Speech and language production at age 2: evidence for tradeoffs between linguistic and phonetic processing

The purpose of this study was to explore how 2-year-old children manage the relationship between phonetic production and production of word combinations in their spontaneous speech. The subjects were 5 normally developing 2-year-olds who were participants in an ongoing longitudinal study of speech and language acquisition. Three measures were used to estimate phonetic production skills in the children's spontaneous speech samples. These included a measure of the accuracy of consonant production (Percentage of Consonants Correct), and two estimators of phonetic complexity (phonetic products for utterance and word length units). Regression analyses were used to determine the relationship between complexity of word combinations, as measured by length of utterance in morphemes and a propositional complexity analysis, and utilization of phonetic production skills. The results revealed modest tradeoffs between complexity of word combinations and accuracy of consonant production for 2 of the 5 children. The results also showed tradeoffs between complexity of word combinations and phonetic complexity of individual lexical items (phonetic product for words) for 4 of the 5 children. As the complexity of these 4 children's multiword combinations increased, the phonetic complexity of individual lexical items decreased. These results are consistent with synergistic theories of language acquisition and language processing that emphasize dynamic tradeoffs in interactions among language processing levels in a limited capacity production system.