Coarticulation and coordination in phonological development: Insights from children’s and adults’ production of complex–simplex stop contrasts in Gã

• We compared adults’ and children’s production of articulatorily challenging stops. • We focused on the Gã labio-velar (complex) vs. bilabial (simplex) stop contrasts. • Children differentiated the stop types in onset vowel formants, but adults did not. • Children’s production pattern capitalizes on a tendency for greater coarticulation. • Children show coordination limitations but strategic use of carryover coarticulation. Achieving adult-like coarticulation, which relies on precise gestural coordination, is known to be a challenging aspect of phonological development. Unique coordination challenges are posed by doubly articulated stops, typologically uncommon complex consonants that show crosslinguistic variation in their acoustic contrast with simplex (singly articulated) consonants. We examined the acoustics and development of complex–simplex stop contrasts between labio-velars (/k͡p/, /ɡ͡b/) and bilabials (/p/, /b/) in Gã (Niger-Congo, Kwa), with special attention to coarticulation with adjacent sonorants. We found that Gã adults mostly produced differences in voice onset time and closure duration to implement these contrasts, and Gã five-year-olds also produced differences in these dimensions. Crucially, however, five-year-olds also produced significant differences in onset formants, which adults did not. These findings provide evidence of age-graded variation in the implementation of complex–simplex stop contrasts in Gã, suggesting that over the course of development there may be a shift away from production of carryover coarticulatory differences toward greater reliance on durational differences. We argue that children’s initial reliance on carryover coarticulation capitalizes on a tendency toward greater consonant–vowel coarticulation as compared to adults, discussing implications for our understanding of how coarticulation develops.