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A Cross-Sectional Analysis of Developmental Trajectories of Vocabulary Comprehension among Children and Adolescents with Down Syndrome or Intellectual Disability of Undifferentiated Aetiology

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Title: A Cross-Sectional Analysis of Developmental Trajectories of Vocabulary Comprehension among Children and Adolescents with Down Syndrome or Intellectual Disability of Undifferentiated Aetiology
Language: English
Authors: Facon, Bruno, Courbois, Yannick, Magis, David
Source: Journal of Intellectual & Developmental Disability. 2016 41(2):140-149.
Availability: Taylor & Francis. Available from: Taylor & Francis, Ltd. 530 Walnut Street Suite 850, Philadelphia, PA 19106. Tel: 800-354-1420; Tel: 215-625-8900; Fax: 215-207-0050; Web site: http://www.tandf.co.uk/journals
Peer Reviewed: Y
Page Count: 10
Publication Date: 2016
Document Type: Journal Articles
Reports - Research
Education Level: Kindergarten
Descriptors: Vocabulary Development, Comprehension, Children, Adolescents, Down Syndrome, Intellectual Disability, Cognitive Ability, Clinical Diagnosis, Correlation, Intelligence Tests, Verbal Ability, Vocabulary, Kindergarten, Special Schools
Assessment and Survey Identifiers: Peabody Picture Vocabulary Test, Boehm Test of Basic Concepts, Raven Progressive Matrices
DOI: 10.3109/13668250.2016.1160370
ISSN: 1469-9532
Abstract: Background: In this work we sought to expand our knowledge of developmental trajectories of subcomponents of the language systems of individuals with intellectual disability (ID). We aimed to explore how "general" and "relational" vocabularies evolve as a function of cognitive level. Method: Developmental trajectories of general and relational vocabulary comprehension were compared among typically developing (TD) children and children and adolescents with ID of undifferentiated aetiology (UND) or Down syndrome (DS). Results: Comparisons between TD participants and participants with UND showed no interaction between cognitive level and diagnostic status for general vocabulary, and only a very weak interaction for relational vocabulary. Comparisons between TD participants and participants with DS failed to reveal group-specific trajectories. Performance in general vocabulary was higher than in relational vocabulary for participants with UND and DS. Conclusion: The developmental trajectories of vocabulary appear to be globally comparable for participants with or without ID.
Abstractor: As Provided
Number of References: 41
Entry Date: 2018
Accession Number: EJ1188815
Database: ERIC
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  Value: <anid>AN0114435074;ddi01jun.16;2019Feb20.13:13;v2.2.500</anid> <title id="AN0114435074-1">A cross-sectional analysis of developmental trajectories of vocabulary comprehension among children and adolescents with Down syndrome or intellectual disability of undifferentiated aetiology. </title> <p>Background In this work we sought to expand our knowledge of developmental trajectories of subcomponents of the language systems of individuals with intellectual disability (ID). We aimed to explore how general and relational vocabularies evolve as a function of cognitive level. Method Developmental trajectories of general and relational vocabulary comprehension were compared among typically developing (TD) children and children and adolescents with ID of undifferentiated aetiology (UND) or Down syndrome (DS). Results Comparisons between TD participants and participants with UND showed no interaction between cognitive level and diagnostic status for general vocabulary, and only a very weak interaction for relational vocabulary. Comparisons between TD participants and participants with DS failed to reveal group-specific trajectories. Performance in general vocabulary was higher than in relational vocabulary for participants with UND and DS. Conclusion The developmental trajectories of vocabulary appear to be globally comparable for participants with or without ID.</p> <p>Keywords: intellectual disability; Down syndrome; language; lexical development; developmental trajectory</p> <hd id="AN0114435074-2">Introduction</hd> <p>A growing number of studies suggest that, in the cases of fragile X (FXS), Williams syndrome (WS), and Down syndrome (DS; Hodapp & Dykens, [<reflink idref="bib26" id="ref1">26</reflink>]), for example, aetiology can shape the behavioural and cognitive profiles of people with intellectual disability (ID). These cognitive, behavioural, or emotional features constitute a "signature" that allows each syndrome to be distinguished from the others to some extent (Cornish, Bertone, Kogan, & Scerif, [<reflink idref="bib10" id="ref2">10</reflink>]). However, despite their importance in terms of diagnosis, prognosis, or educational intervention, the concepts of phenotype and endophenotype still too often have a static connotation, as if the particular characteristics of each syndrome were stable over time and, thus, would necessarily be observed at any and all points of development. This "end-of-state," "snapshot," "static," or "fixist" view of syndrome profiling (Karmiloff-Smith, [<reflink idref="bib29" id="ref3">29</reflink>]) is seriously challenged by the trajectory approach to developmental disorders, whose two main principles are that (a) syndrome (endo)phenotypes evolve in the course of development, and (b) no convincing explanation for a given (endo)phenotype can be provided without tracing the developmental course of each of its components (Knowland & Thomas, [<reflink idref="bib31" id="ref4">31</reflink>]).</p> <p>The evolving nature of cognitive endophenotypes is suggested by a growing number of studies. The gap between sequential and simultaneous processing of information increases with age in children with FXS (Hodapp, Dykens, Ort, Zelinsky, & Leckman, [<reflink idref="bib27" id="ref5">27</reflink>]). Likewise, fundamental components of attention (specifically, selective and sustained attention, inhibitory control) also evolve differently with chronological age (CA) and mental age (MA) among typically developing (TD) children, and children with FXS and DS (Cornish, Scerif, & Karmiloff-Smith, [<reflink idref="bib11" id="ref6">11</reflink>]), indicating specific developmental trends for these cognitive processes across these groups. There has also been seen, in the area of language acquisition, a developmental discrepancy between syntactic and lexical abilities of children and adolescents with DS (Chapman & Kay-Raining Bird, [<reflink idref="bib7" id="ref7">7</reflink>]). Similarly, cross-sectional and longitudinal data indicate that the discrepancy between vocabulary and nonverbal cognitive level among individuals with WS does not remain constant over time. Instead, the discrepancy increases with CA and MA, thus suggesting different rates of development for these two types of abilities and, consequently, a <emph>progressive</emph> emergence of this well-known specificity of individuals with WS (Brock, Jarrold, Farran, Laws, & Riby, [<reflink idref="bib5" id="ref8">5</reflink>]).