Judgments of Omitted BE and DO in Questions as Extended Finiteness Clinical Markers of Specific Language Impairment (SLI) to 15 Years

Purpose—Clinical grammar markers are needed for children with SLI older than 8 years. This study followed children studied earlier on sentences with omitted finiteness to determine if affected children continue to perform at low levels and to examine possible predictors of low performance. This is the first longitudinal report of grammaticality judgments of questions. Method—Three groups of children participated: 20 SLI, 20 age controls and 18 language-matched controls, followed from ages 6–15 years. An experimental grammaticality judgment task was administered with BE copula/auxiliary and DO auxiliary in Whand Yes/No questions for 9 times of measurement. Predictors were indices of vocabulary, nonverbal intelligence, and maternal education. Results—Growth curve analyses show that the affected group performed below the younger controls at each time of measurement, for each variable. Growth analyses show linear and quadratic effects for both groups across variables, with the exception of BE acquisition which was flat for both groups. The control children reached ceiling levels; the affected children reached a lower asymptote. Conclusions—The results suggest an on-going maturational lag in finiteness marking for affected children with promise as a clinical marker for language impairment in school-aged and adolescent children and probably adults as well. Investigations of potential clinical markers for the condition of SLI yielded significant advances in the last ten to fifteen years as the field moved toward genetic investigations in need of behavioral phenotypes (cf. Tager-Flusberg and Cooper, 1999) and longitudinal growth studies in need of conceptually linked measures over a wide age span (Law, Tomblin and Zhang, 2008; Rice, 2007; in press). The study of finiteness marking (sometimes referred to as “grammatical tense marking”) was noted by Tager-Flusberg and Cooper (1999) as a promising clinical marker. This line of investigation includes the earliest study of finiteness marking by Rice, Wexler and Cleave (1995) and the first longitudinal study of the growth of finiteness marking by Rice, Wexler and Hershberger (1998). Evidence for finiteness as a clinical marker has been widely replicated, as reviewed below. Bishop, Adams and Norbury (2005) reported strong heritability for a finiteness marker independent of non-word repetition heritability in their study of 6-year-old twins. Falcaro et al. (2008) report significant familial aggregation and gene linkage for tense marking for affected individuals. NIH Public Access Author Manuscript J Speech Lang Hear Res. Author manuscript; available in PMC 2010 December 1. Published in final edited form as: J Speech Lang Hear Res. 2009 December ; 52(6): 1417–1433. doi:10.1044/1092-4388(2009/08-0171). N IH PA Athor M anscript N IH PA Athor M anscript N IH PA Athor M anscript Although progress is evident, there are notable gaps in the available information about finiteness marking. The first gap to be noted is that the evidence is age-constrained. The evidence is strongest for the early childhood period, roughly 3 to 8 years of age (cf. Rice and Wexler, 2001), but at the upper age levels for this period on the available grammatical structures and tasks the difference between affected and control groups narrows. The issue is that the tasks that work well for the younger children in this age range are a bit too easy for the upper range, even for affected children. Clinical finiteness markers for children at the next levels of development are needed. Second, the relationship between early finiteness marking abilities/weaknesses and later extensions of this domain into other linguistic contexts is not fully worked out. There is a need for theoretically motivated extensions of the linguistic contexts known to be problematic for young children with SLI to linguistic contexts that are conceptually linked to early weaknesses in finiteness and are age-appropriate for older children. Such a marker would be useful for research as well as clinical applications. For example, we need markers for the identification of affected children not previously identified in clinical situations and also in family/genetic studies of siblings of affected children. A third gap is closely related to the other two. The set of grammatical morphemes that express finiteness marking poses many challenges for language acquisition, such as the need to learn multiple forms, the grammatical properties of finiteness and the underlying syntactic structures. Current investigations examine contrasting accounts of the early stages of finiteness acquisition. One matter of dispute is the extent to which the acquisition process is guided by common functions across the set of morphemes (cf Guasti, 2002), with error patterns predicted by the common function, versus a more isolated acquisition process of individual forms driven by the differentiating properties of individual morphemes within the set (such as phonological form or frequency of use in adult utterances) (cf Pine, Conti-Ramsden, Joseph, Lieven and Serratrice, 2008). Long-term longitudinal data can help clarify the extent to which