For most people, the mere suggestion that a favorite song fails to evoke an emotional response in another human being sounds preposterous. Sure, that person might not like that song as much as you do, but they'll definitely feel something — right?

Not necessarily, says Josep Marco-Pallerés, a cognitive neuroscientist at the University of Barcelona and lead author of a new study that explores why some people feel indifferent to music. "Music isn't rewarding for them, even though other kinds of rewards, like money, are," he says. "It just doesn't affect them."

To find out why, researchers recruited 30 university students, each of whom had been identified as very sensitive to music, moderately sensitive, or not sensitive at all thanks to a questionnaire. Researchers also made sure that the study's participants weren't depressed, tone-deaf, hearing-impaired, or otherwise unable to understand music — all factors that would have dampened their pleasure response.

Then, researchers monitored the student's heart rates and sweat levels during listening sessions involving familiar pieces of music (previous studies have shown that people react more strongly to music they know). "We asked them to bring music from home that they like," Marco-Pallerés recalls, "and most of them had problems doing that." Those who were indifferent to music either ended up bringing a smaller number of recordings — some didn't own music at all — or had to borrow music from a family member.

The study's results, published today in Current Biology, are surprising. Although these participants were perfectly capable of perceiving when a tune was sad or happy, they didn't show physical or emotional reaction. They didn't shiver if a singer hit a high note, and their heart rate didn't increase with each crescendo. But when asked to play a game involving a monetary reward, those who were indifferent to music reacted just like everyone else: the thought of winning even a small amount of money was enough to make their hearts race. The results were unchanged a year later, when 26 of the students took the test again.

But we shouldn't mistake an indifference to music for dislike, Marco-Pallarés says. When students were asked to describe their affinity for music on a scale of one to ten, for example, those who were indifferent usually answered with the number five — the mathematical equivalent of a shrug.

Researchers even have a name for the condition: "specific musical anhedonia." The term anhedonia is used by psychologists to describe a person's inability to derive pleasure from activities that most find enjoyable. But as the monetary-reward experiment indicates, this specific anhedonia only affects music perception. "Now that we know that there are people with specific musical anhedonia," Marco-Pallerés says, "we want to know the neural bases that might explain [it]." The research team plans to conduct a new experiment using functional magnetic resonance imaging (fMRI) to study how the brain's reward system differs in these people.

This is first experiment to demonstrate that anhedonia can be specific to a single form of reward, so many questions remain unanswered. There might be other forms of specific anhedonia that we don't know about yet, Marco-Pallerés says. But the fact that the first form to be identified is related to music is interesting in and of itself, he says, because from an evolutionary standpoint, it's hard to explain why we like music in the first place. "Music doesn't give us access to biologically relevant advantages," he says, the way food or money does. "The emotions are the key point in this reward."

So, from a survival standpoint, there's no disadvantage to being indifferent to music. As Marco-Pallerés puts it, you just end up with "people who don't understand why anyone would pay to go to a concert."