Relationships between measures of levels of phonological knowledge and outcome measures of speech and language skills

Phonological knowledge is a broad construct, referring, in part, to an understanding of how sounds and sound patterns relate to word forms and language. The study discussed in this dissertation was designed to examine the performance of younger and older typically developing children on tasks thought to measure different aspects of phonological knowledge, using the hierarchical model of Pierrehumbert (2003) as a guide for task design. The outcomes of these tasks were used to identify relationships between early phonological knowledge and speech production and language skills. Twenty nine children, comprising 15 younger (4:0 to 5:11) and 14 older (ages 6:0 to 7:11) children, completed a within- and between-category discrimination task, a nonword repetition task, a nonword discrimination task, and a battery of standardized speech and language tests. The discrimination tasks were presented using a change/no change procedure (Sussman & Carney, 1989). Performance was summarized with D-Prime (d') scores. As in previous research, the older children discriminated sounds more accurately than younger children, and repeated nonwords more accurately, which suggests a developmental progression in the acquisition of these skills. A path analysis suggests that there is little direct effect of lower-level categorical knowledge on the higher-level skill of nonword repetition; rather, the contribution of categorical knowledge is mediated by its relationship to nonword perception, which, in turn, influences both receptive vocabulary and nonword repetition. The results of this study support models postulating a hierarchical structure of phonological knowledge, with differential contributions of each level of knowledge to outcome measures of speech and language skill.