the shared feature of finiteness underlies growth, or if growth varies across forms, and the extent to which persisting weaknesses in finiteness marking is evident across forms. This information will be helpful in evaluating competing accounts of the ways in which children acquire the finiteness marking properties of the adult grammar. A fourth gap is the lack of direct longitudinal assessments of the finiteness marker in older children to determine if the children “out-grow” this deficit or if it persists over time. We need to know if the growth in finiteness marking during the early childhood period indicates that the grammatical immaturity in finiteness marking has been resolved, or if there is likely to be ongoing weakness evident in later-acquired linguistic contexts. Although there is growing evidence to suggest that the language impairments of children with SLI are likely to remain into adulthood (cf. Johnson et al, 1999) the evidence base largely consists of performance on omnibus measures (Johnson et al, 1999; Law, Tomblin and Zhang, 2008) or cross-sectional studies of affected and control children on a variety of experimental measures of language or processing tasks (cf. Montgomery and Windsor, 2007). In particular, there is a need for longitudinal assessments of children whose earlier levels of performance on related tasks are known, as a first step in the development of clinical grammar markers suitable for growth studies across a wide age range. This need is evident in studies of genetic etiology. Falcaro et al (2008) examined a behavioral phenotype of past tense marking on lexical verbs in a participant sample with a mean age of 14 years. They found significant familial aggregation when tense marking was treated as a binary/categorical variable, but not when treated as a continuous variable. Linkage for the binary measure was observed on chromosome 19; for the continuous measure, linkage was significant on chromosome 16 as well as 19, although stronger on 19. They suggest “that tense Rice et al. Page 2 J Speech Lang Hear Res. Author manuscript; available in PMC 2010 December 1. N IH PA Athor M anscript N IH PA Athor M anscript N IH PA Athor M anscript marking may not be a phenotypic trait that is measurable as a continuous dimension across development but instead may be a skill in which competence is either acquired or not acquired by early school age, comparable to a Piagetian stage in learning. In this sense, qualitative distinctions in the trait is what appears to be familial...” (p. 399). Quantitative variation is attributable, under this account, to non-familial factors, such as age-related differences in motivation or attention to task. The relevance here is that a grammar marker related to earlier finiteness marking that shows variation in older children would be very valuable as a potential phenotype to help clarify genetically influenced variation and evaluate the interpretation of Falcaro, et al (2008). This study aims to fill these four gaps in the literature by following up on the children who were first studied longitudinally for the finiteness marker from ages 3 to 8;8 years (Rice, Wexler and Hershberger, 1998) and later on a judgment task of declarative sentences with omitted finiteness (Rice, Wexler and Redmond, 1999). In this study a grammaticality judgment task is designed to track finiteness marking in single-clause questions as a theoretically motivated extension of the earlier investigation of simple declaratives. This involves more detailed information about the acquisition of copula and auxiliary BE and auxiliary DO in whand yes/ no questions. The study tracks the affected children from 8 to 15 years of age, with the prediction that affected children should be more likely than control groups to accept omitted BE and DO forms in questions, for a period of time that extends beyond what is evident in simple declarative clauses. Shared properties of finiteness marking in matrix clauses and questions for auxiliary and copula BE and auxiliary DO in questions The property of finiteness marking is widely accepted as a central grammatical property that links matrix clauses and questions (see Quirk, Greenbaum, Leech and Swartvik, 1985). X’ theory provides a precise model of the relationship between finiteness marking in matrix clauses and questions (cf Chomsky, 1993,1995; Haegeman1994), a model that arguably captures universal properties of grammar. Within this model, morphology is tightly related to syntax because morphological elements carry word order and phrasal movement requirements, hence the term “morphosyntax” (Pollack, 1989). In this model of the adult grammar, simple matrix clauses consist of a Noun Phrase (NP) and a Verb Phrase (VP). Verbs carry Tense (TNS) and Agreement (AGR) features that are essential for clause structure. An additional projection, the Inflection Phrase (IP), is needed for finiteness marking to meet the requirements of TNS and AGR checking in simple clauses. See Figure 1. The subject NP is assumed to originate in the “specifier” position to the left of V and move to the “specifier” position to the left of the finite verb in I position. The finite verb originates in the V (“head”) of the VP and, if it is an auxiliary like is, moves to the I (head) of