Perceived naturalness of typical disfluent speech and speech of adults who stutter

Disfluencies in spontaneous speech have been shown to be sensitive to the syntactic constituency (Levelt, 1989): production is restarted at the boundary nearest to the point of interruption. While there is a production-internal account of constituency structure in the speech of both adults who stutter (AWS) and typical speakers (AWNS), there is no evidence of constituency realization in the perceptional account of disfluent speech. The current study explores whether the constituency structure contributes to the perception of disfluent speech of AWS and AWNS. More specifically, the study investigates whether syntactic constituents are a cohesive unit of perception and whether altering the constituency structure impacts the perceived naturalness of disfluent speech. The participants rated the samples of disfluencies produced by AWS and AWNS for naturalness. The stimuli were presented in their original form as well as in a form with an artificially altered disfluency position. The results indicate that the location of the repetition disfluency is one of the correlates of speech naturalness, both in stuttered and typical speech. At the same time, speech naturalness ratings are minimally influenced by the type of speaker, suggesting that stuttering and typical disfluencies follow similar perceptual patterns.