We investigated whether the categorical perception (CP) of speech might also provide a mechanism that aids its perception in noise. We varied signal-to-noise ratio (SNR) [clear, 0 dB, −5 dB] while listeners classified an acoustic-phonetic continuum (/u/ to /a/). Noise-related changes in behavioral categorization were only observed at the lowest SNR. Event-related brain potentials (ERPs) differentiated category vs. category-ambiguous speech by the P2 wave (˜180-320 ms). Paralleling behavior, neural responses to speech with clear phonetic status (i.e., continuum endpoints) were robust to noise down to −5 dB SNR, whereas responses to ambiguous tokens declined with decreasing SNR. Results demonstrate that phonetic speech representations are more resistant to degradation than corresponding acoustic representations. Findings suggest the mere process of binning speech sounds into categories provides a robust mechanism to aid figure-ground speech perception by fortifying abstract categories from the acoustic signal and making the speech code more resistant to external interferences.

35 EMAIL: gmbdlman@memphis.edu 2 36 ABSTRACT 37 We investigated whether the categorical perception (CP) of speech might also provide a mechanism that 38 aids its perception in noise. We varied signal-to-noise ratio (SNR) [clear, 0 dB, -5 dB] while listeners 39 classified an acoustic-phonetic continuum (/u/ to /a/). Noise-related changes in behavioral categorization 40 were only observed at the lowest SNR. Event-related brain potentials (ERPs) differentiated phonetic vs. 41 non-phonetic (category ambiguous) speech by the P2 wave (~180-320 ms). Paralleling behavior, neural 42 responses to speech with clear phonetic status (i.e., continuum endpoints) were largely invariant to noise, 43 whereas responses to ambiguous tokens declined with decreasing SNR. Results demonstrate that phonetic 44 speech representations are more resistant to degradation than corresponding acoustic representations. 45Findings suggest the mere process of binning speech sounds into categories provides a robust mechanism 46 to aid perception at the "cocktail party" by fortifying abstract categories from the acoustic signal and 47 making the speech code more resistant to external interferences.48 49 50 51