Song familiarity relies on evidence accumulation

Familiarity judgements are thought to involve evidence accumulation, a decision-making process in which information is gathered over time until a threshold is reached. Previous work has identified a scalp-recorded signature of evidence accumulation called the central-parietal positivity (CPP). We built on this previous work and recorded electroencephalography (EEG) while participants listened to several melodies, instructing participants to respond as soon as the song felt familiar. A prominent CPP was noted, time-locked to decisions. We then used linear regression to unmix overlapping neural responses and observed a stimulus-locked indicator of evidence accumulation that increased in amplitude just prior to a familiarity decision. This result suggests that song familiarity relies on evidence accumulation, with individual notes in a familiar song acting as "evidence".