</p> <p>The purpose of the present work was to expand our knowledge of developmental trajectories of subcomponents of the language system among individuals with ID. We aimed to explore how receptive lexical knowledge evolves as a function of cognitive development. For further refinements in the analyses, a distinction is made between <emph>general</emph> and <emph>relational</emph> vocabulary. General vocabulary mainly comprises concrete or abstract nouns, verbs, and adjectives referring to objects, actions, events, states, or processes. The most well-known receptive measure of this kind of vocabulary is the Peabody Picture Vocabulary Test (PPVT; Dunn & Dunn, [<reflink idref="bib13" id="ref9">13</reflink>]).[<reflink idref="bib1" id="ref10">1</reflink>] Relational vocabulary is of a narrower nature, consisting exclusively of abstract words indicating <emph>relationships</emph> between objects, persons, or events. Among other psychometric tests, the Boehm Test of Basic Concepts (Boehm, [<reflink idref="bib2" id="ref11">2</reflink>], [<reflink idref="bib3" id="ref12">3</reflink>]) is intended to evaluate relational vocabulary.</p> <p>General and relational vocabulary do not correlate to the same degree with cognitive developmental age among individuals with ID. The Boehm test scores of children with ID are far better correlated with nonverbal MA than are PPVT scores. Conversely, the PPVT is better correlated with CA than is the Boehm (Fazio, Johnston, & Brandl, [<reflink idref="bib22" id="ref13">22</reflink>]). In addition, performance on general receptive vocabulary tests keeps pace with or even exceeds nonverbal cognitive measures for individuals with WS (Brock et al., [<reflink idref="bib5" id="ref14">5</reflink>]; Mervis & John, [<reflink idref="bib34" id="ref15">34</reflink>]), DS (Chapman, [<reflink idref="bib6" id="ref16">6</reflink>]; Glenn & Cunningham, [<reflink idref="bib24" id="ref17">24</reflink>]; Laws & Bishop, [<reflink idref="bib32" id="ref18">32</reflink>]; Miolo, Chapman, & Sindberg, [<reflink idref="bib35" id="ref19">35</reflink>]), or those of undifferentiated aetiology (UND; Facon, Bollengier, & Grubar, [<reflink idref="bib15" id="ref20">15</reflink>]), particularly in late childhood and adolescence (Facon, Facon-Bollengier, & Grubar, [<reflink idref="bib16" id="ref21">16</reflink>]; Facon, Grubar, & Gardez, [<reflink idref="bib17" id="ref22">17</reflink>]). By contrast, measures of relational vocabulary appear either commensurate with (Facon, Magis, & Courbois, [<reflink idref="bib18" id="ref23">18</reflink>]; Miolo et al., [<reflink idref="bib35" id="ref24">35</reflink>]) or below those expected on the basis of intellectual abilities (Mervis & John, [<reflink idref="bib34" id="ref25">34</reflink>]; Price, Roberts, Vandergrift, & Martin, [<reflink idref="bib36" id="ref26">36</reflink>]; Stojanovik, Perkins, & Howard, [<reflink idref="bib40" id="ref27">40</reflink>]). Thus, the "lexical profile" of individuals with ID arising from this set of studies appears to be <emph>relational vocabulary ≤ cognitive level ≤ general vocabulary</emph>.</p> <p>Many of the studies conducted on the lexical development of children with ID feature a single age-point matching methodology. From a developmental viewpoint, they thus have a decidedly static character. Furthermore, they are rarely concerned with both general and relational vocabularies. Consequently, we do not know whether the abovementioned lexical profile holds regardless of the cognitive level of the participants or perhaps changes over the course of cognitive development. In the present work we addressed this issue using a cross-sectional developmental approach in two studies.</p> <p>In the first study, tests of general vocabulary and relational vocabulary were administered to a large group of participants with UND who were matched with a group of TD children on a measure of nonverbal cognitive development. By optimising the power of the statistical analyses, the large samples permitted detection of even subtle between-group differences of slope with regard to the relationship between cognitive level and general or relational lexical knowledge.</p> <p>The second study was conducted similarly, but with participants with DS rather than participants with UND. Given this homogenisation of aetiology, the sample sizes were necessarily smaller, thus reducing statistical power. However, by allowing an examination of whether participants with DS per se have specific lexical-development trajectories, this second study was more in line with the syndrome-based approach to understanding ID (Hodapp & Dykens, [<reflink idref="bib26" id="ref28">26</reflink>]). Moreover, it yielded more detailed information on developmental trajectory of both relational and general vocabularies of people with DS, of which there is almost no extant literature. The French National Research Agency supported this work, the Ethics Committee of the Unit for Research in Cognitive and Affective Sciences (University of Lille) granted ethical approval, and written informed consent was obtained from participants' parents.</p> <hd id="AN0114435074-3">Study 1</hd> <p></p> <hd id="AN0114435074-4">Method</hd> <p></p> <hd id="AN0114435074-5">Instruments</hd> <p>The Echelle de Vocabulaire en Images Peabody (EVIP, Form B; Dunn, Thériault-Whalen, & Dunn, [<reflink idref="bib14" id="ref29">14</reflink>] – the French version of the PPVT) and the Test des Concepts de Base (BOEHM; Boehm, [<reflink idref="bib2" id="ref30">2</reflink>], [<reflink idref="bib3" id="ref31">3</reflink>] – the French version of the Boehm Test of Basic Concepts) were individually administered with no time limits by Master's students in developmental psychology or contract psychologists trained in psychometrics. Testing sessions were conducted in quiet rooms situated near participants' classrooms.</p> <p>For each item of the EVIP, four pictures are presented on a single page and the participant must select the one corresponding to a word spoken by the examiner. The test covers the age range 2½ to 18 years. It comprises 170 items belonging to different categories, such as nouns, verbs, or adjectives (e.g., <emph>padlock</emph>, <emph>share</emph>, <emph>furious</emph>), root and inflected words (e.g., <emph>mason</emph>, <emph>fragment</emph> vs. <emph>cluttered</emph>, <emph>lubricated</emph>), concrete versus verbally defined words (<emph>shrub</emph>, <emph>river</emph> vs. <emph>complaint</emph>, <emph>nutritive</emph>), or basic, superordinate, and subordinate nouns (e.g., <emph>car</emph> vs. <emph>vehicle</emph> vs. <emph>ambulance</emph>). The median internal consistency coefficient for the standardisation sample was 0.81 for Form A and 0.80 for Form B (Dunn et al., [<reflink idref="bib14" id="ref32">14</reflink>]). A recent study conducted with participants with UND and participants with DS yielded internal consistency ranging from 0.84 to 0.89. It also showed that the rank order of item difficulty was remarkably similar for participants with and without ID (Facon, Nuchadee, & Bollengier, [<reflink idref="bib21" id="ref33">21</reflink>]).