Assessing Sentence Diversity in Toddlers At-Risk for Language Disorders Purpose: The purpose of this article is to introduce clinicians to an approach for assessing toddlers' sentence diversity and using criterion-referenced expectations to identify toddlers at-risk for clinically significant delays in grammatical development between 30 and 36 months of age. Method: Five at-risk toddlers were identified from an ... Article
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Article  |   November 01, 2014
Assessing Sentence Diversity in Toddlers At-Risk for Language Disorders
Author Affiliations & Notes
  • Megan M. McKenna
    Addison School District 4, Addison, IL
    Speech & Language Professionals, Inc., Lake Hills, IL
  • Pamela A. Hadley
    Department of Speech and Hearing Sciences, University of Illinois at Urbana-Champaign, Champaign, IL
  • Financial Disclosure: Megan M. McKenna is a speech-language pathologist at Addison School District 4. Pamela A. Hadley is an associate professor at the University of Illinois at Urbana-Champaign. This study was supported by BCS-0822513, NSF awarded to Matthew Rispoli and Pamela Hadley. This article is based upon Megan McKenna's master's thesis, completed as a graduate student at the University of Illinois.
    Financial Disclosure: Megan M. McKenna is a speech-language pathologist at Addison School District 4. Pamela A. Hadley is an associate professor at the University of Illinois at Urbana-Champaign. This study was supported by BCS-0822513, NSF awarded to Matthew Rispoli and Pamela Hadley. This article is based upon Megan McKenna's master's thesis, completed as a graduate student at the University of Illinois.×
  • Nonfinancial Disclosure: Megan M. McKenna has no nonfinancial interests related to the content of this article. Pamela A. Hadley has previously published in the subject area.
    Nonfinancial Disclosure: Megan M. McKenna has no nonfinancial interests related to the content of this article. Pamela A. Hadley has previously published in the subject area.×
Article Information
Language Disorders / Articles
Article   |   November 01, 2014
Assessing Sentence Diversity in Toddlers At-Risk for Language Disorders
SIG 1 Perspectives on Language Learning and Education, November 2014, Vol. 21, 159-172. doi:10.1044/lle21.4.159
SIG 1 Perspectives on Language Learning and Education, November 2014, Vol. 21, 159-172. doi:10.1044/lle21.4.159

Purpose: The purpose of this article is to introduce clinicians to an approach for assessing toddlers' sentence diversity and using criterion-referenced expectations to identify toddlers at-risk for clinically significant delays in grammatical development between 30 and 36 months of age.

Method: Five at-risk toddlers were identified from an archival database. Mean length of utterance (MLU), grammatical complexity, and sentence diversity measures at 30 months of age were then used to evaluate the grammatical abilities of the at-risk children.

Results: Three participants had MLUs of 1.50 or more standard deviations below the mean which alone would be sufficient for raising clinical concern. Although the other two toddlers had MLUs above 1.50, assessment of sentence diversity identified them as at-risk. The sentence diversity findings were also consistent with low grammatical complexity scores.

Discussion: The clinical usefulness of a sentence-focused approach for assessment, intervention planning, and progress monitoring are discussed.

Assessing Sentence Diversity in Toddlers At-Risk for Language Disorders
Major changes in children's grammatical development occur between the ages of 18 and 30 months, as children learning English transition from single words and first word combinations to diverse childlike sentences with emerging evidence of tense and agreement marking (Hadley, Rispoli, Holt, Fitzgerald, & Bahnsen, 2014; Hadley & Short, 2005; Rispoli, Hadley, & Holt, 2009). Rispoli and Hadley (2011)  proposed that diverse, novel sentences provide evidence of children's ability to produce sentences via grammatical encoding. Grammatical encoding refers to the translation of messages into language through the processes of lexical selection and sentence assembly (Bock & Levelt, 1994; Levelt, 1989). Sentence diversity also creates opportunities to incorporate the full diversity of tense and agreement morphemes into sentence production.
Despite the importance of sentence diversity to grammatical development, expectations for sentence diversity are not readily available to guide clinical practice during this early period of grammatical development. Existing clinical methods, such as Language Assessment and Remediation Screening Procedure (LARSP; Crystal, Fletcher, & Garman, 1976) and the Index of Productive Syntax (IPSyn; Scarborough, 1990), assess numerous syntactic structures emerging between the ages of 2 and 4, making their focus too broad for the fine-grained assessment needed to characterize the emergence of childlike sentences, develop objectives, and measure progress in this early period. Although analysis of semantic relations (Bloom & Lahey, 1978; Retherford, 1987) focuses on early language development, such approaches do not provide an explanation of how semantic combinations become re-organized into an adult-like, syntactically-based grammar (Ingram, 1989), nor are developmental expectations from normative databases available for quantifying the severity of delays in the onset of prevalent semantic relations.
In this article, we present a clinically-useful approach for assessing sentence diversity. The approach focuses specifically on the emergence of childlike sentences. We also report on the application of this approach in a database of 40 typically developing children providing clinicians with developmental expectations for sentence diversity and a means to quantify the severity of delays in early grammatical development at 30 months of age, compared to children from predominantly college-educated families (McKenna, 2013). We then present a retrospective analysis of two children with clinically significant grammatical delays at age 3 to document evidence of their limitations in sentence diversity at 30 months.
Our approach to assessing sentence diversity is grounded in Ingram's (1989)  concept of unique syntactic types (see Hadley, 1999  for discussion). Ingram introduced unique syntactic types to characterize the increasing diversity of syntactically-organized word combinations in Brown's (1973)  Late Stage I. Recent adaptations have focused explicitly on sentence diversity, operationally defined as unique combinations of grammatical subjects and lexical verbs (USV) that can fit into the phrase structure of a more grammatically complete adult utterance (Bahnsen, 2011; Hadley, 2006; McKenna, 2011, 2013; Villa, 2010). For example, the sentences in (1) were produced by a 30-month-old child in 105 complete and intelligible utterances during 10 min of conversational free play with his mother. The sentences are relatively long, but the grammatical subjects are predominantly I.
(1) (I wanna try) I wanna try apple. → I want
I wanna try that.
I want try hotdog?
I don't like taco.          → I like
I don't like taco.
I don't like rice.
I wanna take pizza.
(ooh ma* ooh) mama eat the carrot. → mama eat
and that's go top.         → that go
I wanna take pizza.
Yeah, I take pizza.         → I take
(uh) I wanna go play puzzle.
I blow bubble?           → I blow
I wanna try lion.
I don't want that.
I got!               → I got
I got it!
I got.
(I want) I want do that.
I want to eat.
(uh) I wanna try pizza.
(I want) I want milk.
Cname try pizza.          → Cname try = Child uses own name as subject
I wanna try pizza.
To be identified as a USV, a child's sentence is required to: (a) include an explicit noun or pronoun in the subject noun phrase (NP) position, (b) include a lexical verb, and (c) reflect a sufficiently different subject-verb combination. Lexical variations of subject NPs (e.g., dog/doggy; I/me/Child's name) are treated as a single grammatical subject type. Lexical verbs with different inflected forms, either regular or irregular or catenatives, are treated as a single lexical verb type (e.g., go/going/gonna, get/got, want/wants/wanna). Applying this operational definition to the sentences above, eight subject-verb combinations are unique.
Hadley (1999)  and McKenna (2013)  evaluated the validity of diversity measures relative to traditional measures of utterance length and grammatical complexity in samples of toddlers at-risk for specific language impairment (SLI) and typically developing toddlers. Correlations of the diversity measures with mean length of utterance (MLU; Brown, 1973; Miller & Chapman, 1981) and index of productive syntax (IPSyn) were significant. Hadley (1999)  also found that syntactic diversity was significantly related to grammatical complexity 6-months later (i.e., IPSyn) whereas MLU was not in a sample of toddlers at-risk for SLI. McKenna (2013)  found that sentence diversity, but not MLU, was related to grammatical complexity for 20 typically developing children with MLUs less than 3.25 at 30 months of age. These findings indicate that as children's utterances get longer and more complex in typical development, they also get more diverse, and measures of combinatorial diversity may be better indicators of early grammatical development than MLU when the range of MLU is restricted.
