Lexical word formation in children with grammatical SLI: a grammar-specific versus an input-processing deficit?

An ongoing controversy is whether an input-processing deficit or a grammar-specific deficit causes specific language impairment (SLI) in children. Previous studies have focussed on SLI childrens' omission of inflectional morphemes or impaired performance on language tasks, but such data can be accounted for by either theory. To distinguish between these theories we study compound formation in a subgroup of SLI children with 'grammatical (G)-SLI'. An input-processing account (e.g. Leonard, L. (1998). Children with specific language impairment. Cambridge, MA: MIT Press), in which perception and production of inflections requires extra processing resources, would predict that G-SLI children will omit the regular plural -s in compounds (e.g. rat-eater). A grammar-specific deficit account (e.g. Ullman, M. & Gopnik, M. (1994) The production of inflectional morphology in hereditary specific language impairment. The McGill Working Papers in Linguistics, 10, 81-118; van der Lely, H. K. J. & Ullman, M. (1996). The computation and representation of past-tense morphology in normally developing and specifically language impaired children. In A. Stringfellow, D. Cahana-Amitay, E. Hughes & A. Zukowski, Proceedings of the 20th Annual Boston University Conference on Language Development (pp. 816-827). Somerville, MA: Cascadilla Press), in which G-SLI children are impaired in regular inflectional morphology, would predict that G-SLI children will produce regular plural -s forms inside compounds (e.g. *rats-eater). We compared the responses of 16 G-SLI subjects (aged 10 years 4 months to 18 years) with those of 36 normally developing control children (24 matched on language ability and 12 matched on age and cognitive ability). All the groups produced irregular plural nouns in compounds (mice-eater). The normally developing children and teenagers rarely, if ever. produced regular plural nouns inside compounds (*rats-eater), whereas the G-SLI subjects did so often. This pattern of results conflicts with the predictions ofthe input-processing deficit account. The findings support the grammar-specific deficit hypothesis. The data rovide further evidence that specialized grammatical abilities may be differentially impaired within the language system.     

In search of meaning: semantic effects on past-tense inflection

Within single-mechanism connectionist models of inflectional morphology, generating the past-tense form of a verb depends upon the interaction of semantic and phonological representations, with semantic information being particularly important for irregular or exception verbs. We assessed this hypothesis in two experiments requiring normal speakers to produce the past tense from a verb stem that takes a regular or exceptional past tense. Experiment 1 revealed significant latency advantages for high- over low-imageability words for both regular verbs (e.g., "lunged" faster than "loved") and exception items (e.g., "drank" faster than "dealt"); but critically, this effect was significantly larger for exceptions than for regulars. Experiment 2 employed a semantic priming paradigm where participants inflected verb stems (e.g., sit) preceded by related (e.g., chair) or unrelated primes (e.g., jug) and revealed a priming effect in accuracy that was confined to the exception items. Our results are consistent with predictions from single-mechanism connectionist models of inflectional morphology and converge with findings from neurological patients and studies of reading aloud.     

Errors of Omission in English-Speaking Children's Production of Plurals and the Past Tense: The Effects of Frequency, Phonology, and Competition

How do English‐speaking children inflect nouns for plurality and verbs for the past tense? We assess theoretical answers to this question by considering errors of omission, which occur when children produce a stem in place of its inflected counterpart (e.g., saying “dress” to refer to 5 dresses). A total of 307 children (aged 3;11–9;9) participated in 3 inflection studies. In Study 1, we show that errors of omission occur until the age of 7 and are more likely with both sibilant regular nouns (e.g., dress) and irregular nouns (e.g., man) than regular nouns (e.g., dog). Sibilant nouns are more likely to be inflected if they are high frequency. In Studies 2 and 3, we show that similar effects apply to the inflection of verbs and that there is an advantage for “regular‐like” irregulars whose inflected form, but not stem form, ends in d/t. The results imply that (a) stems and inflected forms compete for production and (b) children generalize both product‐oriented and source‐oriented schemas when learning about inflectional morphology.     

In search of meaning: Semantic effects on past-tense inflection

Within single-mechanism connectionist models of inflectional morphology, generating the past-tense form of a verb depends upon the interaction of semantic and phonological representations, with semantic information being particularly important for irregular or exception verbs. We assessed this hypothesis in two experiments requiring normal speakers to produce the past tense from a verb stem that takes a regular or exceptional past tense. Experiment 1 revealed significant latency advantages for high- over low-imageability words for both regular verbs (e.g., “lunged” faster than “loved”) and exception items (e.g., “drank” faster than “dealt”); but critically, this effect was significantly larger for exceptions than for regulars. Experiment 2 employed a semantic priming paradigm where participants inflected verb stems (e.g., sit) preceded by related (e.g., chair) or unrelated primes (e.g., jug) and revealed a priming effect in accuracy that was confined to the exception items. Our results are consistent with predictions from single-mechanism connectionist models of inflectional morphology and converge with findings from neurological patients and studies of reading aloud.     

