the Rauscher et al. study: lack of random assignment. The mothers were randomly assigned to a group. But the assignment of the offspring was determined by their mother.”
While Steele said he hadn’t read the study in Neurological Research in detail, he suggested its authors might not have been objective, having supported the Mozart effect in the past.
But perhaps the strongest objection, he said, is that rats can’t even hear most of the notes in the Mozart music played in the studies, and mice can hear none of them. Both animals’ hearing range only covers much higher pitches than human hearing does. Mice and rats are also born deaf, Steele added.
But Chikahisa and colleagues argued that mice can hear some of the higher pitches in the music, and that “there are some studies that music influences behavior, brain function, immunity and blood pressure in rodents.”
Tokushima University’s Hiroyoshi Sei, one of the co-authors, said in an interview that mice may feel vibrations even if they don’t hear them.
Peter Aoun and colleagues at the MIND Institute of Costa Mesa, Calif., authors of the Neurological Research study, wrote that rodents needn’t enjoy the music for it to have an effect. Some researchers have argued that certain music may benefit the brain by simply by stimulating natural patterns of brain activity. Sei said that to clarify such questions, he’s testing the effect of music on totally deaf mice.
He’s not sure, he added, what about the music may have influenced the rodents. But “it definitely something affects something in their behavior,” he said.
* * *
Send us a comment
on this story, or send
it to a friend