the IP. Note that this model lays out the clausal architecture that describes a site for finiteness marking as well as distributional requirements for the placement of related grammatical elements, such as negation (cf Pollock, 1989). The model requires a single occupant of the finiteness site per clause, thus capturing the ungrammaticality of sentences like *the bug is sleeps in the bed and the fact that progressive –ing, although a verbal affix, does not mark finiteness because it appears in combination with is as the occupant of the finiteness slot in the clause (*he running is ungrammatical). Copula BE, as in The bug is happy, occupies the same site in the clause, with the predicate adjective in the lower VP. Such distributional patterns and other linguistic characteristics identify the following set of morphemes, among others, as finiteness markers in English: Third person singular non-past –s on thematic/lexical verbs, regular and irregular past tense on thematic/lexical verbs, copula and auxiliary BE and auxiliary DO. DO has special properties. In matrix declarative clauses auxiliary DO does not appear in affirmative clauses unless it has an additional meaning of emphasis, such as “He does want to go!” In Rice et al. Page 3 J Speech Lang Hear Res. Author manuscript; available in PMC 2010 December 1. N IH PA Athor M anscript N IH PA Athor M anscript N IH PA Athor M anscript negative clauses DO must be inserted to precede the negation marker not before lexical verbs, as in “She does not go home.” Under this model, questions are derived from the matrix clauses via movement of TNS and AGR features to a projection above (i.e. to the left of) the IP, known as the Complementizer Projection (CP). This projection also includes two sites, C and the specifier of C’ position. Questions can be formed as yes/no questions in which the copula or auxiliary occupy the C position, such as “Is the bug happy?” See Figure 2. Questions can also be formed using a wh form (including who, what, when, where, why as well as how, among others), which occupies the specifier of C’position to the left of C which is occupied by the auxiliary or copula. BE auxiliaries move out of the I position into C whereas progressive forms of the thematic/lexical verb are left in the lower VP; BE copulas move out of the I position into C with the predicate adjectival phrase left in the lower VP. As shown in Figure 3, the wh-element at the beginning of the question represents a thematic element that originates in the lower VP. Non-emphatic auxiliary DO also occupies the C position in CP. It is not clear if DO is generated directly in this position or if it moves from IP in the same way as BE (see Chomsky, 1995, p. 164, footnote 20). The special properties of DO auxiliary in questions is related to the fact that English, unlike other languages, does not allow the thematic/lexical verb to raise to C in the formation of questions, as is possible in other languages (cf. Pollack, 1989). This constraint is evident in the ungrammaticality of clauses such as *“where sleeps the bug?” It is important to note that the non-emphatic auxiliary DO in questions is thought to be different from the emphatic DO auxiliaries of matrix non-negated declaratives because the semantics of the declarative context is not evident in the question context. Thus, DO and BE occupants of finiteness in English questions are considered to be structural requirements of grammar mostly free of semantic information. See Figure 4 for an example of the representation of DO auxiliaries in Whquestions (“What does the bug like to eat?”) and Figure 5 for the representation of DO auxiliaries in Yes/no questions (“Does she like to swim?”). Thus, BE and DO forms in questions share the property of finiteness marking in a projection directly related to matrix clause structure. This makes it possible to evaluate children’s emerging knowledge of finiteness marking in linguistic contexts a short step away from simple matrix declarative clauses, involving a projection to the CP beyond the IP. Short summary of finiteness marking in simple matrix clauses of young children with and without SLI The first phase of investigation of children’s knowledge of finiteness marking in simple clauses focused on the early stages of grammatical acquisition of typically developing children. Wexler (1994) formulated an Optional Infinitive account 1 of English-speaking children’s tendency to omit finiteness markers early on. A significant insight of this model is the recognition of the relevance for children’s grammars of the shared property of finiteness marking across different morphemes of English, including the lexical affixes for third person singular present or habitual tense –s, past tense regular –ed or the several irregular past tense morphological variants, auxiliary and copula BE and auxiliary DO. Note that recognition of the shared grammatical properties of these forms does not bring with it the claim that the various forms of finiteness marking are all the same; instead it is recognized that there are obvious differences across these forms as well as the shared property, differences that are likely to influence the ways in which 1The OI model was later updated to the Agreement Tense/Omission Model (Schütze &Wexler, 1996; Wexler, Schütze & Rice, 1998) and the Unique Checking Constraint Model (Wexler, 1998). The updates do not change the analysis of English presented here. Rice et al. Page 4 J Speech Lang Hear Res. Author manuscript; available in PMC 2010 December 1. N IH PA Athor M anscript N IH PA Athor M anscript N IH PA Athor M anscript children master them, although such differences do not over-ride the shared function of finiteness marking (cf Rice, Wexler and Hershberger, 1998, p. 1427). This model was translated to a model of language impairment in the Extended Optional Infinitive (EOI) account, which posited that the elements of the VP likely to be omitted by children with SLI were the finiteness morphemes as in younger typically developing children although the period of omissions persisted for a longer time for the children with SLI. From the outset this has been regarded as an extended developmental model (Rice and Wexler, 1996). A program of investigation of matrix declarative clauses evaluated the predictions of the EOI account. On the normative side, young unaffected English-speaking children are likely to drop finiteness morphemes until approximately 4 years of age (Rice, Wexler and Cleave, 1995; Rice and Wexler, 1996; Rice, Wexler, and Hershberger, 1998). The pattern is shared by lexical affixes, BE and DO. With regard to affected children, these same studies demonstrated that children with SLI lag behind younger language-equivalent control children, a lag also demonstrated in the emergence of BE and DO in the grammars of younger affected children (Hadley and Rice (1996)). Longitudinal studies found that the lag in affected children persists for years (Rice, Wexler, and Hershberger, 1998; Rice, Tomblin, Hoffman, Richman and Marquis, 2004) and adds support to the interpretation of shared weakness across the set of morphemes across time. Grammaticality judgment tasks established that the phenomenon was not a production limitation. Unaffected, normative control groups showed that children were likely to accept matrix clauses with missing finiteness marking as grammatical until around 4;6–5;0 years, a pattern that persisted through 8 years for children with SLI (Rice, Wexler and Redmond, 1999). It is noteworthy that the SLI group’s mean performance was not at ceiling for omitted finiteness at the last time of measurement, suggesting that the grammaticality judgment format would be suitable for extension to older ages of assessment if the linguistic context were more challenging. Rice (2003; 2004; 2007) interprets the longitudinal outcomes as a disrupted grammatical trajectory in which finiteness markers are weaker than other elements of the grammar, even when adjusted for a late onset. A replicated finding in these studies, for both production and judgment tasks, is that performance on finiteness marking tasks is not predicted by the children’s nonverbal IQ, receptive vocabulary or mother’s education, for either the affected children or the comparison groups. This supports the interpretation that the requirement for finiteness marking is largely independent of vocabulary and that grammatical competence or limitations in this domain are not accounted for by general intellectual development. Cross-sectional studies replicate the generalization that young children with SLI, as a group, are likely to perform less accurately than younger controls on morphemes associated with the finiteness marker. The bulk of the evidence for this generalization comes from children ages 4 to 8 years (cf. Bedore and Leonard, 1998; Conti-Ramsden, Botting, and Faragher, 2001; Eadie, Fey, Douglas, and Parsons, 2002; Grela and Leonard, 2000; Joseph, Serratrice, and Conti-Ramsden, 2002; Leonard, Eyer, Bedore and Grela; Marchman, Wulfeck, and Ellis Weismer, 1999; Oetting and Horohov, 1997). More recent studies document the predicted lag at onset in the 24–36-month age range (Hadley and Holt, 2006; Hadley and Short, 2005). All told, there is solid evidence for the omission of finiteness morphology in English simple declarative clauses as a clinical marker (cf. Rice and Wexler, 2001), evidence that aligns with the grammatical model sketched above. A few studies extend the evidence to complex clauses within this age range (Schuele and Dykes, 2005; Owen and Leonard, 2006). Although debate continues about the underlying source of the grammatical weakness, the basic phenomenon of shared weakness is empirically robust for the ages of children studied to date, for the available tasks and assessments. At the same time, the declarative clause contexts appropriate for this age range are less sensitive to affectedness by around 8 years for affected children. Rice et al. Page 5 J Speech Lang Hear Res. Author manuscript; available in PMC 2010 December 1. N IH PA Athor M anscript N IH PA Athor M anscript N IH PA Athor M anscript Clinical markers for elementary school aged children with SLI Following the model of functional projections described above, a related consequence of omitted finiteness marking in IP projections in young children could be a tolerance for omitted finiteness marking in the CP projections in the grammars of older children. If affected children continue to trail unaffected children in their growth patterns, as we expect, then