The nature of word-finding errors of preschoolers with and without word-finding deficits.

Twelve preschoolers with word-finding deficits (WF) and their age-matched normally developing (ND) peers participated in three tasks requiring word finding: the noun-naming and verb-naming subtests of the Test of Word Finding (TWF-N, TWF-V) and story retelling. The general error profiles of the two subject groups were similar. Semantic errors were always more common than phonological errors and were typically more common than unrelated errors (e.g., "I don't know" responses). The difference in proportions of semantic and phonological substitutions constitutes developmental evidence for lemma and lexeme distinctions as proposed in adult-based models of lexical storage. Furthermore, the predominance of errors that bore semantic relations to their targets produced by both ND and WF groups suggests an early and robust organization of lexical storage into a network of related information. Despite similarities between the two subject groups, the word-finding deficits of the WF group were manifested in two ways. First, compared to the ND group, the WF group demonstrated significantly higher rates of naming errors on all three tasks; second, they demonstrated significantly different proportions of error types on two of the three tasks. Specifically, the WF group produced a lower proportion of related errors on the TWF-V and a lower proportion of semantic errors on the story-retell task. One clinical implication of these findings concerns measurement of treatment outcomes. A reduction in the number of errors as well as a shift in the error profile towards higher proportions of related errors, especially semantic errors, may indicate progress in word-finding development.