Sex differences in past tense overregularization

Hartshorne and Ullman (2006 ) presented naturalistic language data from 25 children (15 boys, 10 girls) and showed that girls produced more past tense overregularization errors than did boys. In particular, girls were more likely to overregularize irregular verbs whose stems share phonological similarities with regular verbs. It was argued that the result supported the Declarative/Procedural model of language, a neuropsychological analogue of the dual‐route approach to language. In the current study we present experimental data that are inconsistent with these naturalistic data. Eighty children (40 males, 40 females) aged 5;0–6;9 completed a past tense elicitation task, a test of declarative memory, and a test of non‐verbal intelligence. The results revealed no sex differences on any of the measures. Instead, the best predictors of overregularization rates were item‐level features of the test verbs. We discuss the results within the context of dual versus single route debate on past tense acquisition.     

Inflectional morphology in German Williams syndrome

In a recent paper, Clahsen and Almazan (1998) reported a dissociation between unimpaired regular and impaired irregular past tense morphology in English Williams syndrome (WS). Our aim is to investigate whether these findings carry over to another language with different morphological systems. We present data on regular and irregular participles and noun plurals from 2 German WS subjects and 10 controls matching in mental age. For noun plurals, regular morphology is intact in WS, whereas irregular forms are impaired. A similar dissociation is observed for participles: while regular inflection is unimpaired, WS subjects, unlike controls, apply the regular suffix incorrectly to frequent irregular verbs. We discuss our findings against the current debate between connectionist and dualistic approaches to the language faculty.     

Can word formation be understood or understanded by semantics alone?

Arguments concerning the relative role of semantic and grammatical factors in word formation have proven to be a wedge issue in current debates over the nature of linguistic representation and processing. In the present paper, we re-examine claims by Ramscar [Ramscar, M. (2002). The role of meaning in inflection: Why the past tense does not require a rule. Cognitive Psychology, 45, 45-94.] that it is semantic rather than grammatical factors that influence the choice of regular or irregular past tense forms for English verbs. In Experiment 1, we first replicated Ramscar's (2002) experiment, which showed semantic influences on choice of past tense inflection. A novel verb, splink, was introduced in a semantic context that was reminiscent of an existing regular or irregular rhyme verb: blink or drink. Participants favored the past tense form (splinked or splank) that matched that of the semantically similar verb. In Experiment 2, we introduced novel verbs in a context suggesting that they were grammatically derived from nouns (i.e., denominals). Some current symbolic processing models propose that regular past tense forms should be preferred for such forms. When Ramscar's (2002) original contexts for derivational verbs were re-tested in this condition, we replicated his failure to find a preference for regular past tense forms. However, when the contexts were modified to make the grammatical process more salient, we did find a preference for regular past tense forms, suggesting that the derivational status might have been ambiguous in the original materials. In Experiment 3, we tested whether acceptability ratings for regular or irregular past tense forms of grammatically derived verbs could be explained by semantic distance metrics or by ratings of noun-to-verb derivational status. Ratings of semantic distance and grammatical derivation were orthogonal factors in Experiment 3. Only derivational status predicted acceptability ratings for regular past tense forms. Taken together, the present results suggest that semantic factors do not explain the regularization of irregular verbs in derivational contexts, although semantic factors can affect the choice of past tense forms in certain circumstances.     

Imaging the past: Neural activation in frontal and temporal regions during regular and irregular past-tense processing

This article presents fMRI evidence bearing on dual-mechanism versus connectionist theories of inflectional morphology. Ten participants were scanned at 4 Tesla as they covertly generated the past tenses of real and nonce (nonword) verbs presented auditorily. Regular past tenses (e.g., walked, wugged) and irregular past tenses (e.g., took, slept) produced similar patterns of activation in the posterior temporal lobe in both hemispheres. In contrast, there was greater activation in left and right inferior frontal gyrus for regular past tenses than for irregular past tenses. Similar previous results have been taken as evidence for the dual-mechanism theory of the past tense (Pinker & Ullman, 2002). However, additional analyses indicated that irregulars that were phonologically similar to regulars (e.g., slept, fled, sold) produced the same level of activation as did regulars, and significantly more activation than did irregulars that were not phonologically similar to regulars (e.g., took, gave). Thus, activation patterns were predicted by phonological characteristics of the past tense rather than by the rule-governed versus exception distinction that is central to the dual-mechanism framework. The results are consistent with a constraint satisfaction model in which phonological, semantic, and other probabilistic constraints jointly determine the past tense, with different degrees of involvement for different verbs.     