Our sentence diversity approach has also revealed interesting patterns of developmental change (McKenna, 2013; Villa, 2010). First, we have found the frequency of unique subject-verb combinations increases between 21 and 30 months of age, with toddlers producing approximately one per minute by 30 months of age. Second, we have observed a developmental sequence of subject type expansion. Unique combinations with first person subjects (e.g., I have juice, I get puzzles) appear before unique combinations with third person singular subjects (e.g., he want juice; baby got soap), followed by those with second person and plural subjects (e.g., you have this one, we can build a tower, those look like pumpkins). To provide criterion-referenced developmental expectations, McKenna also established cut-off criteria for unique subject-verb combinations, identifying the minimum number of combinations produced by 80% and 90% of the children (Dollaghan, 2007). The bottom 20% produced 6 or fewer unique combinations with first person singular subjects, 5 or fewer with third person singular subjects, and 18 or fewer total unique subject-verb combinations.
The purpose of this article is to apply the assessment of sentence diversity to toddlers at-risk for language disorders. Limited sentence structure is one of the core diagnostic features of a language disorder (American Psychiatric Association, 2013) and limited sentence diversity may hinder the subsequent acquisition of tense and agreement marking (Hadley, 2006; Rispoli & Hadley, 2011). Therefore, in this retrospective study, we expected to observe limited sentence diversity at 30 months of age for children who demonstrated difficulty producing simple sentences marked accurately for tense and agreement at age 3.
Method
Database
Data for the current study was obtained from an existing longitudinal database of 58 children (Rispoli & Hadley, 2008). The database consisted of information from questionnaires about children's general health and family demographics, parent report measures, 30-min parent-child and examiner-child language samples from 21 to 36 months of age, and formal language testing at 36 months of age. None of the children had congenital or acquired brain injury, sensory impairments, repeated bouts of otitis media, pressure equalization tubes, or delayed onset of walking or talking. All children were from homes where English was the only spoken language.
Complete longitudinal records were available for 50 children, with attrition of 8 children over the 15 months (i.e., n=2 after 21 months, n=3 after 30 months, n=1 after 33 months, n=2 only one 36-month session). Thirteen children retained to at least 30 months were identified as at-risk based on parent report of early communication and language abilities, limited intelligibility at 30 months, and/or a history of early intervention services or referral before 36 months. Six of these children failed the communication section of the Ages and Stages Questionnaire (ASQ; Bricker & Squires, 1999) at 21 and/or 24 months; five also scored less than the 10th percentile on the MacArthur-Bates Communicative Development Inventories (CDI; Fenson et al., 2007) at 24 months. Four children received or were referred to independent early intervention services. At 30 months of age, three additional children were identified as at-risk, two because of ongoing concerns about limited intelligibility (i.e., less than 50% of speech understood by unfamiliar adult) and one because of CDI scores falling below the 10th percentile, co-occurring with emerging evidence of stuttering-like dysfluencies.
Participants
Fifteen participants (11 at-risk, 3 typically developing) who had not been included in McKenna's (2013)  study of developmental expectations for sentence diversity and had complete records through 36 months were considered. Two children with characteristics consistent with other conditions (e.g., social communication disorder/autism, stuttering) were excluded because of our primary interest in sentence diversity as an early measure of the grammatical deficits associated with risk for SLI. To be included, children were required to demonstrate clinically significant delays in grammatical knowledge on the Test of Early Grammatical Impairment (TEGI; Rice & Wexler, 2001) at 36 months of age demonstrated by scores less than or equal to the language-disordered mean on two or more of the following probes: (a) the third person singular probe (≤ 29%), past tense probe (≤ 36%), or Be score (i.e., ≤ 23%), or (b) if they were unable to produce scorable responses in the presence of sufficient phonological abilities to produce mark tense and agreement (i.e., passing score on the TEGI's phonological probe). Five children (3 at-risk, 2 typically developing) were not included because of age appropriate grammatical abilities at 36 months and three children (all at-risk) because of insufficient phonological abilities.
Five children (all male) were identified as at-risk for SLI. Three children had difficulty producing scorable responses. One produced scorable responses on the third person singular and past tense probes, but did not produce any correct tense morphemes for either probe (0%). The final participant produced scorable responses for three probes, all well below the cut-off scores for identification of language impairment (i.e., 0%, third person singular, 7% past, 17% BE).
All five children had 30-month CDI scores at or above the 10th percentile reducing the possibility that limited sentence diversity could be attributed to global delays in vocabulary development. All five toddlers were from white families. Their mothers' highest educational levels included completion of high school (n = 2), bachelor's degree (n = 2), and advanced degree (n = 1). The children in McKenna's (2013)  study of developmental expectations for sentence diversity were drawn from primarily white, college educated homes (approximately 75%).
Procedures
The parent-child language samples obtained at 30 months of age provided the primary data for the retrospective language sample analyses. Parent-child language samples were used because this matched the sampling context of existing reference databases for measures of utterance length and grammatical complexity (i.e., MLU, IPSyn) and because a toddler's best language performance is typically observed with their most familiar conversational partners. Children were audio and video recorded with a parent for 30-min and instructed to “play as they would at home” with age-appropriate toys. Toys sets available for children to choose from included a kitchen area with table and chairs, cupboard, dishes, pretend food, stove, and sink, two babies and a highchair, stroller, crib, and bathtub, puzzles, windup toys, blocks, and Mr. Potatohead. Language samples were transcribed and coded following the conventional procedures using Systematic Analysis of Language Transcripts (SALT; Miller & Iglesias, 2010). For further details, interested readers are referred to Hadley et al. (2014) .
Traditional Measures
The total number of utterances and number of complete and intelligible utterances were calculated on the entire 30-min language sample. MLU scores were computed on 100 complete and intelligible utterances, excluding yes/no responses to parent questions1 . For children with MLUs >1.50, grammatical complexity was further analyzed with the IPSyn using the same sample of 100 complete and intelligible utterances. Further analysis was warranted given that MLU often overestimates the grammatical complexity of children with language impairments (see Eisenberg, McGovern Fersko, & Lundgren, 2001  for review).
Sentence Diversity Measures
For children with MLUs >1.50, sentence diversity was also analyzed using all complete and intelligible utterances from the full 30-min sample. Child sentences had to include both an explicit subject and a lexical verb. Sentences with copula BE as its main verb or copula BE omissions were not included. Utterances that consisted of routine expressions from songs, stories, or games, imitations of prior adult utterances, and partially intelligible utterances were not coded.
Each sentence subject was also coded for its features of person (i.e., first, second, third) and number (i.e., singular, plural): [SV:1] for first person singular subjects (i.e., I, me, my, child's own name); [SV:2] for second person singular subjects (e.g., you); [SV:3] for third person singular lexical (e.g. baby, Pooh) or pronominal (e.g. it, he, she) subjects; [SV:1P] for first person plural subjects (e.g., we); and [SV:3P] for third person plural lexical (e.g., blocks, bubbles) and pronominal (i.e., they) subjects. Coding of sentences with each subject type is provided in (2).
(2) Me[SV:1] do it.
You[SV:2] have this one.
Baby[SV:3] eat it.
We[SV:1P] can build a tower.
Those[SV:3P] look like pumpkins.
Two additional codes, [SV:P] and [SV:RQ], were used to identify sentences that may not have true subjects or that may not be produced via grammatical encoding (Rispoli & Hadley, 2011). An [SV:P] code was applied to combinations with names of conversation partners in the subject position (e.g., Mommy/Daddy blow bubble). Partner names had the potential to be addressee terms rather than subjects and so were eliminated from further analysis. An [SV:RQ] code was applied to subjects of the routine do/go questions (e.g., where doggie[SV:RQ] go?), as these question forms have the potential to be formulaic (Miller & Chapman, 1981).
