تناوب استفاده فعل در کودکان خردسال که لکنت زبان دارند
|کد مقاله||سال انتشار||مقاله انگلیسی||ترجمه فارسی||تعداد کلمات|
|33502||2007||16 صفحه PDF||سفارش دهید||8055 کلمه|
Publisher : Elsevier - Science Direct (الزویر - ساینس دایرکت)
Journal : Journal of Fluency Disorders, Volume 32, Issue 2, 2007, Pages 79–94
Several recent studies have suggested that young children who stutter (CWS) tend to show depressed lexical performance relative to peers. Given the developmental literature as well as several studies of verb processing in individuals who stutter, verbs may pose a particular challenge for this group. The purpose of the present study was to examine verb use in CWS. In theory, if young CWS differ in their production of verbs, this finding would partially explain the findings of studies that probed conversational vocabulary skills more generally. Fifteen CWS and 15 children who do not stutter (CWNS) participated in a play-based conversational sample with a parent. Samples were analyzed for the total number of verbs, the number of different verbs, and the proportion of general all-purpose (GAP) verbs within the samples. CWS produced significantly fewer different verbs and total verbs than the CWNS. However, previously reported near-significant differences in utterance length between groups would appear to temper the robustness of this finding. The groups did not differ in the proportion of GAP verbs used, suggesting that the CWS did not over-rely on GAP verbs in conversational language production but rather used these verbs to the same extent as their peers.
There is a longstanding literature that has examined whether the language abilities of children who stutter (CWS) are equivalent to those of children who do not stutter (CWNS; e.g., see Bernstein Ratner, 1997, for a review). The need to more closely examine lexical features of language produced by CWS is motivated by several recent findings suggesting depressed lexical performance of CWS relative to peers (Anderson & Conture, 2000; Bernstein Ratner & Silverman, 2000; Pellowski & Conture, 2005; Silverman & Bernstein Ratner, 2002; see Hall, 2004, for a discussion). For example, Bernstein Ratner and Silverman (2000) assessed 15 CWS, each of whom was within 4 months post-onset of stuttering, and 15 normally fluent peers. A variety of language skills, including lexical skills, were examined through formal testing and language sample analysis. The results indicated that the CWS did not differ significantly from peers in their one-word receptive vocabulary scores, but they had significantly lower expressive vocabulary scores than the CWNS. Later inspection of the children's conversational vocabulary, using vocd ( Malvern & Richards, 1997; Malvern, Richards, Chipere, & Duran, 2004), a measure of lexical diversity that takes into account differences in sample size across participants, revealed that the samples of CWS yielded significantly lower vocd values than those of CWNS ( Silverman & Bernstein Ratner, 2002). More recently, Pellowski and Conture (2005) administered a lexical priming task to children, aged 3;0–5;11 years. They found that, though CWNS benefited from a semantically related prime, demonstrating faster speech reaction times when a prime was presented, CWS did not display the same advantage under the prime condition. The authors interpreted these findings as suggestive of lexical encoding difficulties for CWS. Young children who have recently begun to stutter are a particularly relevant population with respect to questions of the relationship between language and stuttering, because these children are in the early stages of their language development; the interaction between language learning and stuttering is most likely to be seen during this crucial time in development. Although there is a sizable and growing body of studies examining vocabulary performance of CWS on standardized measures (e.g., Anderson & Conture, 2000; Anderson, Pellowski, & Conture, 2005; Bernstein Ratner & Silverman, 2000; Murray & Reed, 1977; Ryan, 1992, Ryan, 2001 and Westby, 1974) and conversational language samples (e.g., Silverman & Bernstein Ratner, 2002; Watkins & Yairi, 1997; Watkins, Yairi, & Ambrose, 1999; Westby, 1974), to our knowledge, none have explored the underlying qualities of the words that comprise the lexicon of CWS. 1.1. Acquisition and use of verbs Verbs, or action words, are a particularly interesting class for exploration of observed lexical differences. The developmental literature suggests that verbs are more difficult than nouns for young children developing language (e.g., Camarata & Leonard, 1986; Gentner, 1978 and Gentner, 1982; Gleitman, Cassidy, Nappa, Papafragou, & Trueswell, 2005; Lidz & Gleitman, 2004). For example, Camarata and Leonard (1986) examined young, typically developing children between the ages of 1;8 and 2;1 years in the production of emerging consonants within each child's phonological repertoire. For each child, 10 nonword objects and 10 nonword actions