Training generative verb usage by imitation and reinforcement procedures

Three retarded children were trained, using imitation and reinforcement procedures, to produce past and present tense forms of verbs in response to verbal requests. Two types of experimental sessions were arranged: training sessions and probe sessions. During training sessions, a child was trained to produce one verb in both the past and the present tense. Then, in a probe session, the generalization of this training was tested by presenting to the child a series of untrained verbs interspersed with previously trained verbs. Responses to untrained verbs were never reinforced. Training sessions alternated with probe sessions throughout a multiple baseline design involving four classes of verb inflections as the baselines. The results showed that, as past and present tense forms of verbs within an inflectional class were trained, the children correctly produced past and present tense forms of untrained verbs within this class. When verbs from two or more classes were trained, the children correctly produced the verb tenses from each of these classes. Thus, the imitation and reinforcement procedures were effective in teaching generative use of verb inflections.     

Learning without representational change: development of numerical estimation in individuals with Williams syndrome

Experience engenders learning, but not all learning involves representational change. In this paper, we provide a dramatic case study of the distinction between learning and representational change. Specifically, we examined long‐ and short‐term changes in representations of numeric magnitudes by asking individuals with Williams syndrome (WS) and typically developing (TD) children to estimate the position of numbers on a number line. As with TD children, accuracy of WS children's numerical estimates improved with age (Experiment 1) and feedback (Experiment 2). Both long‐ and short‐term changes in estimates of WS individuals, however, followed an atypical developmental trajectory: as TD children gained in age and experience, increases in accuracy were accompanied by a logarithmic‐to‐linear shift in estimates of numerical magnitudes, whereas in WS individuals, accuracy increased but logarithmic estimation patterns persisted well into adulthood and after extensive training. These findings suggest that development of numerical estimation in WS is both arrested and atypical.     

An Elicited‐Production Study of Inflectional Verb Morphology in Child Finnish

Many generativist accounts (e.g., Wexler, 1998) argue for very early knowledge of inflection on the basis of very low rates of person/number marking errors in young children's speech. However, studies of Spanish (Aguado‐Orea & Pine, 2015) and Brazilian Portuguese (Rubino & Pine, 1998) have revealed that these low overall error rates actually hide important differences across the verb paradigm. The present study investigated children's production of person/number marked verbs by eliciting present tense verb forms from 82 native Finnish‐speaking children aged 2;2–4;8 years. Four main findings were observed: (a) Rates of person/number marking errors were higher in low‐frequency person/number contexts, even excluding children who showed no evidence of having learned the relevant morpheme, (b) most errors involved the use of higher frequency forms in lower frequency person/number contexts, (c) error rates were predicted not only by the frequency of person/number contexts (e.g., 3sg > 2pl) but also by the frequency of individual “ready‐inflected” lexical target forms, and (d) for low‐frequency verbs, lower error rates were observed for verbs with high phonological neighborhood density. It is concluded that any successful account of the development of verb inflection will need to incorporate both (a) rote‐storage and retrieval of individual inflected forms and (b) phonological analogy across them.     

Dual-route processing of complex words: New fMRI evidence from derivational suffixation

Many behavioral models of the comprehension of suffixed words assume a dual-route mechanism in which these words are accessed sometimes from the mental lexicon as whole units and sometimes in terms of their component morphemes (such as happi+=ness). In related neuropsychological work, Ullman et al. (1997) proposed a dual-route model for past tense processing, in which the lexicon (used for access to irregularly inflected forms) corresponds to declarative memory and a medial temporal/ parietal circuit, and the rule system (used for computation of regularly inflected forms) corresponds to procedural memory and a frontal (including Broca’s area)/basal ganglia circuit. We used functional MRI and a memory encoding task to test this model for derivationally suffixed words, comparing those words that show evidence of decompositional processing in behavioral studies (-ness, -less, and -able words) with derived words that do not show decomposition effects (-ity and -ation words). By examining Broca’s area and the basal ganglia as regions of interest, we found that “decomposable” derived and inflected words showed increases in activity relative to nondecomposable suffixed words. Results support a dual-route model of lexical access of complex words that is consistent with the Ullman et al. proposal.     

