Simultaneous acquisition of multiple auditory-motor transformations reveals suprasyllabic motor planning in speech production.

Abstract

Motor planning forms a critical bridge between psycholinguistic and motoric models of word production. While syllables are often considered the core speech motor planning unit, growing evidence hints at suprasyllabic planning that may correspond to words, but firm experimental support is still lacking. We use differential adaptation to altered auditory feedback to provide novel, straightforward evidence for word-level planning. By introducing opposing perturbations to shared segmental content in near real time during speaking (e.g., raising the first vowel formant of "ped" in "pedigree" but lowering it in "pedicure," so speakers hear something akin to "padigree" and "pidicure"), we assess whether participants can use the larger word context to separately oppose the two perturbations (i.e., by producing "pidigree" and "padicure"). Critically, limb control research shows that such differential learning is possible only when the shared movement forms part of distinct motor plans, allowing a straightforward assay of the scope of planning in multisyllabic words. We found differential adaptation in multisyllabic words but of smaller size relative to monosyllabic words. Our results strongly suggest that speech relies on an interactive motor planning process encompassing both syllables and words. (PsycInfo Database Record (c) 2025 APA, all rights reserved).