Date of Degree
PhD (Doctor of Philosophy)
Speech Pathology and Audiology
Karla K. McGregor
Children with cochlear implants (CIs) typically have smaller lexicons in relation to their same-age hearing peers. There is also evidence that children with CIs show slower rates of vocabulary growth compared to hearing children. To understand why children with CIs have smaller vocabularies, we proposed to investigate their word learning process and determine how it compares to children with normal hearing. The present study explores multiple aspects of word learning - acquisition, extension, and retention - to better inform us about the real-world process of lexical acquisition in children with CIs.
We evaluated 24 children with cochlear implants, 24 children with normal hearing matched by chronological age, and 23 children with normal hearing who were matched by vocabulary size. Participants were trained and tested on a word learning task that incorporated fast mapping, word extension, and word retention over two days. We also administered a battery of tests that included measures of receptive vocabulary and speech perception skills to determine which variables might be significant predictors of fast mapping and word retention.
Children with CIs performed more poorly on word learning measures compared to their age-mates, but similarly to their vocabulary-mates. These findings indicate that children with CIs experience a reduced ability to initially form word-referent pairs, as well as extend and retain these pairs over time, in relation to their same-age hearing peers. Additionally, hearing age-mates and vocabulary-mates showed enhancement in their production of novel words over time, while the CI group maintained performance. Thus, children with CIs may not take the same route in learning new words as typically-developing children. These results could help explain, in part, why this population consistently demonstrates slower rates of vocabulary learning over time. Furthermore, we expected that speech perception and vocabulary size would relate to variations in fast mapping, as well as word retention. Neither of these variables proved to be significant predictors of fast mapping, but they were highly significant for word retention. Based on these findings, we may conclude that the factors that account for acquiring that first link between a word and its referent are not the same as those that are important for storing in a word in long-term memory.
Copyright 2010 Elizabeth Ann Walker