were designed such that their phonological makeup consisted of emerging sounds within the child's repertoire. Object and action nonwords were matched for consonant and syllable structure. Following eight sessions involving exposure to the nonwords, children responded to post-test production probes of the target object or action. Results were that children produced emerging consonants less accurately in novel action words than in novel object words. The authors suggested that the results point to an interaction between phonology and semantics. Thus, the greater semantic complexity of action words manifests itself in a greater number of phonological errors on action words compared to object words. First verbs tend to emerge later than first nouns in children's language development. One explanation for this observation is that, while nouns can be learned individually, following exposure to the concepts to which they are linked, verbs are learned based on an understanding of relationships between objects or ideas (e.g., see Gentner, 1978 and Gentner, 1982, for discussions). Thus, verb learning is critical from a developmental standpoint, because it plays a pivotal role in the conceptualization of the syntactic structure of utterances (Gentner, 1978, Gentner, 1982, Gleitman et al., 2005 and Gropen, 2000; Lidz & Gleitman, 2004). Verbs can be categorized into groups of similar meaning, such as verbs of giving, showing, creating, moving, etc. Verbs within categories tend to have the same argument structure, which can help a child infer syntactic information about a new verb, based on similar verbs the child already knows (see Gropen, 2000, for a detailed discussion). 1.2. GAP verb use An aspect of verb use, one that has been an area of focus within the specific language impairment (SLI) literature (Kelly, 1997; Rice & Bode, 1993; Thordardottir & Ellis Weismer, 2001; Watkins, Rice, & Moltz, 1993), is the extent to which children rely on general all-purpose (GAP) verbs, high-frequency verbs that can take the place of more specific lexical items. For example, a child might choose go, a GAP verb that can take the place of a large set of more specific verbs, including leave, ride, walk, drive, sail, etc. GAP verbs are generally acquired early in development. Campbell and Tomasello (2001) have argued that children's development and use of GAP verbs (or “light” verbs) early on is most likely due to the frequency with which input to children contains these verbs. That is, one interpretation is that children use these verbs early because adults use them with much greater frequency and across a much greater range of contexts than more specific (or “heavy”) verb choices. Another explanation, which is not mutually exclusive, is that children (as well as adults) rely to a greater extent on GAP verbs because it is more efficient to retrieve these verbs from the mental lexicon than a more specific verb. Whether or not either of these possibilities is correct, it is clear that children with typically developing language do, in fact, frequently use GAP verbs in their output (e.g., see Goldberg, 1999, for a discussion). From a methodological perspective, studies of conversational verb use in CWS should consider the potential impact of GAP verbs on subsequent lexical diversity measurement. Given that GAP verbs are high frequency lexical items (suggesting quick lexical retrieval) and are motorically simple, monosyllabic words, one hypothesis is that CWS may rely on GAP verbs to a greater extent than normally fluent peers. That is, for CWS, the use of GAP verbs may not only serve as a linguistic strategy (i.e., making lexical retrieval more efficient), as it appears to for CWNS, but also serve as a motoric strategy for fluent speech production. Thus, if CWS use GAP verbs to a greater extent than CWNS, this finding would uncover at least one factor contributing to findings of reduced lexical diversity in CWS. Studies of GAP verb use in children with SLI have sought to assess whether children with SLI differ from peers in their use of these verbs as a potential language production strategy (Kelly, 1997; Rice & Bode, 1993; Thordardottir & Ellis Weismer, 2001; Watkins et al., 1993). These studies provide a methodological base for the present study, in that each resulted in a list of GAP verbs emerging from the samples. Although the methods by which the authors arrived at their lists varied somewhat, the word lists themselves are fairly similar. 