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Lexical–Semantic Organization in Children With Specific Language Impairment Purpose: To determine whether children with specific language impairment (SLI) show deficits in lexical–semantic organization and, if so, whether these deficits are commensurate with their delay in vocabulary size and whether the deficits affect all children with SLI. Method: Fourteen childrenwith SLI, 14 agematches (AM), and 14 expressive vocabulary matches (VM) generated 3 associations to each of 48 words. Associations were coded as semantic (e.g., dog–pet ), clang (e.g., cow–how ), or erroneous (e.g., spoon–Disney ). Results:Relative to the AM children, children with SLI produced fewer semantic responses, more clangs, and more errors. Relative to the VM children, fewer semantic responses and more errors in the children with SLI were found in by-item analyses. Across elicitation trials, semantic responses decreased in the AM and VM children but remained stable in the SLI children. Examination of individual performance in the SLI group revealed that poor semantic performance was associated with a deficit in expressive vocabulary and a gap between receptive and expressive vocabularies. Conclusions: Significant variability in lexical–semantic organization skills exists among children with SLI. Deficits in lexical–semantic organization were demonstrated by a subgroup of children with SLI who likely had concomitant word-finding difficulties. KEY WORDS: lexical–semantic organization, specific language impairment, repeated word association, word-finding difficulties C hildren with specific language impairment (SLI) have documenteddeficits in the semantic domain (Brackenberry & Pye, 2005; Kail &Leonard, 1986). For example, the first sign of SLI is often the late onset of vocabulary acquisition (Bishop, 1997). Also, evidence abounds that childrenwith SLI test lower than age-matched peers on static measures of receptive and expressive vocabulary, indicating a deficit in the breadth of their lexicons (e.g., Gray, Plante, Vance, & Henrichsen, 1999; McGregor, 1997). In the present study we test the hypothesis that children with SLI have deficits in lexical–semantic organization. Lexical–semantic organi- zation is instantiated as the number and accessibility of links froma target word to otherword entries in a semantic network.Weuseda repeatedword association task to derive an estimate of lexical–semantic organization and compared performance between children with SLI and typically de- veloping peers. We also examined within-group variability to investigate the extent to which a deficit in lexical–semantic organization is charac- teristic of the SLI population. Defining Lexical–Semantic Organization Anetworkmetaphor is used to describe lexical–semantic organization. Integral to this network model of semantic activation are the concepts of Li Sheng Karla K. McGregor University of Iowa, Iowa City, and University of Texas–Austin Journal of Speech, Language, and Hearing Research • Vol. 53 • 146–159 • February 2010 • D American Speech-Language-Hearing Association146 on June 11, 2010 jslhr.asha.orgDownloaded from nodes, links, and spreading activation (Collins & Loftus, 1975). In thismodel, words are representedby conceptual nodes. Each node is connected via links to other nodes that share semantic relations. When a node is processed or stimulated, activation spreads out along the network path to other nodes. In a rich semantic network, there are many links connecting the nodes such that the activation of one node primes (or coactivates) many related nodes. For example, the word fingermay readily activate words such as toe, thumb, arm, leg, and shoulder, all of which be- long to the same semantic category as finger. It may also evoke thoughts of another cluster of words such as finger- nail, five, tap, ring, glove, all of which share thematic rela- tions with finger. An important assumption of the semantic network model is that as activation travels outward from the node of origin, it becomes attenuated (Collins & Loftus, 1975). The decrease in activation is inversely related to the ac- cessibility or the strength of the link in the path. In other words, the node that bears the strongest link to the node of origin is the first to be accessed. The acces- sibility of a link depends on how often a person uses or encounters that specific pairing of nodes. For example, finger and toe may be more strongly linked than finger and glove. Frequent exposures to the finger and toe duo and the high degree of overlap in meaning may solidify the link between the two. Building an efficient semantic network involves the formation of many links among word nodes and the forging of strong links between cer- tain nodes. Guided by this semantic network model, we gath- ered data pertinent to two aspects of lexical–semantic organization in children with SLI: the number of links between semantically related nodes and the