All coded sentences were extracted from the language samples to determine the number of unique subject-verb (USV) combinations. The coded sentences reflect tokens of subject-verb combinations. The number of USVs reflects types of subject-verb combinations. To illustrate this, the tokens and types of a typically developing toddler (Child 1) are presented in Appendix A. The process of reducing all coded sentences to determine the number of USVs for each subject type and USV total is illustrated. Compared to our reference data provided in Table 1, Child 1 shows average sentence diversity and a typical pattern of subject type expansion. As can be seen, Child 1 produced the most unique combinations with first person subjects, seven with third person subjects, and a few with other sentence subjects (i.e., second person and plural). The number of unique subject-verb combinations with first person subjects, third person subjects and all unique combinations fall within the average range. Note also the increasing grammatical complexity in utterances such as elaborated subject noun phrases (e.g., the farmer), correct case-marked subject pronouns (i.e., he, we), and the appearance of early tense and agreement markers (e.g., 'm, is). At the same time Child 1's sentences became more diverse, his utterances increased in length and became more grammatically complex. Relative to peers, Child 1 had expressive vocabulary in the average range at 24 and 30 months (CDI percentile ranks = 60th and 45th, respectively), and his utterance length and grammatical complexity were in the average range at 30 months as well (MLU = 2.47, MLU z = -.01; IPSyn = 63; IPSyn z = 0.40).
Table 1 Frequency of Total Subject-Lexical Verb Combinations and USVs from McKenna (2013) .
Frequency of Total Subject-Lexical Verb Combinations and USVs from McKenna (2013) .×
Subject-Lexical Verb Combinations (tokens)
USVs (types)
[SV:1] [SV:2] [SV:3] [SV:1P] [SV:3P] USV1 USV3 USV Other USV Total
Min 5 0 2 0 0 4 2 0 11
Max 115 38 67 24 12 17 36 2 76
Mean 30.53 8.7 14.28 3.38 1.83 10.70 9.70 7.83 28.23
SD 22.45 7.95 11.78 4.54 2.75 3.86 6.39 6.63 13.83
Note. ID = Participant identification number; [SV:1] = subject-verb (SV) combinations with a first person singular subject; [SV:2] = SV combinations with a second person subject; [SV:3] = SV combinations with a third person singular subject; [SV:1P] = SV combinations with a first person plural subject; [SV:3P] = SV combinations with a third person plural subject; USV-1 = Number of unique subject-verbs combinations (USVs) with first person singular subjects; USV-3 = Number of USVs with third person singular subjects; USV Other = Number of USVs with second person, first person plural, and third person plural subjects combined; USV Total = Number of total USVs of all sentence subject types. N = 40
Note. ID = Participant identification number; [SV:1] = subject-verb (SV) combinations with a first person singular subject; [SV:2] = SV combinations with a second person subject; [SV:3] = SV combinations with a third person singular subject; [SV:1P] = SV combinations with a first person plural subject; [SV:3P] = SV combinations with a third person plural subject; USV-1 = Number of unique subject-verbs combinations (USVs) with first person singular subjects; USV-3 = Number of USVs with third person singular subjects; USV Other = Number of USVs with second person, first person plural, and third person plural subjects combined; USV Total = Number of total USVs of all sentence subject types. N = 40×
Table 1 Frequency of Total Subject-Lexical Verb Combinations and USVs from McKenna (2013) .
Frequency of Total Subject-Lexical Verb Combinations and USVs from McKenna (2013) .×
Subject-Lexical Verb Combinations (tokens)
USVs (types)
[SV:1] [SV:2] [SV:3] [SV:1P] [SV:3P] USV1 USV3 USV Other USV Total
Min 5 0 2 0 0 4 2 0 11
Max 115 38 67 24 12 17 36 2 76
Mean 30.53 8.7 14.28 3.38 1.83 10.70 9.70 7.83 28.23
SD 22.45 7.95 11.78 4.54 2.75 3.86 6.39 6.63 13.83
Note. ID = Participant identification number; [SV:1] = subject-verb (SV) combinations with a first person singular subject; [SV:2] = SV combinations with a second person subject; [SV:3] = SV combinations with a third person singular subject; [SV:1P] = SV combinations with a first person plural subject; [SV:3P] = SV combinations with a third person plural subject; USV-1 = Number of unique subject-verbs combinations (USVs) with first person singular subjects; USV-3 = Number of USVs with third person singular subjects; USV Other = Number of USVs with second person, first person plural, and third person plural subjects combined; USV Total = Number of total USVs of all sentence subject types. N = 40
Note. ID = Participant identification number; [SV:1] = subject-verb (SV) combinations with a first person singular subject; [SV:2] = SV combinations with a second person subject; [SV:3] = SV combinations with a third person singular subject; [SV:1P] = SV combinations with a first person plural subject; [SV:3P] = SV combinations with a third person plural subject; USV-1 = Number of unique subject-verbs combinations (USVs) with first person singular subjects; USV-3 = Number of USVs with third person singular subjects; USV Other = Number of USVs with second person, first person plural, and third person plural subjects combined; USV Total = Number of total USVs of all sentence subject types. N = 40×
×
Results
Table 2 presents descriptive data for the five at-risk participants at 30 months of age, including CDI total words, CDI percentile rank, number of complete and intelligible utterances, and MLU and IPSyn scores. For three participants, MLUs were more than 1.50 standard deviations below 30 month expectations (M = 2.54; SD = 0.57; Miller & Chapman, 1981). Further analysis of sentence diversity would not likely be necessary to identify these children as at-risk. In contrast, two children had MLUs above 1.50. In these cases, further analysis of sentence diversity and grammatical complexity was warranted.
Table 2 At-Risk Participants' Language Measures.
At-Risk Participants' Language Measures.×
Database ID / Child TEGI CDI CDI PR C&I Utts MLU MLU z IPSyn IPSyn z SV:1 SV:3 SV:O USV1 USV3 USVO USV Total
GTP04B 0% 218 10 99 1.37 -2.05
GTP15B NA 373 25 28 1.46 -1.89
GTP16B NA 259 10 100 1.25 -2.26
GTP22B Child 2 8% 246 10 100 2.62 0.14 41 -1.67 62 2 3 15 2 2 19
GTP52B Child 3 NA 349 20 100 1.78 -1.33 34 -2.32 3 4 1 3 3 1 7
Note. ID = Participant identification number; TEGI = Average accuracy score on probes completed on the Test of Early Grammatical Impairment; CDI = Total vocabulary on the MacArthur-Bates Communicative Development Inventories (CDI); CDI PR = CDI percentile rank; C&I Utts = Number of complete and intelligible utterances; MLU = Mean length of utterance in morphemes; MLU z = MLU z-score; IPSyn = Index of Productive Syntax score; IPSyn z = IPSyn z-score; SV:1 = Subject-verb combinations with first person singular subjects; SV:3 = Subject-verb combinations with third person singular subjects; SV:O = Subject-verb combinations with other subjects, including second person, first person plural, and/or third person plural subjects; USV1 = Number of unique subject-verbs combinations (USVs) with first person singular subjects; USV3 = Number of USVs with third person singular subjects; USV Other = Number of USVs with second person, first person plural, and third person plural subjects combined; USV Total = Number of total USVs of all sentence subject. N = 5
Note. ID = Participant identification number; TEGI = Average accuracy score on probes completed on the Test of Early Grammatical Impairment; CDI = Total vocabulary on the MacArthur-Bates Communicative Development Inventories (CDI); CDI PR = CDI percentile rank; C&I Utts = Number of complete and intelligible utterances; MLU = Mean length of utterance in morphemes; MLU z = MLU z-score; IPSyn = Index of Productive Syntax score; IPSyn z = IPSyn z-score; SV:1 = Subject-verb combinations with first person singular subjects; SV:3 = Subject-verb combinations with third person singular subjects; SV:O = Subject-verb combinations with other subjects, including second person, first person plural, and/or third person plural subjects; USV1 = Number of unique subject-verbs combinations (USVs) with first person singular subjects; USV3 = Number of USVs with third person singular subjects; USV Other = Number of USVs with second person, first person plural, and third person plural subjects combined; USV Total = Number of total USVs of all sentence subject. N = 5×
Table 2 At-Risk Participants' Language Measures.