</p> <p>For each item of the BOEHM, four to six items are displayed on a page and the participant must select the one corresponding to a concept spoken by the examiner. This test evaluates only abstract words, and these indicate spatial, temporal, dimensional, quantitative, or class relationships between objects, persons, or events, such as <emph>behind, third, inside, larger, before, in front of</emph>, or <emph>never</emph>. The BOEHM comprises two French-language versions, one for preschool (Boehm, [<reflink idref="bib2" id="ref34">2</reflink>]) and the other for kindergarten to 2nd grade (Boehm, [<reflink idref="bib3" id="ref35">3</reflink>]). The Preschool version, intended for children aged 3 to 5 years 11 months, comprises 76 items designed to evaluate 38 concepts (two items per concept). The Kindergarten to 2nd grade version applies to children aged 5 to 8 years. It comprises 50 items each evaluating a particular concept. For the study, the two versions of Boehm's test were combined into a single test that was individually administered to each participant. This was done to avoid the inevitable floor and ceiling effects that would occur using only one or the other test. To reduce test duration, one item from each conceptual pair of the Kindergarten version was deleted, as was one from each pair of items that were duplicated across the two versions. The final test comprised 72 items administered according to the order recommended in the original test manuals. This modified version of the test was used in a recent study conducted with participants with and without ID. In this study reliability coefficients approached 0.90, and the rank order difficulty of items was very similar across the two types of participants (Facon, Magis, & Courbois, [<reflink idref="bib18" id="ref36">18</reflink>]).</p> <p>Altogether these data indicate that the EVIP and the BOEHM can be used with confidence to evaluate the vocabulary of people with ID. Moreover, the fact that both are tests of receptive vocabulary and require the same response modality will greatly facilitate the interpretation of potential between-groups differences in developmental trajectories.</p> <p>Raven's Coloured Progressive Matrices (RAVEN; Raven, Court, & Raven, [<reflink idref="bib37" id="ref37">37</reflink>]) was also administered to all participants to obtain an estimate of their nonverbal cognitive level. The RAVEN was chosen because of the simplicity and speed of its administration and scoring, its reliability, and the great similarity of item response profiles to which it gives rise for participants with and without ID (Facon, Magis, Nuchadee, & De Boeck, [<reflink idref="bib19" id="ref38">19</reflink>]; Facon & Nuchadee, [<reflink idref="bib20" id="ref39">20</reflink>]). Moreover, the RAVEN is used extensively to assess the fluid-like component of intelligence of typical and clinical populations of children (Cotton et al., [<reflink idref="bib12" id="ref40">12</reflink>]). The RAVEN was selected over measures of crystallised intelligence because the crystallised component of human cognition is almost always appraised by means of verbal measures that are highly correlated with vocabulary scores (Schneider & McGrew, [<reflink idref="bib38" id="ref41">38</reflink>]). Thus, the use of such a measure would have induced a strong overlap between the dependent variables and the variable used to control the cognitive level of participants.</p> <p>RAVEN raw scores can be converted to percentiles but not to MAs. However, given the fact that, by construction, intellectual development scale raw scores are highly correlated with MAs or other developmental indices, the raw score of each participant on the RAVEN was considered as a <emph>relative</emph> measure of his or her nonverbal cognitive level. Moreover, to meet the need for homogenisation, the statistical analyses of the BOEHM and the EVIP also focused on the raw scores. The fact that the two versions of Boehm's test were combined into a single test also precluded the use of normative indices.</p> <hd id="AN0114435074-6">Participants</hd> <p>The tests were administered to TD participants recruited from regular kindergarten classes and participants with UND enrolled in special education schools for children and adolescents with mild to severe ID. The group of participants with UND comprised mostly people with either no aetiologic diagnosis or only a hypothetical one. It also comprised participants with ID of highly varied known origins (genetic syndromes such as WS or FXS, foetal alcohol syndrome, congenital, perinatal or neonatal brain injuries, infectious diseases, etc.) making irrelevant the constitution of specific aetiological groups. Given the fact that our second study was conducted with participants with DS, none of the participants with this syndrome was included in the group with UND.</p> <p>Participants with UND were exactly matched with TD participants using their RAVEN raw scores. The aim of this matching was to make the distribution of nonverbal cognitive levels exactly the same regardless of diagnostic status. Then, if differences in trajectories are observed between TD participants and participants with UND for the EVIP or the BOEHM, the shape of the distributions of RAVEN could not be invoked as a potentially confounding factor.</p> <p>There were 286 TD participants (<emph>M</emph><subs>CA</subs> = 4.71 years, <emph>SD</emph> = 0.64 years, 139 females, 147 males) and 286 participants with UND (<emph>M</emph><subs>CA</subs> = 12.79 years, <emph>SD</emph> = 3.00 years, 128 females, 158 males). Descriptive statistics for the RAVEN, the EVIP, and the BOEHM are given in Table 1. Because of the matching procedure, the difference between RAVEN mean scores of TD participants and participants with UND is nonsignificant (<emph>t<subs>2-tailed</subs></emph> = 0.000, <emph>df</emph> = 570, <emph>p</emph> = 1.00), as is the Levene test for homogeneity of variance (<emph>F</emph><subs>(<reflink idref="bib1" id="ref42">1</reflink>,<reflink idref="bib570" id="ref43">570</reflink>)</subs> = 0.000, <emph>p</emph> = 1.00). Cronbach's α coefficients are also given in Table 1. They are so similar for TD participants and participants with UND that no potential between-group developmental trajectory differences could be attributed to differential reliability of the tests used to measure the latent traits. Moreover, in spite of the use of a modified version of the BOEHM test, Cronbach's α was highly satisfactory for both groups.</p> <p>Table 1. Descriptive statistics and Cronbach's alpha coefficients for raw scores on the RAVEN, the EVIP, and the BOEHM.