Everyone dislikes some kind of music, but are there people out there who don't respond to music at all?
Apparently, yes, and they weren't lying when they said so, according to a study published online in Current Biology.
A team of researchers from Spain and Canada was trying to develop an accurate questionnaire to gauge people's sense of reward from music when they found roughly 5 per cent of their study subjects reported getting no pleasure at all from music.
So they followed up by testing 30 subjects, grouped by their relative affinity for music. The bottom group, which expressed the least pleasure in music, also exhibited the least change in heart rate or skin conductivity - which are proxy measures of emotional response - when listening even to pieces they chose.
"They were not just saying so, but the physiological responses were in accord with what they were saying," said the study's lead author, cognitive psychologist Josep Marco Pallares, of the Bellvitge Biomedical Research Institute in Barcelona.
There are people who can't process music well - about 4 per cent of the population has amusia. Others, particularly those with depressive disorders and neurodegenerative diseases, suffer from general anhedonia - a pronounced deficit in experiencing pleasure from widely different stimuli.
But is there a separate musical anhedonia? The study suggests so. None of the participants showed signs of general anhedonia, nor did they exhibit significant differences in their sensitivity to rewards, the study revealed.
All did well at categorising musical passages as happy, sad, scary or peaceful, according to the study. They reported no differences in their levels of pleasure with stimuli other than music.
The study suggests not only that musical enjoyment is not as universal as commonly assumed, but also that the brain's pleasure response may be fragmented.
"In general, it's thought that there is a continuum in the degree of pleasure you get from rewards," Marco said. "This is not completely true. There are differences, but this kind of activity depends on the type of stimuli.
"There are different kinds of stimuli which may be more effective in activating the reward system, and some that might not be effective at all."
Marco said the results could help the team refine musical therapies for stroke victims, which sparked their interest in the brain's reward response to tunes. But it could be applied to other therapies, he said.
Anhedonia is a key component of major depressive disorders, and is common among those with Parkinson's disease.