At-Risk Participants' Language Measures.×
Database ID / Child TEGI CDI CDI PR C&I Utts MLU MLU z IPSyn IPSyn z SV:1 SV:3 SV:O USV1 USV3 USVO USV Total
GTP04B 0% 218 10 99 1.37 -2.05
GTP15B NA 373 25 28 1.46 -1.89
GTP16B NA 259 10 100 1.25 -2.26
GTP22B Child 2 8% 246 10 100 2.62 0.14 41 -1.67 62 2 3 15 2 2 19
GTP52B Child 3 NA 349 20 100 1.78 -1.33 34 -2.32 3 4 1 3 3 1 7
Note. ID = Participant identification number; TEGI = Average accuracy score on probes completed on the Test of Early Grammatical Impairment; CDI = Total vocabulary on the MacArthur-Bates Communicative Development Inventories (CDI); CDI PR = CDI percentile rank; C&I Utts = Number of complete and intelligible utterances; MLU = Mean length of utterance in morphemes; MLU z = MLU z-score; IPSyn = Index of Productive Syntax score; IPSyn z = IPSyn z-score; SV:1 = Subject-verb combinations with first person singular subjects; SV:3 = Subject-verb combinations with third person singular subjects; SV:O = Subject-verb combinations with other subjects, including second person, first person plural, and/or third person plural subjects; USV1 = Number of unique subject-verbs combinations (USVs) with first person singular subjects; USV3 = Number of USVs with third person singular subjects; USV Other = Number of USVs with second person, first person plural, and third person plural subjects combined; USV Total = Number of total USVs of all sentence subject. N = 5
Note. ID = Participant identification number; TEGI = Average accuracy score on probes completed on the Test of Early Grammatical Impairment; CDI = Total vocabulary on the MacArthur-Bates Communicative Development Inventories (CDI); CDI PR = CDI percentile rank; C&I Utts = Number of complete and intelligible utterances; MLU = Mean length of utterance in morphemes; MLU z = MLU z-score; IPSyn = Index of Productive Syntax score; IPSyn z = IPSyn z-score; SV:1 = Subject-verb combinations with first person singular subjects; SV:3 = Subject-verb combinations with third person singular subjects; SV:O = Subject-verb combinations with other subjects, including second person, first person plural, and/or third person plural subjects; USV1 = Number of unique subject-verbs combinations (USVs) with first person singular subjects; USV3 = Number of USVs with third person singular subjects; USV Other = Number of USVs with second person, first person plural, and third person plural subjects combined; USV Total = Number of total USVs of all sentence subject. N = 5×
×
Raw data for the two children with MLUs above 1.50 is provided in Appendix A. Child 2 had an MLU of 2.62, with his five longest utterances ranging from 5 to 10 morphemes. Yet, his IPSyn score of 41 placed him 1.67 SD below the 30-month mean. Further analysis of sentence diversity revealed an imbalance of sentences with first person singular versus third person singular subjects. Of his 19 total USVs, 15 were with first person subjects, and some of these included substitution of the child's own name for the first person singular subject pronoun I. Only two USVs contained third person singular subjects and both of these were combined with the all-purpose lexical verb go. Child 3 had a different profile. Despite an MLU of 1.78, his longest utterances were only 3 to 4 morphemes. His IPSyn score of 34 placed him 2.32 SD below the 30-month mean. Although he produced three USVs with third person singular subjects, he produced only 7 total USVs. Compared to McKenna's (2013)  criterion-referenced expectations, both at-risk participants showed limited sentence diversity. In fact, both at-risk participants fell at or in the bottom 10% of the sample of typically developing children for USVs with third person singular subjects (see Table 3).
Table 3 Norm-referenced and Criterion-referenced Sentence Diversity Cut-offs from McKenna (2013). 
Norm-referenced and Criterion-referenced Sentence Diversity Cut-offs from McKenna (2013). ×
USV-1 USV-3 USV Total
Mean 10.70 9.70 28.23
(SD) (3.86) (6.39) (13.83)
Normal distribution cut-off
 -1.25 SD below mean 5.88 1.71 10.94
Criterion-referenced cut-off
 80% cut-off 6 5 18
 90% cut-off 5 3 12
Typically-developing toddler
 Child 1 15 7 28
At-risk participant scores
 Child 2 15 2 19
 Child 3 3 3 7
Note. USV-1 = First person singular unique subject-verb combinations (USVs); USV-3 = Third person singular USVs; USV Total = All USVs.
Note. USV-1 = First person singular unique subject-verb combinations (USVs); USV-3 = Third person singular USVs; USV Total = All USVs.×
Table 3 Norm-referenced and Criterion-referenced Sentence Diversity Cut-offs from McKenna (2013). 
Norm-referenced and Criterion-referenced Sentence Diversity Cut-offs from McKenna (2013). ×
USV-1 USV-3 USV Total
Mean 10.70 9.70 28.23
(SD) (3.86) (6.39) (13.83)
Normal distribution cut-off
 -1.25 SD below mean 5.88 1.71 10.94
Criterion-referenced cut-off
 80% cut-off 6 5 18
 90% cut-off 5 3 12
Typically-developing toddler
 Child 1 15 7 28
At-risk participant scores
 Child 2 15 2 19
 Child 3 3 3 7
Note. USV-1 = First person singular unique subject-verb combinations (USVs); USV-3 = Third person singular USVs; USV Total = All USVs.
Note. USV-1 = First person singular unique subject-verb combinations (USVs); USV-3 = Third person singular USVs; USV Total = All USVs.×
×
Discussion
The purpose of this article was to introduce clinicians to an approach for assessing toddlers' sentence diversity and to determine whether children having difficulties producing simple sentences marked accurately for tense and agreement at 36 months had limited sentence structure at 30 months of age. In this retrospective analysis, three of the five participants with clinically significant grammatical delays at 36 months had clinically significant delays in MLU, and their limited ability to combine words at 30 months would likely raise clinical concern. However, two participants were typically combining words at 30 months with MLUs above 1.50. For these two toddlers, our analysis of sentence diversity revealed limited grammatical abilities, consistent with their low IPSyn scores, demonstrating the clinical usefulness of the sentence diversity analysis approach.
If the IPSyn, an existing measure of syntactic productivity, can be used to identify early grammatical delays at 30 months, why have we developed an alternative measure of sentence diversity? There are several reasons. First, the primary value of the sentence diversity analysis is its explicit focus on childlike sentences as a central developmental accomplishment in the brief, yet critical window, between word combinations and simple, adult sentences marked for tense and agreement (i.e., MLU 1.50-2.50). The IPSyn was designed as a global measure to capture differences between children or changes over relatively long intervals (e.g., 6 to 12 months). As such, it includes assessment of 56 grammatical structures that typically emerge between 2 and 4 years of age. Only two items on the sentence structure subscale are specific to simple sentences, and maximum scores on these items can be obtained with 2 exemplars of a subject-verb-object I-sentence. In other words, the IPSyn may not be sensitive to limitations in sentence diversity for an individual child during this brief developmental period.
Second, the measure of sentence diversity is valid, demonstrating moderate to moderately strong relationships with grammatical complexity as measured by the IPSyn (McKenna, 2013). Although utterance length is also associated with grammatical complexity in typically developing children, MLU often over-estimates the grammatical complexity of children with language impairments and does not effectively identify children with language impairments (Eisenberg et al., 2001; Scarborough, Rescorla, Tager-Flusberg, Fowler, & Sudhalter, 1991). Comparison of Child 1, the typically developing toddler, and at-risk toddler Child 2 in Appendix A, illustrates this point. It is apparent that despite similar MLUs, Child 2's sentence diversity and grammatical complexity are insufficient. Child 2 can string together words (e.g., and taco and rice and hotdog and pizza and pizza) to increase his MLU, but his ability to communicate a variety of diverse messages is limited by his difficulty combining third person singular subjects with lexical verbs. On the other hand, Child 2's limited sentence diversity, especially with third person subjects, was consistent with his low IPSyn score.