</p> <p> <ephtml> <table><thead valign="bottom"><tr><td /><td>RAVEN</td><td>EVIP</td><td>BOEHM</td></tr><tr><td /><td>TD</td><td>UND</td><td>TD</td><td>UND</td><td>TD</td><td>UND</td></tr></thead><tbody><tr><td><italic>M</italic></td><td>16.06</td><td>16.06</td><td>65.38</td><td>75.07</td><td>51.88</td><td>52.43</td></tr><tr><td><italic>SD</italic></td><td>4.31</td><td>4.31</td><td>14.18</td><td>15.45</td><td>10.50</td><td>13.06</td></tr><tr><td>Skewness</td><td>0.319</td><td>0.319</td><td>0.134</td><td>−0.144</td><td>−0.356</td><td>−0.701</td></tr><tr><td>Kurtosis</td><td>0.093</td><td>0.093</td><td>−0.703</td><td>−0.226</td><td>−0.369</td><td>−0.452</td></tr><tr><td>Cronbach's <italic>α</italic></td><td>0.700</td><td>0.698</td><td>0.873</td><td>0.899</td><td>0.913</td><td>0.942</td></tr></tbody></table> </ephtml> </p> <p> <emph>Note</emph>. <emph>n</emph> = 286 for each group, TD and UND. The standard errors for skewness and kurtosis are 0.144 and 0.287, respectively. RAVEN = Raven Coloured Progressive Matrices; EVIP = Echelle de Vocabulaire en Images Peabody; BOEHM = Test des Concepts de Base; TD = typically developing participants; UND = participants with intellectual disability of undifferentiated aetiology.</p> <hd id="AN0114435074-7">Statistical analyses</hd> <p>Separate multiple regression analyses were performed on the EVIP and the BOEHM scores to estimate the contributions of the RAVEN, the diagnostic status and the RAVEN × status interaction. The RAVEN was entered first in the regression equation. The status variable, coded respectively 0 and 1 for TD participants and participants with UND, was then entered followed by the interaction term (RAVEN × status). If an overall effect of diagnostic status was observed, it would be represented by a difference in the intercepts indicating a delayed onset for the TD group or the group with UND. On the other hand, if the interaction were significant, it would indicate a between-groups difference in slopes and, thus, a difference in rates of vocabulary development as a function of cognitive development.</p> <p>To check the linearity of the relationship between the RAVEN and the EVIP and between the RAVEN and the BOEHM scores, <emph>R<sups>2</sups></emph>s obtained using linear, quadratic, and cubic equations were compared (Cohen, Cohen, West, & Aiken, [<reflink idref="bib9" id="ref44">9</reflink>]). Results of these comparisons showed that the quadratic term did significantly increase the variance explained by the linear term, but only for the BOEHM, a phenomenon that could be anticipated given the skewness of distributions observed for this test for which a ceiling effect is particularly evident (see Table 1), especially for the participants with UND (z<emph><subs>skew</subs></emph> = 4.865, <emph>p</emph> < .00001). For the EVIP, Δ<emph>R<sups>2</sups></emph><subs>linear vs. quadratic</subs> = 0.001, <emph>F</emph><subs>(<reflink idref="bib1" id="ref45">1</reflink>,<reflink idref="bib569" id="ref46">569</reflink>)</subs> = 0.587, <emph>p</emph> = .444, and Δ<emph>R<sups>2</sups></emph><subs>linear + quadratic vs. cubic</subs> = 0.000, <emph>F</emph><subs>(<reflink idref="bib1" id="ref47">1</reflink>,<reflink idref="bib568" id="ref48">568</reflink>)</subs> = 0.179, <emph>p</emph> = .673. For the BOEHM, Δ<emph>R<sups>2</sups></emph><subs>linear vs. quadratic </subs>= 0.022, <emph>F</emph><subs>(<reflink idref="bib1" id="ref49">1</reflink>,<reflink idref="bib569" id="ref50">569</reflink>)</subs> = 21.231, <emph>p</emph> = .0000, and Δ<emph>R<sups>2</sups></emph><subs>linear + quadratic vs. cubic</subs> = 0.000, <emph>F</emph><subs>(<reflink idref="bib1" id="ref51">1</reflink>,<reflink idref="bib568" id="ref52">568</reflink>)</subs> = 0.024, <emph>p</emph> = .876. Therefore, the RAVEN raw scores were log transformed to straighten their relationship with the BOEHM so that statistical analyses could be conducted within a linear framework. By the same token, no transformation was made for the analyses involving the EVIP because of its naturally linear relationship with the RAVEN in each group. Finally, to facilitate the interpretation of results, the EVIP, BOEHM, and RAVEN scores were standardised to <emph>z</emph> scores based on the grand mean and standard deviation for the entire sample of 572 participants.</p> <hd id="AN0114435074-8">Results</hd> <p>The main results of the regression analyses of EVIP and BOEHM <emph>z</emph> scores are presented in Table 2 and the corresponding bivariate plots in Figure 1. These indicate that the RAVEN is strongly related to both general and relational vocabulary. However, the relationship appears stronger for the BOEHM than for the EVIP. Indeed, the respective adjusted coefficients of determination (<emph>R<sups>2</sups></emph> adj.) were 0.402 and 0.287, and the regression coefficients (<emph>b</emph> = 0.635 and <emph>b</emph> = 0.536) were significantly different from one another (<emph>t</emph> = 2.051, <emph>df</emph> = 568, <emph>p</emph> = .041). Moreover, although diagnostic status had no effect on the BOEHM score (<emph>b</emph> = 0.047, partial <emph>F</emph><subs>(<reflink idref="bib1" id="ref53">1</reflink>,<reflink idref="bib569" id="ref54">569</reflink>)</subs> = 0.520, <emph>p</emph> = .471), its influence on the EVIP was statistically significant (<emph>b</emph> = 0.622, partial <emph>F</emph><subs>(<reflink idref="bib1" id="ref55">1</reflink>,<reflink idref="bib569" id="ref56">569</reflink>)</subs> = 89.48, <emph>p</emph> < .001). Thus, the difference between TD participants and participants with UND was only <emph>SD</emph> = 0.047 for the BOEHM but <emph>SD</emph> = 0.622 in favour of participants with UND for the EVIP, which corresponds to a moderate effect size (Cohen, [<reflink idref="bib8" id="ref57">8</reflink>]). Finally, the RAVEN × diagnostic status interaction was significant only for the BOEHM. However, the effect was small because the increment of the adjusted <emph>R<sups>2</sups></emph> yielded by introduction of the multiplicative term was only 0.012; that is, an additional 1.2% of explained variance in BOEHM <emph>z</emph> scores.</p> <p>Graph: Figure 1. EVIP (top panel) and BOEHM (bottom panel) z scores as a function of RAVEN z score for TD participants (n = 286) and participants with UND (n = 286). RAVEN = Raven Coloured Progressive Matrices; EVIP = Echelle de Vocabulaire en Images Peabody; BOEHM = Test des Concepts de Base; TD = typically developing participants; UND = participants with intellectual disability of undifferentiated aetiology.</p> <p>Table 2. Multiple regression analyses of EVIP and BOEHM z scores of TD and UND participants.</p> <p> <ephtml> <table><thead valign="bottom"><tr><td>Variables in equation</td><td /><td>EVIP <italic>z</italic> score</td></tr><tr><td><italic>R<sup>2</sup></italic> adj.