Substitution errors in the production of word-initial and word-final consonant clusters.

Purpose: This study provides a comprehensive examination of substitutions that occur at Greenlee's 3rd stage of cluster development (M. Greenlee, 1974). At this stage of cluster acquisition, children are able to produce the correct number of consonants but with 1 or more of these consonants being substituted for another.

Method: Participants were 11 typically developing children ages 1;5-2;7 (years;months) who were from monolingual English-speaking homes. Consonant clusters in both word-initial and word-final position were elicited using a picture identification task.

Results: Although previous studies have suggested that most cluster substitutions can be predicted from the errors children make on the corresponding singletons, our findings indicate that almost one third of substitutions in clusters are not predictable in this way. Furthermore, the majority of unpredictable substitutions produced by the children in this study resulted in clusters in which both consonants in the cluster shared the same place and/or manner of articulation. Thus, almost 70% of unpredictable substitutions appear to be motivated by assimilation within the cluster.

Conclusion: Ease of articulation provides the most convincing explanation for within-cluster assimilation.