Why are repeated words produced with reduced durations? Evidence from inner speech and homophone production

Acoustic reduction for repeated words could be the result of articulation and motor practice (Lam & Watson, 2014), facilitated production (Gahl, Yao, & Johnson, 2012; Kahn & Arnold, 2015), or audience design and shared common ground (Galati & Brennan, 2010). We sought to narrow down what kind of facilitation leads to repetition reduction. Repetition could, in principle, facilitate production on a conceptual, lexical, phonological, articulatory, or acoustic level (Kahn & Arnold, 2015). We compared the durations of the second utterance of a target word when the initial production was aloud or silent. The silent presentation either involved unmouthed or mouthed inner speech. Overt production, unmouthed and mouthed inner speech all led to reduction in target word onsets, but target word durations were only shortened when a word was initially said aloud. In an additional experiment, we found that prior naming of a homophone of the target word also led to duration reduction. The results suggest that repetition reduction occurs when there is a recently experienced auditory memory of the item. We propose that duration may be controlled in part by auditory feedback during production, the use of which can be primed by recent auditory experience.