Third, the explicit focus on unique combinations of grammatical subjects and lexical verbs makes the measure of sentence diversity simple to compute and interpret for clinical purposes. The results of a sentence diversity assessment can lead directly to goal-writing and treatment plans. Hadley (2014)  discussed participation-based objectives that would support children's production of different combinations of subjects and verbs to produce diverse messages as children take part in meaningful conversations. Expanding the diversity of messages children can express by targeting diverse sentence combinations is more functional than goals designed to increase utterance length alone. Goals and therapy activities designed to move at-risk toddlers like Child 2 from I-sentences to sentences with third person subjects with singular then plural subjects would also support his successful transition to more literate language use. For Child 3, increasing the number of I-sentences with diverse lexical verbs would be a developmental priority before sentences with third person subjects.
Finally, this measure of sentence diversity can be computed efficiently using structure-specific sampling for purposes of monitoring progress (Hadley, 1999; 2006). For children with limited sentence diversity, a clinician should be able to record new combinations of subjects and verbs in real time. Data collection would consist of listening strategically for word combinations that included explicit subjects and lexical verbs during a portion of a therapy session or when observing parent-toddler interaction. Following the session, this list would be reduced to document change over time in the number of unique combinations [refer to (1)]. Increases in USVs for the targeted sentence subject types would demonstrate quantitative progress in sentence diversity. In summary, assessment of sentence diversity may be particularly useful for children who are combining words on a regular basis (i.e., MLU 1.50–2.50).
From our perspective, the ability to produce diverse childlike sentences is a central developmental accomplishment in the third year of life. Therefore, sentence diversity is recommended as a standard component of early language assessments. This study has illustrated that children who demonstrated late acquisition of tense and agreement morphemes also had limited sentence diversity at 30 months. Clinicians are encouraged to incorporate sentence diversity analyses into their assessment practices and target production of diverse sentences as part of early intervention for children with language disorders.
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Appendix A
Subject-Verb and Unique Subject-Verb Combinations
Child 1 Child 2 Child 3
SV:1 C (i ha*) i[SV:1] have apple juice. C i[SV:1] wanna try chicken go/ing in. C {hey} i[SV:1] make it.
C i[SV:1] don't know. C {oh oh} i[SV:1] wanna do that. [×2] C i[SV:1] bring pooh/z hin.
C i[SV:1] get the puzzle/s. C and Cname[SV:1] sit right there. C i[SV:1] dunno.
C i[SV:1] don't see any. C (i wanna try) i[SV:1] wanna try apple.
C i[SV:1] have some food right. C i[SV:1] wanna try that.
C but i[SV:1] don't need to cook it. C i[SV:1] want try hotdog?
C i[SV:1] don't see grape/s. C i[SV:1] don't like taco. [×2]
C i[SV:1] don't see grape/s. C i[SV:1] don't like rice.
C i[SV:1] got another hotdog for me. C i[SV:1] wanna take pizza.
C i[SV:1]/'m gonna use this. C yeah|yes, i[SV:1] take pizza.
C i[SV:1] use it right there. C (uh) i[SV:1] wanna go play puzzle.
C i[SV:1] spill that. C i[SV:1] blow bubble?
C i[SV:1] don't know. C i[SV:1] wanna try lion.
C i[SV:1]/'m build/ing block/s. C i[SV:1] don't want that.
C (i see) i[SV:1] see you. C i[SV:1] got! [×2]
C i[SV:1] see you. C i[SV:1] got it!
C i[SV:1] see you. C i[SV:1] want to eat.
C i[SV:1] <see>. C (uh) i[SV:1] wanna try pizza.
C i[SV:1] see you. C (i want) i[SV:1] want milk.
C {oh} i[SV:1] see. C Cname[SV:1] try pizza.
C i[SV:1] want that one. C i[SV:1] wanna try pizza.
C i[SV:1] have this. C no, i[SV:1] try hotdog.
C i[SV:1] don't know. C i[SV:1] don't like pizza.
C i[SV:1]/'m gonna go make you something else. C i[SV:1]/'ll cut.
C i[SV:1] open it for you, ok? C Cname[SV:1] bite.
C i[SV:1] forgot. C i[SV:1] build house.
C but i[SV:1] like (taca) taco/s! C Cname[SV:1] build/ing house.
C can i[SV:1] eat it? C <(i) i[SV:1] see you>.
C (c*) can i[SV:1] eat your pizza? C Cname[SV:1] build tower?
C i[SV:1] got lot of stuff. C i[SV:1] build own.
C i[SV:1] got all this stuff. C Cname[SV:1] cut.
C i[SV:1] got lots : stuff. C (um i want) i[SV:1] gotta put cup back.
C i[SV:1] don't know. C mama, (i want) i[SV:1] want put that.
C i[SV:1] help. C (um) i[SV:1] don't know.
C i[SV:1] don't need my help. C (i) i[SV:1] wanna play with baby.
C (i) i[SV:1] wanna play that.
C i[SV:1] want that. [×7]
C i[SV:1] need this.
C i[SV:1] wanna (try) try cut.
C (uh) i[SV:1] want open the door.
C i[SV:1] want a other baby out.
C (i*) i[SV:1] wanna try. [×2]
C i[SV:1] want juice.
C i[SV:1] want eat. [×2]
C i[SV:1] wanna try that stuff.
C i[SV:1] wash my hand.
C i[SV:1] wanna make a egg.
C i[SV:1] cut. [×2]
C i[SV:1] cut it that.
C i[SV:1] eat now.
SV:2 C and you[SV:2] get the elephant one. C you[SV:2] eat the pizza. C you[SV:2] eat broccoli, ma?
C and you[SV:2] got to blow it.
C you[SV:2] have this one.
C you[SV:2] don't want it?
C <you[SV:2] gotta> use your little finger/s.
SV:3 C (um) something else[SV:3] go. C I wanna try chicken[SV:3] go/ing in. C and chicken[SV:3] make.
C and the farmer[SV:3] can feed the sheep/s. C and that[SV:3]/'s go top. C pizza[SV:3] come/ing, ma.
C he[SV:3] want this apple. C pizza[SV:3] come/ing.
C (ch*) it[SV:3]/'has got cheese. C a knife[SV:3] stir.
C somebody[SV:3]/'s come/ing.
C he[SV:3] got soap.
C he[SV:3] can take a walk.
SV:1P C we[SV:1P] can build a tower now.
C we[SV:1P] gotta buckle him up.
C we[SV:1P] got soap in there.
SV:3P C those[SV:3P] look a bit orangish. C they[SV:3P] eat some more pizza.
C those[SV:3P] look like pumpkin/s.
Child 1 Child 2 Child 3
SV:1 C (i ha*) i[SV:1] have apple juice. C i[SV:1] wanna try chicken go/ing in. C {hey} i[SV:1] make it.
C i[SV:1] don't know. C {oh oh} i[SV:1] wanna do that. [×2] C i[SV:1] bring pooh/z hin.
C i[SV:1] get the puzzle/s. C and Cname[SV:1] sit right there. C i[SV:1] dunno.
C i[SV:1] don't see any. C (i wanna try) i[SV:1] wanna try apple.
C i[SV:1] have some food right. C i[SV:1] wanna try that.
C but i[SV:1] don't need to cook it. C i[SV:1] want try hotdog?
C i[SV:1] don't see grape/s. C i[SV:1] don't like taco. [×2]
C i[SV:1] don't see grape/s. C i[SV:1] don't like rice.
C i[SV:1] got another hotdog for me. C i[SV:1] wanna take pizza.
C i[SV:1]/'m gonna use this. C yeah|yes, i[SV:1] take pizza.
C i[SV:1] use it right there. C (uh) i[SV:1] wanna go play puzzle.
C i[SV:1] spill that. C i[SV:1] blow bubble?
