The truth, however, probably has more to do with youth than it does music. In holding on to the musical preferences forged for us in our "formative years," each of us may have a lot in common with mice in a recent study published in the Proceedings of the National Academy of Sciences of the United States. In this study, researchers tried to get mice to overcome their natural instinct to choose quiet places to nest in rather than noisy places. Given a choice – free of any prior conditioning – mice tend to always choose the quieter environments. They'll explore the entire area available to them for nesting, but then almost always group in the quietest possible corner.
They'll do this, that is, unless they have been exposed to music during their "teenage years." For mice, that's similar to what it is in humans – between the ages of 15 and 24 – although in the case of the mice we're talking days, not years.

Serenading the mice
The neurobiologists conducting this experiment built a large, open area for the mice to explore and inhabit…sort of an upscale mouse condo. The mouse subjects were divided into two groups, each consisting of equal numbers of adult (60 days old or older) and adolescent (15 days old) mice. The control group (no music) was allowed to roam the environment and select their nesting grounds as they wanted; they reacted as expected, preferring the quieter areas. 

But then they installed tiny mouse-sized music systems in a number of areas, and played for the other group of mice a series of musical serenades for three hours at a time, on a loop. The music selections were two symphonies by Beethoven (the 1st and the 9th), and a bossa nova classic performed by Antonio Carlos Jobim. The objective was to see whether they could condition the mice to prefer the mousey music rooms to the quiet rooms, and thus overcome their instinctual desire to gravitate to the quieter areas.
In the adult mice, no change was seen in their nesting behavior, even after conditioning; they still preferred the quieter areas. But the adolescent mice, once exposed to music, grouped in the more noisy areas rather than the quiet ones. No differences were perceived between the mice listening primarily to Beethoven and those listening to bossa nova. It seemed to be just the exposure to music period during that formative period of their youth that had changed their behavior. 

What does all of this mean?
Well, not being a mouse it's difficult to say for sure, but the researchers theorized that there is a specific period of mental development during which the brain is imprinted or "set" by its aural environment. During adolescence certain areas of the brain have a plasticity that is lost in later years. During that period of time, stimuli from their environment (including sounds) cause changes that are expressed in behavioral patterns later in life. 

To test the theory, the researchers gave a compound called valproic acid – known to increase plasticity in the brain and thus make it more receptive to new neural patterns – to the adult mice, to see if they could create the same musical conditioning they saw in the younger mice. It worked. The adult mice "on" valproic acid now listened to the music, and developed a similar appreciation for it as the adolescent mice. Afterwards, they too built their nests in the noisier areas rather than the quieter areas, something they would never do normally. 

The findings of this study, although fascinating, merely point in the direction of future research. More work has to be done on scanning the brains of the conditioned mice to see which areas have been altered by exposure to music. Discovering this may lead to information that will prove applicable to humans, and things that can trigger renewed brain plasticity in adult humans as it did in the adult mice. This could help in the development of therapies or drugs that could reverse mental imbalances created as a result of environmental conditioning during the formative years of childhood and adolescence. 

I wish the researchers well with this continued research, although I might suggest using different music during their next tests. My bet is that both the adult and the adolescent mice will prefer silence after listening to Barry Manilow, and that both the adult and the adolescent mice will prefer the musical areas after listening to Jimi Hendrix. Some music really is better, after all.