accessibil- ity of these links. We note that in more current network models (e.g., McClelland, 1995), a one-to-one correspon- dence between words/concepts and nodes is no longer posited. Rather, knowledge is distributed across connec- tions between subsymbolic nodes. The present study is compatible with either theoretical instantiation as both models incorporate the notion of activation spreading across a network that is organized semantically. The Repeated Word Association Task Theword association task is used widely tomeasure semantic knowledge (De Deyne & Storms, 2008). This task has been used in various formats (De Groot, 1989). In a discrete word association task, the participant pro- duces a single response to a word prompt. In a free word association task, the participant produces as many re- sponses as possible to a prompt within a set time limit. In a repeated word association task (Sheng,McGregor, & Marian, 2006), the prompt is repeated multiple times, and each time the participant gives a single response. According to the spreading activation model of se- mantic networks (Collins & Loftus, 1975), upon hearing a prompt (e.g., finger) in aword association task, the con- ceptual node representing that word is activated. Then the activation spreads from one node to others. Nodes bearing strong links to theactivatednode (e.g., toe orhand) are immediately activated and are produced early on in free or repeated word association. Weakly linked nodes (e.g., glove) receive a smaller and/or delayed activation and are produced later in free or repeated word asso- ciation. Further, a word like bookshelf is probably not accessible at all by the activation and never occurs as a response to finger. Through repeated probing, the word association task can yield information about the number and strength of links between semantically relatedwords in a speaker ’s lexicon. Developmental studies reveal increases in semantic responses (e.g., horse–cow, saddle; give–take, gift) in word association tasks during childhood, suggesting that chil- dren are building links between word nodes in their se- mantic networks (e.g., Cronin, 2002; Entwisle, 1966). In addition to semantic responses, young children often gen- erate clangs that bear a pure phonological relationship to the targets. These responses alliterate (e.g., candy–can) or rhyme (e.g., dig–fig) with the targets but do not relate to the targets semantically. Clangs predominate in pre- schoolers and kindergarteners, but this preference is transient and fades out quickly after a year of schooling. Meanwhile, semantic associations show a sharp increase (Cronin, 2002). A shift from phonological to semantic dominance suggests that children abandon a primitive sound-based organization in favor of a more advanced meaning-based organization. However, the heightened at- tention to sound properties during preschool and kinder- garten may be, in part, due to the intensive phonological awareness training that co-occurs with this age period (Justice, 2006). Finally, someassociationsdonotbearperceivable rela- tions to the targets. These casesmay be underscored by an absence of the target word node in the semantic network, an absence of links between related nodes in the network, or perhaps links so tenuous that relevant nodes are in- accessible by the spread of activation. As a result, the re- spondermay succumb to interferences by naming things in the environment, perseverating on a previous response, or producing a random response. During development, the number of both form-based (i.e., clangs) and unrelated re- sponses decreases and the number of semantic responses increases (Cronin, 2002; Entwisle, 1966; Sheng, 2007). Lexical Semantic Development in Children With SLI In laboratory-based training studies, children with SLI demonstrate difficulties learning words. Such Sheng & McGregor: Lexical–Semantic Organization 147 on June 11, 2010 jslhr.asha.orgDownloaded from difficulties are seen in incidental learning contexts in which children are tested on word comprehension and production after a minimal number of exposures to tar- get words (Dollaghan, 1987; Rice, Buhr, &Nemeth, 1990; Rice, Buhr, & Oetting, 1992) and in extended word learn- ing paradigms in which children are taught novel words with didactic input and numerous practice opportunities (Gray, 2003, 2004, 2005; Kiernan & Gray, 1998). In particular, previous studies have indicated poor learning of the semantics of new words in children with SLI. For example, Alt and colleagues (Alt & Plante, 2006; Alt, Plante,&Creusere, 2004) foundpoorer learning of semantic attributes (i.e., color, pattern, eyes, animacy) of novel objects in childrenwithSLI than in age-matched peers. Nash and Donaldson (2005) found inferior learn- ing of the meanings of low-frequency real words (e.g., polka, gauntlet). Munro (2007) used a foreign-language teaching paradigm to examineword learning in children with andwithout SLI. She presented childrenwith