Novel acoustic measures of coarticulation reveal morphological planning in child speech

How do children plan and represent morphologically complex words throughout childhood? We employed coarticulation as a lexical planning metric in speakers of South Bolivian Quechua (SBQ), a highly agglutinating language with over 200 suffixes. 10 adult and 50 child (age 5–10) SBQ speakers completed a real word repetition task. V-C coarticulation was measured in the sequences [ap] and [am] in two contexts: within root morphemes (e.g., papa ‘potato’) or at morpheme boundaries (e.g., llama-pi ‘llama-locative’). Acoustic analysis of coarticulation using formant tracking is complicated in child speech because of children’s short vocal tracts and high f0. Following Gerosa et al. (in IEEE International Conference on Acoustics Speed and Signal Processing Proceedings (2006), Vol. 1, pp. 393–396), we quantified the degree and time course of coarticulation in Mel-frequency spectral differences. Results show that adults distinguished acoustically between phones more at morpheme boundaries than within morphemes, while children did not distinguish. This conclusion is further evidence that adults decompose words and plan them online. The lack of distinction in child speech, however, suggests that children may be accessing these complex words holistically, even in this highly agglutinating language.How do children plan and represent morphologically complex words throughout childhood? We employed coarticulation as a lexical planning metric in speakers of South Bolivian Quechua (SBQ), a highly agglutinating language with over 200 suffixes. 10 adult and 50 child (age 5–10) SBQ speakers completed a real word repetition task. V-C coarticulation was measured in the sequences [ap] and [am] in two contexts: within root morphemes (e.g., papa ‘potato’) or at morpheme boundaries (e.g., llama-pi ‘llama-locative’). Acoustic analysis of coarticulation using formant tracking is complicated in child speech because of children’s short vocal tracts and high f0. Following Gerosa et al. (in IEEE International Conference on Acoustics Speed and Signal Processing Proceedings (2006), Vol. 1, pp. 393–396), we quantified the degree and time course of coarticulation in Mel-frequency spectral differences. Results show that adults distinguished acoustically between phones more at morpheme boundaries than within morphemes, while...