The basic idea of the theory of the "Mozart Effect" is that listening to classical Mozart symphonies/music can make a person smarter and increases IQ.
This theory has been tested and the findings, although they do not entirely match the hypothesis, do yield some interesting results. A set of research-done suggests that listening to certain specific music from Mozart may induce a short-term improvement on the performance of certain kinds of mental tasks known as "spatial-temporal reasoning," and it is suggested that early childhood exposure to classical music has beneficial effects on mental development.
Don Campbell, Inc., claims benefits far beyond improving "spatio-temporal reasoning" or "raising intelligence," defining it as "an inclusive term signifying the transformational powers of music in health, education, and well-being." Don Campbell wrote a book on the subject called "The Mozart Effect."
A 1997 book by Don Campbell, "The Mozart Effect: Tapping the Power of Music to Heal the Body, Strengthen the Mind, and Unlock the Creative Spirit," discusses the theory that listening to Mozart (especially the piano concertos) may temporarily increase a person's IQ and produce many other beneficial effects on mental function. Campbell recommends playing specifically selected classical music to infants, in the expectation that it will benefit their mental development.
After The Mozart Effect, Campbell wrote a follow-up book, "The Mozart Effect For Children," and created related products. Among these are collections of music that he states harness the Mozart effect to enhance "deep rest and rejuvenation," "intelligence and learning," and "creativity and imagination." Campbell defines the term as "an inclusive term signifying the transformational powers of music in health, education, and well-being. It represents the general use of music to reduce stress, depression, or anxiety; induce relaxation or sleep; activate the body; and improve memory or awareness. Innovative and experimental uses of music and sound can improve listening disorders, dyslexia, attention deficit disorder, autism, and other mental and physical disorders and diseases."
These theories are controversial and there are a mix of results from various studies, and while some supportive reports have been published, studies with positive results have tended to be associated with any form of music that has energetic and positive emotional qualities. Moreover, the intellectual benefits of enhanced mood and arousal are not restricted to "spatial-temporal reasoning," but extend to speed of processing and creative problem solving.
French researcher Dr. Alfred A. Tomatis in his book "Why Mozart?" speaks about the Mozart Effect. He used Mozart's music in efforts to "retrain" the ear, and believed that listening to the music presented at differing frequencies benefitted the ear--- promoting healing and the development of the brain.
Rauscher, Shaw, and Ky in 1993 investigated the "Mozart Effect" on spatial reasoning, and the results were published in "Nature." They gave research participants one of three standard tests of abstract spatial reasoning after they had experienced each of three different listening conditions: the "Sonata for Two Pianos in D major, K. 448" by Mozart, verbal relaxation instructions, and silence. They found a temporary enhancement of spatial-reasoning listening to Mozart. The study gives no statement of an increase in IQ in general because IQ was never measured although the results were popularly interpreted as an increase in general IQ.
In 1994, "New York Times" music columnist Alex Ross wrote in an article, "researchers [Rauscher and Shaw] have determined that listening to Mozart actually makes you smarter." It described one study in which three and four-year-olds who were given eight months of private piano lessons scored 30% higher on tests of spatio-temporal reasoning than control groups given computer lessons, singing lessons, and no training.
On January 13, 1998, when Zell Miller, governor of Georgia, announced that his proposed state budget would include $105,000 a year to provide every child born in Georgia with a tape or CD of classical music he stated, "No one questions that listening to music at a very early age affects the spatial-temporal reasoning that underlies math and engineering and even chess." Miller played legislators some of Beethoven's "Ode to Joy" on a tape recorder and asked "Now, don't you feel smarter already?" Miller asked Yoel Levi, music director of the Atlanta Symphony, to compile a collection of classical pieces that should be included. State representative Homer DeLoach said "I asked about the possibility of including some Charlie Daniels or something like that, but they said they thought the classical music has a greater positive impact." On efforts like Miller's budget proposal, and the press attention surrounding the effect, Rauscher has said, "I don't think it can hurt. I'm all for exposing children to wonderful cultural experiences. But I do think the money could be better spent on music education programs."
John Jenkins played Sonata K.448 to patients with epilepsy and found a decrease in epileptiform activity. According to the British Epilepsy Organization, research has suggested that apart from Mozart's "K.448" and "Piano Concerto No. 23 (K. 488)," only one other piece of music has been found to have a similar effect; a song by the Greek composer Yanni, entitled "Acroyali/Standing in Motion" (version from Yanni Live at the Acropolis performed at the Acropolis). It was determined to have the "Mozart effect", by the Journal of the Royal Society of Medicine because it was similar to Mozart's K.448 in tempo, structure, melodic and harmonic consonance and predictability.
In 1999 a major challenge was raised to the existence of the Mozart Effect by two teams of researchers. In a pair of papers published together under the title "Prelude or Requiem for the Mozart Effect" Chabris reported a meta-analysis suggesting that "any cognitive enhancement is SMALL and does not reflect any change in IQ or reasoning ability 'in general,' but instead derives entirely from performance on one specific type of cognitive task and has a simple neuropsychological explanation" called "enjoyment arousal." He cites a study that found that "listening either to Mozart or to a passage from a Stephen King story enhanced subjects' performance in paper folding and cutting (one of the tests frequently employed by Rauscher and Shaw) but only for those who enjoyed what they heard." Steele et. al. found that "listening to Mozart produced a 3-point increase relative(compared) to silence in one experiment." In another study, the effect was replicated with the original Mozart music, but the effect was eliminated when the tempo was slowed down and major chords were replaced by minor chords. The "neural resonance" theory of Rauscher and colleagues contends that Mozart's music primes the neural pathways of spatial reasoning. Popular presentations of the "Mozart effect", including Alex Ross's comment that "listening to Mozart actually makes you smarter" and Zell Miller's "don't you feel smarter" query to the Georgia legislature, almost always tie it to "intelligence."
Another meta-analysis by Pietschnig, Voracek, and Formann in 2010 combined results of 39 studies to answer the question as to whether or not the Mozart Effect exists. They concluded that there isn't a lot of evidence to support the Mozart Effect, as shown by the small effect sizes, however, the most striking finding in this analysis is the significantly larger effects published in studies affiliated with Rauscher or Rideout--- with effect sizes more than three times higher.
Research on animals suggests that exposure to even rats improves their maze learning abilities. A German sewage treatment plant plays Mozart music to break down the waste faster, reports the UK Guardian. Anton Stucki, chief operator of the Treuenbrietzen plant was quoted as saying, "We think the secret is in the vibrations of the music, which penetrate everything—including the water, the sewage and the cells."
There are a variety of ideas on this topic, and the results are controversial. We can see a list of potential positive results, and not a list of negatives, so overall, it wouldn't hurt to give it a try and expose small children to such forms of classical music just-in-case there could be some benefit to it.