The role of type and token frequency in using past tense morphemes correctly

Type and token frequency have been thought to be important in the acquisition of past tense morphology, particularly in differentiating regular and irregular forms. In this study we tested the role of frequency in two ways: (1) in bilingual children, who typically use and hear either language less often than monolingual children and (2) cross-linguistically: French and English have different patterns of frequency of regular/irregular verbs. Ten French-English bilingual children, 10 French monolingual and 10 English monolingual children between 4 and 6 years watched a cartoon and re-told the story. The results demonstrated that the bilingual children were less accurate than the monolingual children. Their accuracy in both French and English regular and irregular verbs corresponded to frequency in the input language. These results are consistent with the hypothesis that children learn past tense morphemes by analogy with other words in their vocabularies. We propose a developmental sequence based on conservative generalization across a growing set of verbs.     

Small Subitizing Range in People with Williams syndrome

Recent evidence suggests that the rapid apprehension of small numbers of objects-- often called subitizing-- engages a system which allows representation of up to 4 objects but is distinct from other aspects of numerical processing. We examined subitizing by studying people with Williams syndrome (WS), a genetic deficit characterized by severe visuospatial impairments, and normally developing children (4-6.5 years old). In Experiment 1, participants first explicitly counted displays of 1 to 8 squares that appeared for 5 s and reported "how many". They then reported "how many" for the same displays shown for 250 ms, a duration too brief to allow explicit counting, but sufficient for subitizing. All groups were highly accurate up to 8 objects when they explicitly counted. With the brief duration, people with WS showed almost perfect accuracy up to a limit of 3 objects, comparable to 4 year-olds but fewer than either 5 or 6.5 year-old children. In Experiment 2, participants were asked to report "how many" for displays that were presented for an unlimited duration, as rapidly as they could while remaining accurate. Individuals with WS responded as rapidly as 6.5 year-olds, and more rapidly than 4 year-olds. However, their accuracy was as in Experiment 1, comparable to 4 year-olds, and lower than older children. These results are consistent with previous results indicating that people with WS can simultaneously represent multiple objects, but that they have a smaller capacity than older children, on par with 4 year-olds. This pattern is discussed in the context of normal and abnormal development of visuospatial skills, in particular those linked to the representation of numerosity.     

Small subitizing range in people with Williams syndrome

Recent evidence suggests that the rapid apprehension of small numbers of objects—often called subitizing—engages a system which allows representation of up to 4 objects but is distinct from other aspects of numerical processing. We examined subitizing by studying people with Williams syndrome (WS), a genetic deficit characterized by severe visuospatial impairments, and normally developing children (4–6.5 years old). In Experiment 1, participants first explicitly counted displays of 1 to 8 squares that appeared for 5 s and reported “how many”. They then reported “how many” for the same displays shown for 250 ms, a duration too brief to allow explicit counting, but sufficient for subitizing. All groups were highly accurate up to 8 objects when they explicitly counted. With the brief duration, people with WS showed almost perfect accuracy up to a limit of 3 objects, comparable to 4-year-olds but fewer than either 5- or 6.5-year-old children. In Experiment 2, participants were asked to report “how many” for displays that were presented for an unlimited duration, as rapidly as possible while remaining accurate. Individuals with WS responded as rapidly as 6.5-year-olds, and more rapidly than 4-year-olds. However, their accuracy was as in Experiment 1, comparable to 4-year-olds and lower than older children. These results are consistent with previous findings, indicating that people with WS can simultaneously represent multiple objects, but that they have a smaller capacity than older children, on par with 4-year-olds. This pattern is discussed in the context of normal and abnormal development of visuospatial skills, in particular those linked to the representation of numerosity.     

The competition–compensation account of developmental language disorder

Children with developmental language disorder (DLD) regularly use the bare form of verbs (e.g., dance) instead of inflected forms (e.g., danced). We propose an account of this behavior in which processing difficulties of children with DLD disproportionally affect processing novel inflected verbs in their input. Limited experience with inflection in novel contexts leads the inflection to face stronger competition from alternatives. Competition is resolved through a compensatory behavior that involves producing a more accessible alternative: in English, the bare form. We formalize this hypothesis within a probabilistic model that trades off context-dependent versus independent processing. Results show an over-reliance on preceding stem contexts when retrieving the inflection in a model that has difficulty with processing novel inflected forms. We further show that following the introduction of a bias to store and retrieve forms with preceding contexts, generalization in the typically developing (TD) models remains more or less stable, while the same bias in the DLD models exaggerates difficulties with generalization. Together, the results suggest that inconsistent use of inflectional morphemes by children with DLD could stem from inferences they make on the basis of data containing fewer novel inflected forms. Our account extends these findings to suggest that problems with detecting a form in novel contexts combined with a bias to rely on familiar contexts when retrieving a form could explain sequential planning difficulties in children with DLD.

