The impact of clear speech modifications on perceived tempo of rate-matched English utterances

This study investigates the impact of clear speech modifications on perceived tempo, when listeners judge utterances that differ in speaking mode but are matched for articulation rate. Previous research motivates competing hypotheses: clear stimuli should sound faster if listeners’ judgements are informed by differences in rate of spectral change; or slower if listeners are informed by knowledge of production patterns and differences in intelligibility; or the same in tempo if listeners weigh the available cues equally. This study addresses these hypotheses in three experiments using paired clear and normal productions of English sentences, with the clear productions manipulated to match their articulation rate to that of the normal productions. Experiment 1 assessed listeners’ ability to separate the parameters of tempo and speaking mode when exposed to these pairs. Experiment 2 assessed the perceived direction of tempo difference in the same pairs. Experiment 3 expanded on Experiment 2 by adding two dimensions of variability: productions of different sentences were paired, and articulation rate was further manipulated to yield slow, mid, and fast pairs. Across the experiments, the hypothesis that rate-matched clear stimuli should sound faster than normal ones finds the strongest support. Implications for our understanding of tempo perception are discussed.