C i[SV:1] don't know. C i[SV:1] wanna try lion.
C i[SV:1]/'m build/ing block/s. C i[SV:1] don't want that.
C (i see) i[SV:1] see you. C i[SV:1] got! [×2]
C i[SV:1] see you. C i[SV:1] got it!
C i[SV:1] see you. C i[SV:1] want to eat.
C i[SV:1] <see>. C (uh) i[SV:1] wanna try pizza.
C i[SV:1] see you. C (i want) i[SV:1] want milk.
C {oh} i[SV:1] see. C Cname[SV:1] try pizza.
C i[SV:1] want that one. C i[SV:1] wanna try pizza.
C i[SV:1] have this. C no, i[SV:1] try hotdog.
C i[SV:1] don't know. C i[SV:1] don't like pizza.
C i[SV:1]/'m gonna go make you something else. C i[SV:1]/'ll cut.
C i[SV:1] open it for you, ok? C Cname[SV:1] bite.
C i[SV:1] forgot. C i[SV:1] build house.
C but i[SV:1] like (taca) taco/s! C Cname[SV:1] build/ing house.
C can i[SV:1] eat it? C <(i) i[SV:1] see you>.
C (c*) can i[SV:1] eat your pizza? C Cname[SV:1] build tower?
C i[SV:1] got lot of stuff. C i[SV:1] build own.
C i[SV:1] got all this stuff. C Cname[SV:1] cut.
C i[SV:1] got lots : stuff. C (um i want) i[SV:1] gotta put cup back.
C i[SV:1] don't know. C mama, (i want) i[SV:1] want put that.
C i[SV:1] help. C (um) i[SV:1] don't know.
C i[SV:1] don't need my help. C (i) i[SV:1] wanna play with baby.
C (i) i[SV:1] wanna play that.
C i[SV:1] want that. [×7]
C i[SV:1] need this.
C i[SV:1] wanna (try) try cut.
C (uh) i[SV:1] want open the door.
C i[SV:1] want a other baby out.
C (i*) i[SV:1] wanna try. [×2]
C i[SV:1] want juice.
C i[SV:1] want eat. [×2]
C i[SV:1] wanna try that stuff.
C i[SV:1] wash my hand.
C i[SV:1] wanna make a egg.
C i[SV:1] cut. [×2]
C i[SV:1] cut it that.
C i[SV:1] eat now.
SV:2 C and you[SV:2] get the elephant one. C you[SV:2] eat the pizza. C you[SV:2] eat broccoli, ma?
C and you[SV:2] got to blow it.
C you[SV:2] have this one.
C you[SV:2] don't want it?
C <you[SV:2] gotta> use your little finger/s.
SV:3 C (um) something else[SV:3] go. C I wanna try chicken[SV:3] go/ing in. C and chicken[SV:3] make.
C and the farmer[SV:3] can feed the sheep/s. C and that[SV:3]/'s go top. C pizza[SV:3] come/ing, ma.
C he[SV:3] want this apple. C pizza[SV:3] come/ing.
C (ch*) it[SV:3]/'has got cheese. C a knife[SV:3] stir.
C somebody[SV:3]/'s come/ing.
C he[SV:3] got soap.
C he[SV:3] can take a walk.
SV:1P C we[SV:1P] can build a tower now.
C we[SV:1P] gotta buckle him up.
C we[SV:1P] got soap in there.
SV:3P C those[SV:3P] look a bit orangish. C they[SV:3P] eat some more pizza.
C those[SV:3P] look like pumpkin/s.
×
1 Removal of yes/no responses to parent questions increased the number of utterances with grammatical constituents in the 100 utterances and reduced the impact of differences in parents' use of yes/no questions on their children's expressive language scores.
Removal of yes/no responses to parent questions increased the number of utterances with grammatical constituents in the 100 utterances and reduced the impact of differences in parents' use of yes/no questions on their children's expressive language scores.×
Table 1 Frequency of Total Subject-Lexical Verb Combinations and USVs from McKenna (2013) .
Frequency of Total Subject-Lexical Verb Combinations and USVs from McKenna (2013) .×
Subject-Lexical Verb Combinations (tokens)
USVs (types)
[SV:1] [SV:2] [SV:3] [SV:1P] [SV:3P] USV1 USV3 USV Other USV Total
Min 5 0 2 0 0 4 2 0 11
Max 115 38 67 24 12 17 36 2 76
Mean 30.53 8.7 14.28 3.38 1.83 10.70 9.70 7.83 28.23
SD 22.45 7.95 11.78 4.54 2.75 3.86 6.39 6.63 13.83
Note. ID = Participant identification number; [SV:1] = subject-verb (SV) combinations with a first person singular subject; [SV:2] = SV combinations with a second person subject; [SV:3] = SV combinations with a third person singular subject; [SV:1P] = SV combinations with a first person plural subject; [SV:3P] = SV combinations with a third person plural subject; USV-1 = Number of unique subject-verbs combinations (USVs) with first person singular subjects; USV-3 = Number of USVs with third person singular subjects; USV Other = Number of USVs with second person, first person plural, and third person plural subjects combined; USV Total = Number of total USVs of all sentence subject types. N = 40
Note. ID = Participant identification number; [SV:1] = subject-verb (SV) combinations with a first person singular subject; [SV:2] = SV combinations with a second person subject; [SV:3] = SV combinations with a third person singular subject; [SV:1P] = SV combinations with a first person plural subject; [SV:3P] = SV combinations with a third person plural subject; USV-1 = Number of unique subject-verbs combinations (USVs) with first person singular subjects; USV-3 = Number of USVs with third person singular subjects; USV Other = Number of USVs with second person, first person plural, and third person plural subjects combined; USV Total = Number of total USVs of all sentence subject types. N = 40×
Table 1 Frequency of Total Subject-Lexical Verb Combinations and USVs from McKenna (2013) .
Frequency of Total Subject-Lexical Verb Combinations and USVs from McKenna (2013) .×
Subject-Lexical Verb Combinations (tokens)
USVs (types)
[SV:1] [SV:2] [SV:3] [SV:1P] [SV:3P] USV1 USV3 USV Other USV Total
Min 5 0 2 0 0 4 2 0 11
Max 115 38 67 24 12 17 36 2 76
Mean 30.53 8.7 14.28 3.38 1.83 10.70 9.70 7.83 28.23
SD 22.45 7.95 11.78 4.54 2.75 3.86 6.39 6.63 13.83
Note. ID = Participant identification number; [SV:1] = subject-verb (SV) combinations with a first person singular subject; [SV:2] = SV combinations with a second person subject; [SV:3] = SV combinations with a third person singular subject; [SV:1P] = SV combinations with a first person plural subject; [SV:3P] = SV combinations with a third person plural subject; USV-1 = Number of unique subject-verbs combinations (USVs) with first person singular subjects; USV-3 = Number of USVs with third person singular subjects; USV Other = Number of USVs with second person, first person plural, and third person plural subjects combined; USV Total = Number of total USVs of all sentence subject types. N = 40
Note. ID = Participant identification number; [SV:1] = subject-verb (SV) combinations with a first person singular subject; [SV:2] = SV combinations with a second person subject; [SV:3] = SV combinations with a third person singular subject; [SV:1P] = SV combinations with a first person plural subject; [SV:3P] = SV combinations with a third person plural subject; USV-1 = Number of unique subject-verbs combinations (USVs) with first person singular subjects; USV-3 = Number of USVs with third person singular subjects; USV Other = Number of USVs with second person, first person plural, and third person plural subjects combined; USV Total = Number of total USVs of all sentence subject types. N = 40×
×
Table 2 At-Risk Participants' Language Measures.
