Evaluating mechanisms underlying nonspeech context effects in coarticulatory compensation
Navin Viswanathan · The Journal of the Acoustical Society of America · 2018
Human speech listeners overcome variability in the speech signal due to different speakers, rates, phonetic contexts etc., by demonstrating context-appropriate perceptual shifts. From a general auditory perspective, perceptual systems heighten contrastive spectral and temporal properties of the acoustic signal to help listeners cope with variability (Diehl et al., 2004). In this study, I focus on a spectral contrast account of perceptual coarticulatory compensation and evaluate the claim that listeners cope with coarticulation by tracking spectral averages across multiple segments (Holt, 2005) while ignoring spectral variability (Holt, 2006). In Experiment 1, using tone analogue contexts (Lotto & Kluender, 1998) I created multi-tone contexts such that the global spectral average of each trial was pit against the frequency of the final tone that immediately preceded the target speech. Interestingly, nonspeech context effects were determined by the frequency of the final tone rather than the global trial average. A follow up experiment 2 indicated that contexts with identical overall spectral averages can produce different effects on following speech depending on the final tone. These findings taken together call into question the assumed mechanisms underlying spectral contrast.