</td><td>Overall <italic>F</italic></td><td><italic>p</italic></td><td><italic>b</italic></td><td>Partial <italic>F</italic></td><td><italic>p</italic></td></tr></thead><tbody><tr><td><bold>Step 1</bold></td><td>RAVEN</td><td>.287</td><td>230.326</td><td>.001</td><td>0.536</td><td>230.326</td><td>.001</td></tr><tr><td><bold>Step 2</bold></td><td>RAVEN</td><td>.382</td><td>177.779</td><td>.001</td><td>0.536</td><td>266.079</td><td>.001</td></tr><tr><td /><td>Status</td><td /><td /><td /><td>0.622</td><td>89.480</td><td>.001</td></tr><tr><td><bold>Step 3</bold></td><td>RAVEN</td><td>.382</td><td>118.578</td><td>.001</td><td>0.513</td><td>121.718</td><td>.001</td></tr><tr><td /><td>Status</td><td /><td /><td /><td>0.622</td><td>89.400</td><td>.001</td></tr><tr><td /><td>RAVEN × Status</td><td /><td /><td /><td>0.033</td><td>0.493</td><td>.483</td></tr><tr><td /><td /><td>BOEHM <italic>z</italic> score</td></tr><tr><td>Variables in equation</td><td><italic>R<sup>2</sup></italic> adj.</td><td>Overall <italic>F</italic></td><td><italic>p</italic></td><td><italic>b</italic></td><td>Partial <italic>F</italic></td><td><italic>p</italic></td></tr><tr><td><bold>Step 1</bold></td><td>RAVEN</td><td>.402</td><td>384.672</td><td>.001</td><td>0.635</td><td>384.672</td><td>.001</td></tr><tr><td><bold>Step 2</bold></td><td>RAVEN</td><td>.401</td><td>192.434</td><td>.001</td><td>0.635</td><td>384.347</td><td>.001</td></tr><tr><td /><td>Status</td><td /><td /><td /><td>0.047</td><td>0.520</td><td>.471</td></tr><tr><td><bold>Step 3</bold></td><td>RAVEN</td><td>.413</td><td>135.009</td><td>.001</td><td>0.522</td><td>132.441</td><td>.001</td></tr><tr><td /><td>Status</td><td /><td /><td /><td>0.047</td><td>0.530</td><td>.467</td></tr><tr><td /><td>RAVEN × Status</td><td /><td /><td /><td>0.160</td><td>12.429</td><td>.001</td></tr></tbody></table> </ephtml> </p> <p> <emph>Note. N</emph> = 572. <emph>R</emph><sups>2</sups> adj. = adjusted squared multiple correlation coefficient; <emph>b</emph> = unstandardised regression coefficient; RAVEN = Raven Coloured Progressive Matrices <emph>z</emph> score; Status = respectively 0 and 1 for TD participants and participants with UND; EVIP = Echelle de Vocabulaire en Images Peabody; BOEHM = Test des Concepts de Base; TD = typically developing participants; UND = participants with intellectual disability of undifferentiated aetiology.</p> <p>Statistical analyses were also conducted to examine the influence of gender on the developmental trajectories of the two types of vocabularies. These analyses showed, for TD participants as well as for participants with UND, that neither the effect of gender nor the RAVEN × gender interaction was statistically significant.</p> <hd id="AN0114435074-9">Study 2</hd> <p></p> <hd id="AN0114435074-10">Method</hd> <p></p> <hd id="AN0114435074-11">Instruments and participants</hd> <p>The tests used for Study 2 were the same as those used in Study 1. There were two groups of 45 participants each, exactly matched using their RAVEN raw scores. The first group included TD children (<emph>M</emph><subs>CA</subs> = 4.34 years, <emph>SD</emph> = 0.61 years, 22 females, 23 males) from regular kindergartens. The second group were participants with DS (<emph>M</emph><subs>CA</subs> = 15.31 years, <emph>SD</emph> = 3.27 years, 26 females, 19 males).</p> <p>For these two groups, descriptive statistics for the RAVEN, the BOEHM, and the EVIP are presented in Table 3. Because of the matching procedure, the difference between the groups' RAVEN means is exactly zero (<emph>t<subs>2-tailed</subs></emph> = 0.000, <emph>df</emph> = 88, <emph>p</emph> = 1.00), as is the Levene test for homogeneity of variances, <emph>F</emph><subs>(<reflink idref="bib1" id="ref58">1</reflink>,<reflink idref="bib88" id="ref59">88</reflink>)</subs> = 0.000, <emph>p</emph> = 1.00.</p> <p>Table 3. Descriptive statistics for raw scores on the RAVEN, the EVIP, and the BOEHM.</p> <p> <ephtml> <table><thead valign="bottom"><tr><td /><td>RAVEN</td><td>EVIP</td><td>BOEHM</td></tr><tr><td /><td>TD</td><td>DS</td><td>TD</td><td>DS</td><td>TD</td><td>DS</td></tr></thead><tbody><tr><td><italic>M</italic></td><td>13.56</td><td>13.56</td><td>57.40</td><td>60.73</td><td>44.49</td><td>41.49</td></tr><tr><td><italic>SD</italic></td><td>4.05</td><td>4.05</td><td>12.23</td><td>11.99</td><td>11.48</td><td>9.96</td></tr><tr><td>Skewness</td><td>0.259</td><td>0.259</td><td>0.208</td><td>−0.794</td><td>0.025</td><td>0.159</td></tr><tr><td>Kurtosis</td><td>−0.142</td><td>−0.142</td><td>−0.426</td><td>0.937</td><td>−0.981</td><td>−0.265</td></tr></tbody></table> </ephtml> </p> <p> <emph>Note</emph>. <emph>n</emph> = 45 for each group, TD and DS. The standard errors for skewness and kurtosis are 0.354 and 0.695, respectively. RAVEN = Raven Coloured Progressive Matrices; EVIP = Echelle de Vocabulaire en Images Peabody; BOEHM = Test des Concepts de Base; TD = typically developing participants; DS = participants with Down syndrome.</p> <hd id="AN0114435074-12">Statistical analyses</hd> <p>In contrast with Study 1, the relationship between the RAVEN and the EVIP and between the RAVEN and the BOEHM scores appeared linear. Indeed, all variations of <emph>F</emph> resulting from the introduction of squared and cubic terms in the regression equation were nonsignificant. Therefore, statistical analyses were conducted without transforming the RAVEN scores. The lower cognitive level of participants of this second study probably explains this fact. Indeed, the lower the level of groups on the matching variable, the lower the risk that participants will reach the maximum score on the dependant variable.</p> <hd id="AN0114435074-13">Results</hd> <p>Bivariate plots of EVIP and BOEHM <emph>z</emph> scores for Study 2 are provided in Figure 2. There is a strong relationship between the RAVEN and performance on the two vocabulary tests, but, contrary to Study 1, the strength of the relationship is not significantly greater for the BOEHM than for the EVIP (<emph>b</emph><subs>BOEHM</subs> = 0.625, <emph>b</emph><subs>EVIP</subs> = 0.556, <emph>t</emph> = 0.568, <emph>df</emph> = 86, <emph>p</emph> = .572). However, the failure to reach statistical significance probably resulted from the study's low power. Indeed, the difference between the regression coefficients and between the adjusted <emph>R<sups>2</sups></emph> (0.384 vs. 0.301) are not substantially different from those found to be significant in Study 1 and are in the same direction.</p> <p>Graph: Figure 2. EVIP (left panel) and BOEHM (right panel) z scores as a function of Raven z score for TD participants (n = 45) and participants with DS (n = 45). RAVEN = Raven Coloured Progressive Matrices; EVIP = Echelle de Vocabulaire en Images Peabody; BOEHM = Test des Concepts de Base; TD = typically developing participants; DS = participants with Down syndrome.