When picking songs for a playlist, you may choose bluegrass over big band, or death metal over dubstep — but the assumption that all of us enjoysome form of music was accepted as part of human nature. New research, however, may change our tune entirely.

Researchers at the University of Barcelona recently divided college-aged participants into three small groups based on how sensitive they reported being to music. After confirming that none of the volunteers were tone deaf, they were asked to participate in two activities.

The first was to listen to a range of music deemed enjoyable by other college students. During this, the participants in each group had their heart rate measured, as well as their skin response. While most of the participants had an emotional reaction to music, evidenced by sweating more, getting chills or having an increased heart rate, a small segment of the population didn’t react at all. They had no real response to the music.

The researchers asked this small group whether they could identify the emotions conveyed in the different songs, which they could — confirming that they understood the music, they were just indifferent to it.

Next, the volunteers received a routine psychological test where they could gain or lose real money by playing a game. This time, both the music lovers and those indifferent to music showed physiological responses. From this, the researchers concluded that there was nothing wrong with the brains of participants who didn’t respond emotionally to music; their indifferenceonly seems to concern music.

The researchers estimate 1 to 5 percent of people don’t receive pleasure from music. From here, it may be possible to understand what makes music so pleasurable for the rest of us — and how and why our reward networks respond the way they do.