At-Risk Participants' Language Measures.×
Database ID / Child TEGI CDI CDI PR C&I Utts MLU MLU z IPSyn IPSyn z SV:1 SV:3 SV:O USV1 USV3 USVO USV Total
GTP04B 0% 218 10 99 1.37 -2.05
GTP15B NA 373 25 28 1.46 -1.89
GTP16B NA 259 10 100 1.25 -2.26
GTP22B Child 2 8% 246 10 100 2.62 0.14 41 -1.67 62 2 3 15 2 2 19
GTP52B Child 3 NA 349 20 100 1.78 -1.33 34 -2.32 3 4 1 3 3 1 7
Note. ID = Participant identification number; TEGI = Average accuracy score on probes completed on the Test of Early Grammatical Impairment; CDI = Total vocabulary on the MacArthur-Bates Communicative Development Inventories (CDI); CDI PR = CDI percentile rank; C&I Utts = Number of complete and intelligible utterances; MLU = Mean length of utterance in morphemes; MLU z = MLU z-score; IPSyn = Index of Productive Syntax score; IPSyn z = IPSyn z-score; SV:1 = Subject-verb combinations with first person singular subjects; SV:3 = Subject-verb combinations with third person singular subjects; SV:O = Subject-verb combinations with other subjects, including second person, first person plural, and/or third person plural subjects; USV1 = Number of unique subject-verbs combinations (USVs) with first person singular subjects; USV3 = Number of USVs with third person singular subjects; USV Other = Number of USVs with second person, first person plural, and third person plural subjects combined; USV Total = Number of total USVs of all sentence subject. N = 5
Note. ID = Participant identification number; TEGI = Average accuracy score on probes completed on the Test of Early Grammatical Impairment; CDI = Total vocabulary on the MacArthur-Bates Communicative Development Inventories (CDI); CDI PR = CDI percentile rank; C&I Utts = Number of complete and intelligible utterances; MLU = Mean length of utterance in morphemes; MLU z = MLU z-score; IPSyn = Index of Productive Syntax score; IPSyn z = IPSyn z-score; SV:1 = Subject-verb combinations with first person singular subjects; SV:3 = Subject-verb combinations with third person singular subjects; SV:O = Subject-verb combinations with other subjects, including second person, first person plural, and/or third person plural subjects; USV1 = Number of unique subject-verbs combinations (USVs) with first person singular subjects; USV3 = Number of USVs with third person singular subjects; USV Other = Number of USVs with second person, first person plural, and third person plural subjects combined; USV Total = Number of total USVs of all sentence subject. N = 5×
Table 2 At-Risk Participants' Language Measures.
At-Risk Participants' Language Measures.×
Database ID / Child TEGI CDI CDI PR C&I Utts MLU MLU z IPSyn IPSyn z SV:1 SV:3 SV:O USV1 USV3 USVO USV Total
GTP04B 0% 218 10 99 1.37 -2.05
GTP15B NA 373 25 28 1.46 -1.89
GTP16B NA 259 10 100 1.25 -2.26
GTP22B Child 2 8% 246 10 100 2.62 0.14 41 -1.67 62 2 3 15 2 2 19
GTP52B Child 3 NA 349 20 100 1.78 -1.33 34 -2.32 3 4 1 3 3 1 7
Note. ID = Participant identification number; TEGI = Average accuracy score on probes completed on the Test of Early Grammatical Impairment; CDI = Total vocabulary on the MacArthur-Bates Communicative Development Inventories (CDI); CDI PR = CDI percentile rank; C&I Utts = Number of complete and intelligible utterances; MLU = Mean length of utterance in morphemes; MLU z = MLU z-score; IPSyn = Index of Productive Syntax score; IPSyn z = IPSyn z-score; SV:1 = Subject-verb combinations with first person singular subjects; SV:3 = Subject-verb combinations with third person singular subjects; SV:O = Subject-verb combinations with other subjects, including second person, first person plural, and/or third person plural subjects; USV1 = Number of unique subject-verbs combinations (USVs) with first person singular subjects; USV3 = Number of USVs with third person singular subjects; USV Other = Number of USVs with second person, first person plural, and third person plural subjects combined; USV Total = Number of total USVs of all sentence subject. N = 5
Note. ID = Participant identification number; TEGI = Average accuracy score on probes completed on the Test of Early Grammatical Impairment; CDI = Total vocabulary on the MacArthur-Bates Communicative Development Inventories (CDI); CDI PR = CDI percentile rank; C&I Utts = Number of complete and intelligible utterances; MLU = Mean length of utterance in morphemes; MLU z = MLU z-score; IPSyn = Index of Productive Syntax score; IPSyn z = IPSyn z-score; SV:1 = Subject-verb combinations with first person singular subjects; SV:3 = Subject-verb combinations with third person singular subjects; SV:O = Subject-verb combinations with other subjects, including second person, first person plural, and/or third person plural subjects; USV1 = Number of unique subject-verbs combinations (USVs) with first person singular subjects; USV3 = Number of USVs with third person singular subjects; USV Other = Number of USVs with second person, first person plural, and third person plural subjects combined; USV Total = Number of total USVs of all sentence subject. N = 5×
×
Table 3 Norm-referenced and Criterion-referenced Sentence Diversity Cut-offs from McKenna (2013). 
Norm-referenced and Criterion-referenced Sentence Diversity Cut-offs from McKenna (2013). ×
USV-1 USV-3 USV Total
Mean 10.70 9.70 28.23
(SD) (3.86) (6.39) (13.83)
Normal distribution cut-off
 -1.25 SD below mean 5.88 1.71 10.94
Criterion-referenced cut-off
 80% cut-off 6 5 18
 90% cut-off 5 3 12
Typically-developing toddler
 Child 1 15 7 28
At-risk participant scores
 Child 2 15 2 19
 Child 3 3 3 7
Note. USV-1 = First person singular unique subject-verb combinations (USVs); USV-3 = Third person singular USVs; USV Total = All USVs.
Note. USV-1 = First person singular unique subject-verb combinations (USVs); USV-3 = Third person singular USVs; USV Total = All USVs.×
Table 3 Norm-referenced and Criterion-referenced Sentence Diversity Cut-offs from McKenna (2013). 
Norm-referenced and Criterion-referenced Sentence Diversity Cut-offs from McKenna (2013). ×
USV-1 USV-3 USV Total
Mean 10.70 9.70 28.23
(SD) (3.86) (6.39) (13.83)
Normal distribution cut-off
 -1.25 SD below mean 5.88 1.71 10.94
Criterion-referenced cut-off
 80% cut-off 6 5 18
 90% cut-off 5 3 12
Typically-developing toddler
 Child 1 15 7 28
At-risk participant scores
 Child 2 15 2 19
 Child 3 3 3 7
Note. USV-1 = First person singular unique subject-verb combinations (USVs); USV-3 = Third person singular USVs; USV Total = All USVs.
Note. USV-1 = First person singular unique subject-verb combinations (USVs); USV-3 = Third person singular USVs; USV Total = All USVs.×
×
Child 1 Child 2 Child 3
SV:1 C (i ha*) i[SV:1] have apple juice. C i[SV:1] wanna try chicken go/ing in. C {hey} i[SV:1] make it.
C i[SV:1] don't know. C {oh oh} i[SV:1] wanna do that. [×2] C i[SV:1] bring pooh/z hin.
C i[SV:1] get the puzzle/s. C and Cname[SV:1] sit right there. C i[SV:1] dunno.
C i[SV:1] don't see any. C (i wanna try) i[SV:1] wanna try apple.
C i[SV:1] have some food right. C i[SV:1] wanna try that.
C but i[SV:1] don't need to cook it. C i[SV:1] want try hotdog?
C i[SV:1] don't see grape/s. C i[SV:1] don't like taco. [×2]
C i[SV:1] don't see grape/s. C i[SV:1] don't like rice.
C i[SV:1] got another hotdog for me. C i[SV:1] wanna take pizza.
C i[SV:1]/'m gonna use this. C yeah|yes, i[SV:1] take pizza.
C i[SV:1] use it right there. C (uh) i[SV:1] wanna go play puzzle.
C i[SV:1] spill that. C i[SV:1] blow bubble?
C i[SV:1] don't know. C i[SV:1] wanna try lion.
C i[SV:1]/'m build/ing block/s. C i[SV:1] don't want that.