Research Highlights

• Generalization difficulties with inflectional morphemes in children with Developmental Language Disorder arise from these children's limited experience with novel inflected forms.
• Limited experience with a form in novel contexts could lead to a storage bias where retrieving a form often requires relying on familiar preceding stems.
• While generalization in typically developing models remains stable across a range of model parameters, certain parameter values in the impaired models exaggerate difficulties with generalization.
• Children with DLD compensate for these retrieval difficulties through accessibility-driven language production: they produce the most accessible form among the alternatives.

     

Spatial breakdown in spatial construction: evidence from eye fixations in children with Williams syndrome

We investigated the role of executive and spatial representational processes in impaired performance of block construction tasks by children with Williams syndrome (WS), a rare genetic defect that results in severely impaired spatial cognition. In Experiment 1, we examined performance in two kinds of block construction tasks, Simple Puzzles, in which block faces contained a single color, and Complex, in which some block faces contained an arrangement of two colors. WS and control children were comparable in their ability to solve simple puzzles, and showed similar eye-fixation patterns, suggesting that basic executive processes were intact. However, WS children were severely impaired in their ability to solve complex puzzles. In these puzzles, WS children fixated the complex puzzle models and checked their partial solutions less often than normal children, but they were comparable in their ability to detect errors in their copies and almost exclusively made repairs to copies that were, in fact, incorrect. We conjecture that the abnormal fixation patterns were a consequence of impoverished spatial representations, rather than a cause of it. This conjecture was tested in Experiment 2, where we examined children's capacity to match and place individual blocks without engaging the complex executive processes required to carry out a complete puzzle solution. We found serious deficiency among WS children in both aspects of spatial representation. Moreover, estimates of the errors in representing the identity and location of model blocks derived from Experiment 2 provided a good account of the observed errors in the block construction task of Experiment 1.     

Children's early productivity with verbal morphology

Three studies using the intermodal preferential looking paradigm examined onset of productive comprehension of tense/aspect morphology in English. When can toddlers understand these forms with novel verbs and novel events? The first study used familiar verbs and showed that 26–36-month olds correctly matched a past/perfective form (-ed or irregular past) to a completed version of an event and a present/imperfective (is V-ing) to the ongoing version of the same event. The second study used novel verbs and events and found that 33-month olds failed to use tense/aspect morphology to choose between completed and ongoing versions of the same event. The third study also used novel verbs and events but simplified the processing demands of the task in several ways (using initial priming of the events and classes of meaning, using different events within test pairs). This study found that 30-month olds successfully used tense/aspect morphology to choose between ongoing and completed novel events. The results demonstrate that children have productive command of tense/aspect morphology by 30 months and have therefore begun the process of creating an abstract grammar containing this element.     

Object recognition with severe spatial deficits in Williams syndrome: sparing and breakdown

Williams syndrome (WS) is a rare genetic disorder that results in severe visual-spatial cognitive deficits coupled with relative sparing in language, face recognition, and certain aspects of motion processing. Here, we look for evidence for sparing or impairment in another cognitive system-object recognition. Children with WS, normal mental-age (MA) and chronological age-matched (CA) children, and normal adults viewed pictures of a large range of objects briefly presented under various conditions of degradation, including canonical and unusual orientations, and clear or blurred contours. Objects were shown as either full-color views (Experiment 1) or line drawings (Experiment 2). Across both experiments, WS and MA children performed similarly in all conditions while CA children performed better than both WS group and MA groups with unusual views. This advantage, however, was eliminated when images were also blurred. The error types and relative difficulty of different objects were similar across all participant groups. The results indicate selective sparing of basic mechanisms of object recognition in WS, together with developmental delay or arrest in recognition of objects from unusual viewpoints. These findings are consistent with the growing literature on brain abnormalities in WS which points to selective impairment in the parietal areas of the brain. As a whole, the results lend further support to the growing literature on the functional separability of object recognition mechanisms from other spatial functions, and raise intriguing questions about the link between genetic deficits and cognition.