</p> <p>The effect of diagnostic status only approached significance, but the two tests' slopes had opposite signs (<emph>b</emph><subs>EVIP</subs> = 0.274, partial <emph>F</emph><subs>(<reflink idref="bib1" id="ref60">1</reflink>,<reflink idref="bib87" id="ref61">87</reflink>)</subs> = 2.461, <emph>p</emph> = .120, <emph>b</emph><subs>BOEHM</subs> = −0.278, partial <emph>F</emph><subs>(<reflink idref="bib1" id="ref62">1</reflink>,<reflink idref="bib87" id="ref63">87</reflink>)</subs> = 2.88, <emph>p</emph> = .093). This means that, compared to TD children, participants with DS tend to have higher scores on the EVIP but lower scores on the BOEHM. The effect of the multiplicative terms was not significant for either test. Thus, one may conclude that the trajectories of development of general and relational vocabulary are not different for the two groups of participants, even if, for the BOEHM, the slope seems steeper for TD participants than for participants with DS.</p> <p>Analysis of the residuals revealed an EVIP outlier. Consequently, given the small sample sizes, the analysis was rerun while excluding this observation. No notable change in the model parameters was observed in this secondary analysis, except for an increase in the diagnostic status regression coefficient and, therefore, a decrease in its <emph>p</emph> value, which reached significance (<emph>b</emph> = 0.350, partial <emph>F</emph><subs>(<reflink idref="bib1" id="ref64">1</reflink>,<reflink idref="bib86" id="ref65">86</reflink>)</subs> = 4.095, <emph>p</emph> = .046). Notwithstanding this result, it must be noted that the effect size was smaller than that observed in Study 1. Indeed, the mean performance of participants with DS on the EVIP was 0.35 <emph>SD</emph> higher than that of TD participants, whereas the difference between participants with UND and TD participants in Study 1 was <emph>SD</emph> = 0.62.</p> <p>To complete the analysis, a sample of participants with UND from Study 1 were exactly matched with participants with DS on the basis of their RAVEN scores while ensuring that the means and standard deviations of the two groups were also similar for CA. Given this matching procedure, no significant differences between the two groups were found for the means or the variances (<emph>t<subs>2-tailed</subs></emph> = 0.000, <emph>df</emph> = 88, <emph>p</emph> = 1.00 and <emph>F</emph><subs>(<reflink idref="bib1" id="ref66">1</reflink>,<reflink idref="bib88" id="ref67">88</reflink>)</subs> = 0.000, <emph>p</emph> = 1.00 for the RAVEN; <emph>t<subs>2-tailed</subs></emph> = −0.173, <emph>df</emph> = 88, <emph>p</emph> = .863 and <emph>F</emph><subs>(<reflink idref="bib1" id="ref68">1</reflink>,<reflink idref="bib88" id="ref69">88</reflink>)</subs> = 0.062, <emph>p</emph> = .804 for CA). After checking the condition of linearity of relationships between the RAVEN and each of the two other tests, multiple regression analyses were performed on the EVIP and the BOEHM scores to estimate the contributions of the RAVEN, diagnostic status (UND = 0, DS = 1), and the RAVEN × status interaction. For the EVIP there was a significant effect of RAVEN (Δ<emph>R<sups>2</sups></emph> adj. = 0.296, <emph>p</emph> < .001) and diagnostic status (Δ<emph>R<sups>2</sups></emph> adj. = 0.166, <emph>p</emph> < .001). However, the contribution of the multiplicative term to the variance was only marginally significant (Δ<emph>R<sups>2</sups></emph> adj. = 0.013, <emph>p</emph> = .074). For the BOEHM, the three variables introduced in the regression equation significantly increased the explained variance (Δ<emph>R<sups>2</sups></emph> adj. = 0.370, <emph>p</emph> < .001 for the RAVEN; Δ<emph>R<sups>2</sups></emph> adj. = 0.043, <emph>p</emph> = .008 for status; and Δ<emph>R<sups>2</sups></emph> adj. = 0.032, <emph>p</emph> = .017 for RAVEN × diagnostic status). Bivariate plots and regression lines observed for the two groups and the two tests are shown in Figure 3.</p> <p>Graph: Figure 3. EVIP (left panel) and BOEHM (right panel) z scores as a function of Raven z score for participants with UND (n = 45) and participants with DS (n = 45). RAVEN = Raven Coloured Progressive Matrices; EVIP = Echelle de Vocabulaire en Images Peabody; BOEHM = Test des Concepts de Base; UND = participants with intellectual disability of undifferentiated aetiology; DS = participants with Down syndrome.</p> <hd id="AN0114435074-14">Discussion</hd> <p>A strong consensus has emerged over the last decade in the intellectual disability literature as to the importance of studying trajectories of behavioural, cognitive, or linguistic aspects of development using fine-grained measures, syndrome by syndrome or, better, by comparing multiple syndromes within the same study. The challenge is to achieve a better understanding of each syndrome's profile by reconstructing its changes as a function of CA or MA (Thomas et al., [<reflink idref="bib41" id="ref70">41</reflink>]). In the present work, cognitive level-related change in lexical knowledge was studied by distinguishing general vocabulary from relational vocabulary. The distinction between the two was made only quite recently in the study of language development of children with ID (Facon, Magis, & Courbois, [<reflink idref="bib18" id="ref71">18</reflink>]; Mervis & John, [<reflink idref="bib34" id="ref72">34</reflink>]; Miolo et al., [<reflink idref="bib35" id="ref73">35</reflink>]). The respective developmental trajectories of these two components of children's lexicon were thus not yet known.</p> <p>Four notable facts emerge from the two present studies. First, the strength of the relationship with RAVEN test scores is greater for the BOEHM (relational vocabulary) than for the EVIP (general vocabulary). This confirms the idea that relational and general vocabulary must be distinguished with respect to their dependence on cognition (Fazio et al., [<reflink idref="bib22" id="ref74">22</reflink>]). Specifically, relational words are more difficult for the child to comprehend because these words have less stable and tangible relationships with their referents (Boehm, [<reflink idref="bib1" id="ref75">1</reflink>]). Their learning thus requires the ability to extract their meaning across multiple contexts – in short, to generalise (French & Nelson, [<reflink idref="bib23" id="ref76">23</reflink>]). The relational vocabulary, in turn, is decisive with regard to the development of problem-solving skills and, more generally, abstract thought (Boehm, [<reflink idref="bib4" id="ref77">4</reflink>]). The difference between the BOEHM and the EVIP in relation to the RAVEN was significant in Study 1. The results for Study 2 were in the same direction but nonsignificant because of low statistical power.