Representations of personally familiar voices are better resolved in the brain.

The human voice is highly flexible, allowing for diverse expression during communication, but presents perceptual challenges through large acoustic variability. The ability to recognize an individual person's voice depends on the listener's ability to overcome this within-speaker variability to extract a single identity percept. Previous work has found that this process is greatly assisted by familiarity, with evidence suggesting that more extensive and varied exposure to a voice is associated with the formation of a more robust mental representation of it. Here, we used functional magnetic resonance imaging (fMRI) with representational similarity analysis to characterize how personal familiarity with a voice is reflected in neural representations. We measured and compared brain responses with voices of differing familiarity-a personally familiar voice, a voice familiarized through lab training, and a new (untrained) voice-while listeners identified these voices from naturally varying, spontaneous speech clips. Personally familiar voices elicited brain response patterns in voice-, face-, and person-selective corticesthat showed higher within- and between-speaker dissimilarity, compared with lower-familiarity lab-trained and untrained voices. These findings indicated that representations for the sounds of personally familiar voices are better resolved from each other in the brain, and they align with other research reporting intelligibility advantages for speech produced by familiar talkers. Overall, our findings suggest that extensive and varied exposure to personally familiar voices results in the development of finer-grained representations of those voices, which cannot be achieved via short-term lab training.