C (i see) i[SV:1] see you. C i[SV:1] got! [×2]
C i[SV:1] see you. C i[SV:1] got it!
C i[SV:1] see you. C i[SV:1] want to eat.
C i[SV:1] <see>. C (uh) i[SV:1] wanna try pizza.
C i[SV:1] see you. C (i want) i[SV:1] want milk.
C {oh} i[SV:1] see. C Cname[SV:1] try pizza.
C i[SV:1] want that one. C i[SV:1] wanna try pizza.
C i[SV:1] have this. C no, i[SV:1] try hotdog.
C i[SV:1] don't know. C i[SV:1] don't like pizza.
C i[SV:1]/'m gonna go make you something else. C i[SV:1]/'ll cut.
C i[SV:1] open it for you, ok? C Cname[SV:1] bite.
C i[SV:1] forgot. C i[SV:1] build house.
C but i[SV:1] like (taca) taco/s! C Cname[SV:1] build/ing house.
C can i[SV:1] eat it? C <(i) i[SV:1] see you>.
C (c*) can i[SV:1] eat your pizza? C Cname[SV:1] build tower?
C i[SV:1] got lot of stuff. C i[SV:1] build own.
C i[SV:1] got all this stuff. C Cname[SV:1] cut.
C i[SV:1] got lots : stuff. C (um i want) i[SV:1] gotta put cup back.
C i[SV:1] don't know. C mama, (i want) i[SV:1] want put that.
C i[SV:1] help. C (um) i[SV:1] don't know.
C i[SV:1] don't need my help. C (i) i[SV:1] wanna play with baby.
C (i) i[SV:1] wanna play that.
C i[SV:1] want that. [×7]
C i[SV:1] need this.
C i[SV:1] wanna (try) try cut.
C (uh) i[SV:1] want open the door.
C i[SV:1] want a other baby out.
C (i*) i[SV:1] wanna try. [×2]
C i[SV:1] want juice.
C i[SV:1] want eat. [×2]
C i[SV:1] wanna try that stuff.
C i[SV:1] wash my hand.
C i[SV:1] wanna make a egg.
C i[SV:1] cut. [×2]
C i[SV:1] cut it that.
C i[SV:1] eat now.
SV:2 C and you[SV:2] get the elephant one. C you[SV:2] eat the pizza. C you[SV:2] eat broccoli, ma?
C and you[SV:2] got to blow it.
C you[SV:2] have this one.
C you[SV:2] don't want it?
C <you[SV:2] gotta> use your little finger/s.
SV:3 C (um) something else[SV:3] go. C I wanna try chicken[SV:3] go/ing in. C and chicken[SV:3] make.
C and the farmer[SV:3] can feed the sheep/s. C and that[SV:3]/'s go top. C pizza[SV:3] come/ing, ma.
C he[SV:3] want this apple. C pizza[SV:3] come/ing.
C (ch*) it[SV:3]/'has got cheese. C a knife[SV:3] stir.
C somebody[SV:3]/'s come/ing.
C he[SV:3] got soap.
C he[SV:3] can take a walk.
SV:1P C we[SV:1P] can build a tower now.
C we[SV:1P] gotta buckle him up.
C we[SV:1P] got soap in there.
SV:3P C those[SV:3P] look a bit orangish. C they[SV:3P] eat some more pizza.
C those[SV:3P] look like pumpkin/s.
Child 1 Child 2 Child 3
SV:1 C (i ha*) i[SV:1] have apple juice. C i[SV:1] wanna try chicken go/ing in. C {hey} i[SV:1] make it.
C i[SV:1] don't know. C {oh oh} i[SV:1] wanna do that. [×2] C i[SV:1] bring pooh/z hin.
C i[SV:1] get the puzzle/s. C and Cname[SV:1] sit right there. C i[SV:1] dunno.
C i[SV:1] don't see any. C (i wanna try) i[SV:1] wanna try apple.
C i[SV:1] have some food right. C i[SV:1] wanna try that.
C but i[SV:1] don't need to cook it. C i[SV:1] want try hotdog?
C i[SV:1] don't see grape/s. C i[SV:1] don't like taco. [×2]
C i[SV:1] don't see grape/s. C i[SV:1] don't like rice.
C i[SV:1] got another hotdog for me. C i[SV:1] wanna take pizza.
C i[SV:1]/'m gonna use this. C yeah|yes, i[SV:1] take pizza.
C i[SV:1] use it right there. C (uh) i[SV:1] wanna go play puzzle.
C i[SV:1] spill that. C i[SV:1] blow bubble?
C i[SV:1] don't know. C i[SV:1] wanna try lion.
C i[SV:1]/'m build/ing block/s. C i[SV:1] don't want that.
C (i see) i[SV:1] see you. C i[SV:1] got! [×2]
C i[SV:1] see you. C i[SV:1] got it!
C i[SV:1] see you. C i[SV:1] want to eat.
C i[SV:1] <see>. C (uh) i[SV:1] wanna try pizza.
C i[SV:1] see you. C (i want) i[SV:1] want milk.
C {oh} i[SV:1] see. C Cname[SV:1] try pizza.
C i[SV:1] want that one. C i[SV:1] wanna try pizza.
C i[SV:1] have this. C no, i[SV:1] try hotdog.
C i[SV:1] don't know. C i[SV:1] don't like pizza.
C i[SV:1]/'m gonna go make you something else. C i[SV:1]/'ll cut.
C i[SV:1] open it for you, ok? C Cname[SV:1] bite.
C i[SV:1] forgot. C i[SV:1] build house.
C but i[SV:1] like (taca) taco/s! C Cname[SV:1] build/ing house.
C can i[SV:1] eat it? C <(i) i[SV:1] see you>.
C (c*) can i[SV:1] eat your pizza? C Cname[SV:1] build tower?
C i[SV:1] got lot of stuff. C i[SV:1] build own.
C i[SV:1] got all this stuff. C Cname[SV:1] cut.
C i[SV:1] got lots : stuff. C (um i want) i[SV:1] gotta put cup back.
C i[SV:1] don't know. C mama, (i want) i[SV:1] want put that.
C i[SV:1] help. C (um) i[SV:1] don't know.
C i[SV:1] don't need my help. C (i) i[SV:1] wanna play with baby.
C (i) i[SV:1] wanna play that.
C i[SV:1] want that. [×7]
C i[SV:1] need this.
C i[SV:1] wanna (try) try cut.
C (uh) i[SV:1] want open the door.
C i[SV:1] want a other baby out.
C (i*) i[SV:1] wanna try. [×2]
C i[SV:1] want juice.
C i[SV:1] want eat. [×2]
C i[SV:1] wanna try that stuff.
C i[SV:1] wash my hand.
C i[SV:1] wanna make a egg.
C i[SV:1] cut. [×2]
C i[SV:1] cut it that.
C i[SV:1] eat now.
SV:2 C and you[SV:2] get the elephant one. C you[SV:2] eat the pizza. C you[SV:2] eat broccoli, ma?
C and you[SV:2] got to blow it.
C you[SV:2] have this one.
C you[SV:2] don't want it?
C <you[SV:2] gotta> use your little finger/s.
SV:3 C (um) something else[SV:3] go. C I wanna try chicken[SV:3] go/ing in. C and chicken[SV:3] make.
C and the farmer[SV:3] can feed the sheep/s. C and that[SV:3]/'s go top. C pizza[SV:3] come/ing, ma.
C he[SV:3] want this apple. C pizza[SV:3] come/ing.
C (ch*) it[SV:3]/'has got cheese. C a knife[SV:3] stir.
C somebody[SV:3]/'s come/ing.
C he[SV:3] got soap.
C he[SV:3] can take a walk.
SV:1P C we[SV:1P] can build a tower now.
C we[SV:1P] gotta buckle him up.
C we[SV:1P] got soap in there.
SV:3P C those[SV:3P] look a bit orangish. C they[SV:3P] eat some more pizza.
C those[SV:3P] look like pumpkin/s.
×
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