Music has been a part of humanity since existence seemingly began. From Gregorian chants and Mozart to EDM and Justin Bieber, music and the way people listen to it, has changed dramatically over time and thus shaped the society we live in.

The type of music one listens to has developed into a medium of self-expression, and has changed the way students go from class to class, study before finals, psych themselves up before a big game, and relax after a long day.

Contrary to popular belief, sound does not exist outside of the brain. Rather, air molecules vibrating in the ear bounce off one’s eardrums to give the perception of sound, and thus language and music.

According to academic journal, The Scientific American Mind, once soundwaves are registered, the auditory nerves send data to parts of the brain to locate the sound’s source, and then it sends this data to the thalamus, which decides whether to send the sound onto the cerebral cortex or stop it there, acting as a gate between the two parts of the brain.

“This gating effect enables us to control our attention selectively so that we can, for instance, pick out one particular instrument from among all the sounds being produced by an orchestra,”  Eckart O. Altenmüller wrote in The Scientific American Mind.

This is where complications in research arise. Scientists have not found a distinct path the data goes from there, but research on brain activity has shown that different hemispheres of the brain are used to process different parts of music: the left hemisphere shows predominance for processing the music’s rhythm, while the right hemisphere is used for processing the music’s different pitches and melody.

Although every individual has their own taste in music, this process remains the same from person to person. However, each person’s auditory cortexes are unique. Similar to fingerprints, music tastes will differ from one person to the next.

However, exactly how one develops a certain taste in music is much more complex than the auditory cortex. During the teenage years is when one begins to develop a certain taste in music, although there are many factors that contribute to this decision.

One factor are the friends a person will surround themselves with at this age. As an effort to fit in with their friends, a person will mold their music taste in a way that mirrors the music taste their friends have developed.

“We listen to the music they [our friends] listen to as a badge, as a way of belonging to a certain social group. That melds the music to our sense of identity,” author of This Is Your Brain on Music: The Science of a Human Obsession Daniel Levitin said in an interview with Slate Magazine.

Another factor to consider in this is one heard all too often: “you’re too emotional.”

During the teenage years, one experiences much more intense emotions, and is beginning to create his/her own self-identity. Thus, those songs listened to as a reflection of the hormonal, teen angst going on during the teenage years are going to be a more important part of establishing self-identity than a song that holds no emotional value.

This is why the lyrics of the songs people listen to are so important. Through loaded imagery and strong messages, a person will connect themselves to these lyrics with the people or events happening in their lives, such as controlling parents or a difficult break-up.

“I think that music is in and of itself a very emotional experience… the lyrics are only one part of music, and when the audible sound, rhythm, key, and lyrics are all put together, it becomes a very personal and emotional experience,” Theory of Knowledge teacher Rhonda Betzold said.

The music one listens to as a teenager stays with them throughout their life, creating an effect in the brain called musical nostalgia. It’s why parents turn the radio to the 80s station and embarrass their children with their poor rendition of “Sweet Caroline,” and why when Generation Z kids are their parent’s age, they’ll be turning the radio to the “10s station” and jamming out to “Party in the U.S.A.” by Miley Cyrus.

The brain creates memories, not just with one of the senses but all five. When one smells chocolate chip cookies baking in the oven, they may be reminded of their grandmother’s house, and when one hears “Cupid Shuffle” playing, they may be reminded of the terror that was middle school dances.

“We see ourselves through music, and many of those personal associations are made through experience. When I hear ‘In the Name of Love’ by U2, for example, I almost always picture my freshman year of college when I first heard the song. Music is the soundtrack to our lives, and we are bonded to it in a unique way,” Betzold said.

No matter the type of music one listens to, modern society is defined by a strong affinity to music. Although music may be constantly changing, the effect music has on a person will remain virtually the same.