</p> <p>Second, the parallel EVIP regression lines of TD participants and participants with UND on the one hand, and of TD participants and participants with DS on the other, indicate that the developmental trajectory of general vocabulary as a function of cognitive level is similar regardless of diagnostic status. In contrast, the scores on the EVIP of participants with UND and participants with DS are significantly greater than those of TD participants. This confirms the finding, often described in the literature, that general vocabulary is a strength for people with ID relative to their general developmental level (Chapman, [<reflink idref="bib6" id="ref78">6</reflink>]; Facon et al., [<reflink idref="bib16" id="ref79">16</reflink>]). From this standpoint, the present work extends the finding by showing that this relative advantage is constant whatever the children's nonverbal cognitive level. Comparison of the two present studies shows that the diagnostic status effect size is far greater for participants with UND than for participants with DS. In others words, general vocabulary strength is more marked for the former than for the latter. As this strength probably originates in CA-related experience (Chapman, [<reflink idref="bib6" id="ref80">6</reflink>]; Facon et al., [<reflink idref="bib16" id="ref81">16</reflink>]), the observed effect size difference could mean that, compared with other participants with ID, participants with DS have more difficulty capitalising on their experience for acquiring new words. The significant group difference observed in Study 2 between the EVIP scores of participants with UND and participants with DS strengthens this interpretation.</p> <p>Third, in Study 1 the two groups' mean performance on the BOEHM is of the same order of magnitude (no group effect). By contrast, the BOEHM scores of TD participants appear higher than those of participants with UND in the lower range of cognitive levels, whereas the reverse is observed in the upper range. This significant RAVEN × diagnostic status interaction means that the rate of development of relational vocabulary is, all other things being equal, faster for the participants with ID. However, given its small effect size, this phenomenon should not be overemphasised or overinterpreted. One may hypothesise, however, that it could result from age-related educational experience. Specifically, it is possible that, in the upper range of cognitive levels, the higher CA of participants with UND, and thus their greater exposure to experience, gives them a slight but significant advantage over their TD counterparts in the mastery of relational concepts.</p> <p>Fourth, the difference between BOEHM scores of TD participants and participants with DS approaches significance, a result of potential importance because of the small samples involved. Indeed, with only 45 participants per group, the robustness and power of most statistical tests is rather limited. In this respect, it is safe to conclude that, compared to TD children of the same cognitive level, those with DS have a slight but real developmental delay in their relational lexicon coexisting with a relative advance in their general vocabulary. This, of course, remains to be confirmed, and for the present we can only note that this interpretation is favoured by the significant difference between participants with UND and participants with DS noted in Study 2.</p> <p>One potential problem of this work concerns the use of between-subject comparisons to examine the development of lexical competence relative to cognitive level. The limitations of cross-sectional analyses are well known, and a longitudinal approach is certainly preferable (Karmiloff-Smith, [<reflink idref="bib30" id="ref82">30</reflink>]). However, all cross-sectional data are not necessarily corrupted by the potential bias attributed to cross-sectional designs, and the longitudinal approach itself is not without flaws (Shadish, Cook, & Campbell, [<reflink idref="bib39" id="ref83">39</reflink>]). As suggested by Hertzog ([<reflink idref="bib25" id="ref84">25</reflink>]), one of the best ways to study development is to begin with comparisons of extreme-age groups, continue with full cross-sectional studies, and then extend the analyses with longitudinal or cross-sequential designs (see also Thomas et al., [<reflink idref="bib41" id="ref85">41</reflink>]). Thus, the next stage of this study might well take a longitudinal or cross-sequential approach to confirm and extend the present findings.</p> <p>The fact that the present work concerns only participants with UND and participants with DS constitutes another potential limitation, especially from the standpoint of generalisation. Thus, it will be well to follow up the study by conducting comparable analyses with other aetiological groups (e.g., FXS, WS) in order to determine whether or not the present results hold regardless of the origin of ID. In this respect, it appears that children with WS have a relational vocabulary below their nonverbal reasoning level and well below their general vocabulary, and that this profile seems stable from a developmental viewpoint (Mervis, [<reflink idref="bib33" id="ref86">33</reflink>]).</p> <p>A further limitation of the study is the lack of solid data on parental education and socioeconomic status (SES). As parental education and family SES are related to language development among TD children (Hoff, [<reflink idref="bib28" id="ref87">28</reflink>]) and those with ID (Price et al., [<reflink idref="bib36" id="ref88">36</reflink>]), parental education and SES should certainly be considered as covariates in future studies of language development of people with ID.</p> <p>In the present work, participants' cognitive levels ranged from about 3 to 7 years. This span lies within the target age ranges of the tests used, in particular the RAVEN, which is not suitable for younger children, and the BOEHM, which is normed only through 8 years of age but already pushed the ceiling in Study 1. Further studies are thus needed to complete our knowledge of how the lexicon evolves both below and above the present age range. In this regard, it will be of interest to determine when the developmental gap between relational and general vocabulary begins to appear or whether it exists from the very beginning of lexical development.</p> <hd id="AN0114435074-15">Acknowledgements</hd> <p>We are grateful to John M. Belmont for his helpful comments on this manuscript. We also thank the students and psychologists who helped with data collection. 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  Label: Title
  Group: Ti
  Data: A Cross-Sectional Analysis of Developmental Trajectories of Vocabulary Comprehension among Children and Adolescents with Down Syndrome or Intellectual Disability of Undifferentiated Aetiology
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  Label: Language
  Group: Lang
  Data: English
– Name: Author
  Label: Authors
  Group: Au
  Data: <searchLink fieldCode="AR" term="%22Facon%2C+Bruno%22">Facon, Bruno</searchLink><br /><searchLink fieldCode="AR" term="%22Courbois%2C+Yannick%22">Courbois, Yannick</searchLink><br /><searchLink fieldCode="AR" term="%22Magis%2C+David%22">Magis, David</searchLink>
– Name: TitleSource
  Label: Source
  Group: Src
  Data: <searchLink fieldCode="SO" term="%22Journal+of+Intellectual+%26+Developmental+Disability%22"><i>Journal of Intellectual & Developmental Disability</i></searchLink>. 2016 41(2):140-149.
