Adult speakers readily decompose morphologically-complex words into their component parts. Overgeneralizations in children’s early speech (e.g. goed) demonstrate that they must share in this ability. However, acoustic evidence from child speech suggests that children do not always break words down, instead storing language in more holistic chunks such as syllables or even entire words.

How are morphologically-complex forms represented throughout childhood? To answer this, we measured coarticulation within and between morphemes in adult and child (age 5-10) South Bolivian Quechua speakers. Coarticulation was quantified as the difference between the averaged Mel frequency cepstral coefficient vectors of the adjacent phones. Experiment 1 replicates known coarticulatory findings from the literature, demonstrating the validity of the MFCC measurement for calculating adjacent coarticulation. Experiment 2 then measures coarticulation between a single biphone sequence, [ap], in two environments: 1) within morphemes and 2) across morpheme boundaries. Results show that adult speakers coarticulated less across morpheme boundaries than within root morphemes. This is further evidence that adults decompose complex words. Children, however, coarticulated equally across and within morphemes. This suggests that the child speakers store inflected words more holistically than adults, even in this highlyagglutinating language.