novel names (e.g., jum) for known referents (e.g., bird) from a puppy language over a period of 8 weeks. The novel words were presented with pictures and in sentences that aimed to enrich semantic representations (e.g., “This is a jum,” “A jum flies,” “A jum has wings”). To measure semantic learning, Munroe elicited word associations with the newly learned words as stimuli. She found that the typically developing children showed a significantly higher increase in the proportion of semantic associa- tions, which included semantic (e.g., jum–kookaburra, jum–flies) and translation (e.g., jum–bird) responses, from pretraining to posttraining than the children with SLI. In addition, the typically developing children showed a prev- alence of semantic associations over other response types posttraining. In the children with SLI, clangs and un- related associations were both more frequent than se- mantic associations posttraining. Given the SLI children’s weakness in semantic learning, it is logical to predict that these children will have impoverished semantic representations for words stored in their long-termmemory. Impoverished seman- tic representations may, in turn, render these words more difficult to retrieve. Such a link was demonstrated by McGregor and colleagues (McGregor & Apel, 2002; McGregor, Newman, Reilly, & Capone, 2002). In these studies, the children were asked to name, define, and draw pictures for the same target words. Errors in nam- ing were associated with definitions containing few in- formation units and drawings of poor quality, whereas successful naming was seen for words that contained many accurate details in both defining and drawing. If there is a link between word retrieval and rich- ness of semantic representation, one would expect that children who have known deficits in word retrieval to demonstrate poor semantic knowledge. Studies involv- ing children with word-finding difficulties (WFDs) suggest that this is indeed the case. WFDs refer to the inability to find the appropriate word and the use of alternative behaviors (e.g., reformulations; repetitions; use of fillers such as ah or uhm or empty words such as stuff or thing; long pauses; and substitutions) to compen- sate for these difficulties (Messer & Dockrell, 2006). A survey study conducted in theUnited Kingdom suggests that 23%of the general population of language-impaired children also have WFDs (Dockrell, Messer, George, & Wilson, 1998). Clinically,WFDs are often diagnosedwhen a significant discrepancy is detected in a child’s scores on a pair of conormed vocabulary tests that respectively measure word comprehension and production (German, 2000; Gray et al., 1999; Messer & Dockrell, 2006). An important caveat to this diagnostic approach is that a receptive–expressive vocabulary gap, in and of itself, is not an indicator of WFDs because typically develop- ing children also show this pattern. Rather, at the core of this disorder areword retrieval problems that are severe enough to cause concern. Deficits in semantic representations are implicated as a possible locus of WFDs. To illustrate, Dockrell, Messer, George, and Ralli (2003) used a definition task to examine the type of information mapped in the semantic networks of 6- and 7-year-old children with WFDs. They found that children with WFDs were less likely to provide se- mantic category information in definitions of nouns in comparison to age-matched peers. Simmonds, Messer, andDockrell (2005) used a category inclusion task (e.g., “Is this a fruit?”) with children withWFDs (age range = 8;2 [years;months] to 11;3). Compared to age-matched peers, childrenwithWFDs showed significant delays in the speed of recognizing category members, suggesting weakened links between words at various levels of the noun hierarchy. In general, their performance was simi- lar to that of language-matched peers who were 2 years younger. McGregor and Waxman (1998) examined naming errors in children with and without WFDs using a con- trastive naming task. For each target picture (e.g., rose), the experimenters asked questions such as “Is this an animal/a tree/a dandelion?” to elicit labels at various lev- els of the noun hierarchy (e.g., “No, it’s a plant/flower/ rose”). In comparison to age-matched peers, the children with WFDs showed a larger number of indeterminate (e.g., “I don’t know”) and acceptance errors (e.g., “Is this a dandelion?”, “yes!”), indicating that these childrenmay not have stored enough information to discriminate be- tween semantic neighbors. The childrenwithWFDs also showed fewer substitution errors (e.g., tulip for rose) than the controls, indicating that these children were less able to access the correct semantic neighborhood of the target words. Together, these patterns suggest a deficit in the depth of semantic storage in children with WFDs. 148 Journal of Speech, Language, and Hearing Research • Vol. 53 • 146–159 • February 2010 on June 11, 2010 jslhr.asha.orgDownloaded