1.3. Verb use in individuals who stutter The extent of GAP verb use in CWS, as well as the range of verbs used by these children relative to normally fluent peers, is an important issue in several respects. First, as has been suggested within the developmental literature, the use of GAP verbs may serve to make language production more efficient, because these verbs are high frequency and motorically simple. It is possible, then, that CWS, in an attempt to remain fluent, may choose a motorically simple word choice over a more specific lexical item with greater phonological complexity. There has been some suggestion in the treatment literature that CWS may differ in the inferences they make about how to “change” their speech in order to produce fluent speech. Onslow, Bernstein Ratner, and Packman (2001), for example, found that two CWS who received treatment with response contingent stimulation (defined as “time-out”) reduced the frequency of their stuttering; however, for one child, the reduction was accompanied by vowel duration changes in speech, and for the other child, the reduction was accompanied by a change in lexical diversity and language productivity (also see Bonelli, Dixon, Bernstein Ratner, & Onslow, 2000; Onslow, Packman, Stocker, van Doorn, & Siegel, 1997). Although the present study is not a treatment study, findings of Onslow et al. (2001) and Bonelli et al. (2000) suggest that CWS, when not provided specific fluency strategies by a clinician, may infer the speech and language changes needed to produce fluent speech. A second issue that highlights the importance of understanding verb use in CWS is that, if CWS are, in fact, using a greater proportion of GAP verbs than peers or a smaller range of different verbs overall, then previous findings of differences in vocabulary diversity overall may be impacted by the children's verb use, in particular. That is, the use of GAP verbs can have the effect of making a child's expressive vocabulary appear worse than it is. If CWS produce a higher proportion of GAP verbs than peers, traditional measures of lexical diversity, such as type-token ratio (Templin, 1957), number of different words (Templin, 1957; Watkins, Kelly, Harbers, & Hollis, 1995), and vocd ( Malvern & Richards, 1997) would yield results suggesting poorer lexical skills. The same is true of verb use in general; if it were found that CWS use fewer verbs than CWNS, reduced verb use could be the underlying factor (or one of several factors) that results in the group differences observed in lexical diversity overall. It appears that verb use has not been an area of focus in CWS, but several studies have employed tasks involving verb generation or syntactic processing in adults who stutter (AWS; Bosshardt & Fransen, 1996; Cuadrado & Weber-Fox, 2003; De Nil, Kroll, & Houle, 2001; Prins, Main, & Wampler, 1997). For example, Prins et al. examined naming latency in AWS and normally fluent counterparts. They found that the AWS had significantly longer naming latencies than adults who do not stutter (AWNS), a difference which was six times longer for verb stimuli than for noun stimuli. More recently, Cuadrado and Weber-Fox (2003) administered a grammaticality judgment task to AWS and AWNS. The grammaticality judgments involved making yes/no decisions about verb agreement. Online and offline versions of the task were administered, and ERPs were measured during the online task. The investigators found that the AWS were significantly less accurate than AWNS in the online grammaticality judgment task, but there was no significant difference on the offline, paper-and-pencil task. In addition, ERP findings suggested that, while the ERPs of AWNS showed the predicted P600 pattern observed in previous investigations, the AWS showed an atypical P600 pattern, reduced in amplitude and limited to two anterior lateral sites of the right hemisphere. Thus, results suggest subtle difficulties in grammatical (verb agreement) processing in AWS relative to AWNS. In sum, then, given findings that (a) the acquisition of verbs represents a challenging linguistic milestone for typically developing children (e.g., Gentner, 1978 and Gentner, 1982), and (b) AWS appear to show some subtle differences in verb processing (Cuadrado & Weber-Fox, 2003; De Nil et al., 2001 and Prins et al., 1997), examination of lexical diversity of verbs in CWS would appear to be an important next step. Moreover, given that GAP verbs are high frequency and motorically simple, supplying a potential motivation for their use by CWS in attempting to maintain fluent speech, examination of GAP verb use in CWS seems particularly important in understanding verb use in these children. Particularly in light of observed differences in lexical diversity overall (e.g., Silverman & Bernstein Ratner, 2002), it seems critical to explore verb use as a possible underlying variable impacting the measurement of lexical diversity. The purposes of this study are to examine verb use in the spontaneous language of CWS and to test the hypothesis that CWS use GAP verbs to a greater extent than CWNS in their language output. The research questions were: (a) Do CWS differ from CWNS in the number of different verbs (NDV) and/or the total number of verbs (TNV) produced in their language samples? and (b) Do CWS differ from normally fluent peers in the proportion of verbs that are GAP verbs, both as defined by previous studies of GAP verb use, and as defined by verbs that occurred within the present samples with high frequency?