Measuring lexical diversity in children who stutter: application of vocd

There is growing but equivocal evidence that the language abilities of young children who stutter (CWS) may be depressed when compared to those of their fluent peers. In particular, the lexical skills of CWS have variously been reported to be weaker or stronger than comparison children in a number of recent studies. One source for such disagreement may be the measures used to compute lexical characteristics of these children’s spoken conversations. In this study, we examined the concurrent validity of two measures of lexical diversity in spontaneous language samples, Type-Token Ratio (TTR) and the newly developed utility vocd (Malvern & Richards, 1997), using a standard test of expressive vocabulary as the comparison measure. Findings indicated that vocd values (“D”) correlated well with standardized measures of expressive vocabulary, while TTR values did not. In addition, both the standardized measure and vocd revealed significantly poorer expressive lexical skills of CWS, whereas TTR analyses did not evidence this difference. Results are discussed in relation to the relative strength of vocd over TTR as a method for describing lexical characteristics of the spontaneous language samples of this population.

Educational objectives: The reader will learn about and be able to (1) identify several common measures of conversational vocabulary and the strengths and weaknesses of each, and (2) compare the performance of the young CWS in this study to their normally fluent peers in terms of vocabulary performance on both formal and conversational measures of vocabulary.