finiteness marking in questions is a likely clinical marker. Two forms of questions are used frequently by children, the yes/no and whquestions illustrated above. Previous studies have examined young unaffected children’s acquisition of yes/no and wh-questions in the context of the movement of copula and auxiliary BE forms from I to C, known as subject/auxiliary inversion (SAI). Guasti (2002) provides a review and concludes that SAI may be optional for preschool children, although by school age unaffected children are able to generate questions with SAI. These studies have focused on the movement requirements of CP projections. It is generally thought that the movement from I to C requires additional computational complexity that leads to later acquisition of questions relative to declaratives. The issue of possible lingering acceptance of omitted forms of BE and DO in questions has not been directly examined as part of the earlier studies, although a persistent weakness in the obligatory properties of TNS/AGR marking is likely to affect the acquisition of questions. There are hints of the usefulness of yes/no questions as markers for language impairment in the production tasks for DO auxiliaries in Rice, Wexler and Hershberger (1998) and also in data reported for the Rice/Wexler Test of Early Grammatical Impairments (Rice and Wexler, 2001). This test data reports that a large proportion (82%) of the language impaired group of 50 children ages 8;00–8;11 (the oldest group sampled) scored at or below 91% accuracy (p. 123 of the examiner’s manual which reports a sensitivity of .82). This is compared to a large proportion (72%) of the control group of 50 children at age 6;06–6;11 (the oldest control age group sampled) who scored above the same level (91%) (p. 122 of the examiner’s manual which reports a specificity of .72)). Thus there was little overlap of the affected group’s performance with the performance levels of children about 2 years younger, suggesting a significant off-set in the growth trajectory for DO auxiliaries in questions. In a recent study of school age children learning English as a second language compared to a group of children with SLI and a control group of unaffected children, levels of production of DO auxiliaries were lower than BE auxiliaries for all three groups of children (Paradis, Rice, Crago and Marquis, 2008). It may be that the extra difficulty of adding a morpheme (DO) that doesn’t occur in the declarative form creates some difficulty for children as they develop language. In this same study, BE copulas and auxiliaries in question contexts were more likely to be omitted by children with SLI than the same forms in declarative sentences, adding further evidence in support of CP projection as a potential grammatical marker of finiteness weakness. Finally, the earlier longitudinal study of grammaticality judgment tasks comprised of simple matrix clauses with omitted finiteness markers reported by Rice, Wexler and Redmond (1999) offers further indication of lingering weakness in judgments of finiteness omission. The tasks involved judgments of sentences such as “he drinks milk” versus “*he eat toast” and “he is hiding” versus “*he running away” (Following linguistic conventions, the * indicates ungrammatical items.) In that study, the SLI group at the last time of measurement at age 8 years were below ceiling performance on these tasks, with average A’ scores of .82 for affected children, as compared to .88 for children two years younger. The study reported here followed the earlier study of Rice, Wexler and Redmond (1999) with investigation of grammaticality judgments of BE copula and auxiliaries and DO auxiliaries in single-clause whand yes/no questions, to evaluate the following questions: Rice et al. Page 6 J Speech Lang Hear Res. Author manuscript; available in PMC 2010 December 1. N IH PA Athor M anscript N IH PA Athor M anscript N IH PA Athor M anscript 1. Will children with SLI who have a documented early history of an EOI period continue to show optional finiteness marking in their willingness to accept omitted BE/DO in questions for a prolonged time? If so, what will be the length of this time? 2. Do affected children outgrow the deficit in finiteness marking or does it persist? Are the growth rates similar for affected and control children throughout the observed time, leading to a persistent gap, or is the affected group able to accelerate growth in order to close the gap? Are the linear and non-linear growth parameters similar in affected and control groups or is there a group X time interaction? 3. Will Whand yes/no questions show similar patterns of growth in grammaticality judgments of finiteness marking over time? 4. Will DO auxiliaries show lower levels of performance than BE forms in questions, with a persistent gap in growth relative to BE? Will the difference be observed for the SLI group only (in a stage of acquisition less mature than the LM group), or for both groups? 5. Will indices of nonverbal IQ, vocabulary, mean length of utterance, and mother’s education at the outset predict growth in question finiteness judgments? Does earlier performance on judgments of omitted finiteness in simple matrix clauses predict growth in question finiteness judgments?