In this article, the author discusses the "Mozart effect," which is the belief that listening to classical music--such as Mozart's compositions--can lead to long-term improvement in brain function. The author argues that Mozart effect is just a common case of correlation, and not causation.
The Mozart effect dictates that people who happen to listen to classical music happen to be more intelligent, but studies tell a different story. Studies show that passively listening to music is has little to no effect at all. The author states that the measurable increase in brain function--like solving mathematical problems--are caused by the positive mood set by listening to music in general. She states, "positive mood, in turn, increases focus and attention, which improves performance on many tests of mental sharpness." Instead of listening to music, studies show, "learning to make music changes the brain and boosts broad academic performance."
This Mozart effect can be the result of the environment and the opportunities in which the kids are given. It could be that babies or children who listen to classical music happen to grow up in households where the parents/guardians rate education very highly. With this in mind, these children are most likely to learn how to play music because learning an instrument is part of a healthy education; learning how to compose/produce music is the real cause of brain development.