from Recall that childrenwithWFDsare oftenable to com- prehend thewords they fail to produce. The ability to suc- cessfully recognize the word referent among an array of pictures indicates that the children have the word stored to some degree but not in sufficient detail to support word retrieval. Whereas inadequate phonological representa- tion of the word is undoubtedly involved in word retrieval failures (German, 2002), the studies reviewed above sug- gest that a less elaborate semantic representation is also likely to contribute to these difficulties. Individual Variability in Lexical–Semantic Learning Childrenwith SLI are a heterogeneous group (Bishop, 2006). Whereas significant delays in morphosyntactic ability (Rice, 2004) and phonological memory capacity (Dollaghan & Campbell, 1998) have been implicated as clinical markers of SLI, the extent to which a lexical– semantic deficit characterizes the disorder is still un- clear. To this end, Gray (Gray, 2003, 2004, 2005; Kiernan &Gray, 1998) has conducted a series of studies to exam- ine word learning in children with and without SLI. The SLI children in these studies typically have a language impairment of the phonological–syntactic type andwere recruited without a priori criteria on vocabulary scores. Results indicate large variability in word learning out- comes such that some children with SLI perform well within normal limits and some children who do not have a diagnosis of SLI show poor word learning. In Kiernan andGray (1998), 73% of the childrenwith SLI performed within normal limits on the number of words learned. In Gray (2004), 30% of the children with SLI learned as manywords as the typically developing children. In Gray (2003), 23% of the children with SLI demonstrated age- appropriateword learning outcomes. It is still inconclusive what factors account for this great variability. Several learner-internal factors, such as existing vocabulary size, richness of extant semantic storage, ability to fast map, and phonological memory have been implicated as pre- dictors of word learning performance, reflecting the com- plex nature of word learning. The Present Study To date, we know that children with SLI have diffi- culty learning the semantics of words in training studies and that a subgroup of children with SLI—those with WFDs—havedifficulties retrieving semantic information in definition and recall tasks. We have much to learn. What is the status of lexical–semantic organization de- velopment in children from the general SLI popula- tion (i.e., those selected without regard to vocabulary or WFDs)? Do children with SLI have deficits in the num- ber and accessibility of semantic links? If so, what is the degree of these deficits? Do these deficits affect all chil- dren with SLI? These questions are addressed by the present study. We hypothesize that children with SLI have deficits in lexical–semantic organization. We used the repeated word association task to test this hypothesis. We pre- dicted that deficits in lexical–semantic organizationwould bemanifested as fewermature (i.e., semantic) associations and more immature associations (i.e., clangs, errors) in children with SLI than in age-matched peers. In addi- tion to age-matched controls,we included a group of chil- drenwhowerematched to the SLI children on expressive vocabulary. The two comparison groups would help us to determine the degree of semantic deficit relative to age expectations and to general level of vocabulary develop- ment. Significant findings in the latter comparison may indicate the presence of extraordinary difficulties that go beyond a general delay. To examine the accessibility of semantic informa- tion in an individual’s semantic networks, we used the repeated word association task and elicited 3 associa- tions to each of 48 stimuli. Our own research using this paradigm indicated a decrease in semantic responses and a simultaneous increase in unrelated responses acrossmultiple elicitations in typically developing chil- dren whose mean age was 7 or 8 years (Sheng et al., 2006; Sheng, Bedore, & Peña, 2008). Clang responses were at floor in these two studies possibly because the participants had passed the developmental stage when sound-based features are especially salient. Because the existing linkage in the semantic system is sparse in children with SLI, these children will show a smaller number of semantic responses, and this deficit is pre- dicted to surface in the very first trial. With regard to the spread of semantic activation over time, there are two possibilities. First, an impaired system may show the same activation pattern as an intact system, al- though the slopes of the decrease in semantic associa- tionsmay vary. Alternatively, the childrenwith SLImay show a qualitatively different pattern in that semantic associations may stay constant or even increase over trials. In this latter case, an analysis of nonsemantic response types will clarify the sa