Late talking toddlers : relating early phonological development to later language advance

Background. Expressive Late talkers are identified as children with an unusually small productive vocabulary for their age, in the absence of any other known neurological, sensory or cognitive deficit. Their lexical delay has been found to be associated withphonetic delay. Aims. The two primary goals of this study are (1) to provide intensive analyses of phonetic and phonological characteristics of late talkers (LTs) at the end of the single word period as a basis for comparing their speech with that of typically developing children (TDs), not at the same age but at the same developmental point; (2) to compare the relative phonological, lexical, morphological and syntactic advance of the same two groups 14 months later, based on analysis of spontaneous language use, and to relate this advance to phonetic and phonological resources at the earlier measurement point. Methods and procedures. Time 1 analyses included assessment of volubility, size of consonant inventory, percent consonants correct and extent of consonant variegation and of the use of selected prosodic patterns or ‘templates’. Time 2 analyses assessed advance in phonology (percent consonants correct), lexicon (diversity of verb and function word types), morphology (provision of obligatory morphemes) and syntax (MLU, IPSyn). Outcomes and results. Although three groups differing in age at achieving Time 1 lexical criterion were identified (TDs, LTs and ‘transitional’ LTs or TLTs), there is little evidence of group differences in other measures of linguistic advance at either sampling point, when the groups are compared at the same lexical level. Exploratory statistical analyses using Canonical Correlations revealed that a combination of high age at Time 1,small consonant inventory and low phonetic variegation are strong predictors of low accuracy in consonant use and relatively poor lexicon, morphology and syntax at Time 2, while dependence on a limited set of phonological patterns at Time 1 was significantly correlated more specifically with slower morphological advance at Time 2. Conclusions and implications. The study found that, once the groups are equated for lexical level, the linguistic skills of LTs as a group are not distinguishable from those of TDs in either the early period of phonological development or the year following the endof the single-word period. Nevertheless, based on the relation of Time 1 to Time 2 measures within individuals, the study also demonstrates that phonetic and phonological knowledge and skills constitute a key foundation for later linguistic advance, as regards grammar as well as phonology