Musical anhedonia, timbre, and the rewards of music listening.

Pleasure in music has been linked to predictive coding of melodic and rhythmic patterns, subserved by connectivity between regions in the brain's auditory and reward networks. Specific musical anhedonics derive little pleasure from music and have altered auditory-reward connectivity, but no difficulties with music perception abilities and no generalized physical anhedonia. Recent research suggests that specific musical anhedonics experience pleasure in nonmusical sounds, suggesting that the implicated brain pathways may be specific to music reward. However, this work used sounds with clear real-world sources (e.g., babies laughing, crowds cheering), so positive hedonic responses could be based on the referents of these sounds rather than the sounds themselves. We presented specific musical anhedonics and matched controls with isolated short pleasing and displeasing synthesized sounds of varying timbres with no clear real-world referents. While the two groups found displeasing sounds equally displeasing, the musical anhedonics gave substantially lower pleasure ratings to the pleasing sounds, indicating that their sonic anhedonia is not limited to musical rhythms and melodies. Furthermore, across a large sample of participants, mean pleasure ratings for pleasing synthesized sounds predicted significant and similar variance in six dimensions of musical reward considered to be relatively independent, suggesting that pleasure in sonic timbres play a role in eliciting reward-related responses to music. We replicate the earlier findings of preserved pleasure ratings for semantically referential sounds in musical anhedonics and find that pleasure ratings of semantic referents, when presented without sounds, correlated with ratings for the sounds themselves. This association was stronger in musical anhedonics than in controls, suggesting the use of semantic knowledge as a compensatory mechanism for affective sound processing. Our results indicate that specific musical anhedonia is not entirely specific to melodic and rhythmic processing, and suggest that timbre merits further research as a source of pleasure in music.