– Name: Avail
  Label: Availability
  Group: Avail
  Data: Taylor & Francis. Available from: Taylor & Francis, Ltd. 530 Walnut Street Suite 850, Philadelphia, PA 19106. Tel: 800-354-1420; Tel: 215-625-8900; Fax: 215-207-0050; Web site: http://www.tandf.co.uk/journals
– Name: PeerReviewed
  Label: Peer Reviewed
  Group: SrcInfo
  Data: Y
– Name: Pages
  Label: Page Count
  Group: Src
  Data: 10
– Name: DatePubCY
  Label: Publication Date
  Group: Date
  Data: 2016
– Name: TypeDocument
  Label: Document Type
  Group: TypDoc
  Data: Journal Articles<br />Reports - Research
– Name: Audience
  Label: Education Level
  Group: Audnce
  Data: <searchLink fieldCode="EL" term="%22Kindergarten%22">Kindergarten</searchLink>
– Name: Subject
  Label: Descriptors
  Group: Su
  Data: <searchLink fieldCode="DE" term="%22Vocabulary+Development%22">Vocabulary Development</searchLink><br /><searchLink fieldCode="DE" term="%22Comprehension%22">Comprehension</searchLink><br /><searchLink fieldCode="DE" term="%22Children%22">Children</searchLink><br /><searchLink fieldCode="DE" term="%22Adolescents%22">Adolescents</searchLink><br /><searchLink fieldCode="DE" term="%22Down+Syndrome%22">Down Syndrome</searchLink><br /><searchLink fieldCode="DE" term="%22Intellectual+Disability%22">Intellectual Disability</searchLink><br /><searchLink fieldCode="DE" term="%22Cognitive+Ability%22">Cognitive Ability</searchLink><br /><searchLink fieldCode="DE" term="%22Clinical+Diagnosis%22">Clinical Diagnosis</searchLink><br /><searchLink fieldCode="DE" term="%22Correlation%22">Correlation</searchLink><br /><searchLink fieldCode="DE" term="%22Intelligence+Tests%22">Intelligence Tests</searchLink><br /><searchLink fieldCode="DE" term="%22Verbal+Ability%22">Verbal Ability</searchLink><br /><searchLink fieldCode="DE" term="%22Vocabulary%22">Vocabulary</searchLink><br /><searchLink fieldCode="DE" term="%22Kindergarten%22">Kindergarten</searchLink><br /><searchLink fieldCode="DE" term="%22Special+Schools%22">Special Schools</searchLink>
– Name: SubjectThesaurus
  Label: Assessment and Survey Identifiers
  Group: Su
  Data: <searchLink fieldCode="SU" term="%22Peabody+Picture+Vocabulary+Test%22">Peabody Picture Vocabulary Test</searchLink><br /><searchLink fieldCode="SU" term="%22Boehm+Test+of+Basic+Concepts%22">Boehm Test of Basic Concepts</searchLink><br /><searchLink fieldCode="SU" term="%22Raven+Progressive+Matrices%22">Raven Progressive Matrices</searchLink>
– Name: DOI
  Label: DOI
  Group: ID
  Data: 10.3109/13668250.2016.1160370
– Name: ISSN
  Label: ISSN
  Group: ISSN
  Data: 1469-9532
– Name: Abstract
  Label: Abstract
  Group: Ab
  Data: Background: In this work we sought to expand our knowledge of developmental trajectories of subcomponents of the language systems of individuals with intellectual disability (ID). We aimed to explore how "general" and "relational" vocabularies evolve as a function of cognitive level. Method: Developmental trajectories of general and relational vocabulary comprehension were compared among typically developing (TD) children and children and adolescents with ID of undifferentiated aetiology (UND) or Down syndrome (DS). Results: Comparisons between TD participants and participants with UND showed no interaction between cognitive level and diagnostic status for general vocabulary, and only a very weak interaction for relational vocabulary. Comparisons between TD participants and participants with DS failed to reveal group-specific trajectories. Performance in general vocabulary was higher than in relational vocabulary for participants with UND and DS. Conclusion: The developmental trajectories of vocabulary appear to be globally comparable for participants with or without ID.
– Name: AbstractInfo
  Label: Abstractor
  Group: Ab
  Data: As Provided
– Name: Ref
  Label: Number of References
  Group: RefInfo
  Data: 41
– Name: DateEntry
  Label: Entry Date
  Group: Date
  Data: 2018
– Name: AN
  Label: Accession Number
  Group: ID
  Data: EJ1188815
PLink https://search.ebscohost.com/login.aspx?direct=true&site=eds-live&db=eric&AN=EJ1188815
RecordInfo BibRecord:
  BibEntity:
    Identifiers:
      – Type: doi
        Value: 10.3109/13668250.2016.1160370
    Languages:
      – Text: English
    PhysicalDescription:
      Pagination:
        PageCount: 10
        StartPage: 140
    Subjects:
      – SubjectFull: Vocabulary Development
        Type: general
      – SubjectFull: Comprehension
        Type: general
      – SubjectFull: Children
        Type: general
      – SubjectFull: Adolescents
        Type: general
      – SubjectFull: Down Syndrome
        Type: general
      – SubjectFull: Intellectual Disability
        Type: general
      – SubjectFull: Cognitive Ability
        Type: general
      – SubjectFull: Clinical Diagnosis
        Type: general
      – SubjectFull: Correlation
        Type: general
      – SubjectFull: Intelligence Tests
        Type: general
      – SubjectFull: Verbal Ability
        Type: general
      – SubjectFull: Vocabulary
        Type: general
      – SubjectFull: Kindergarten
        Type: general
      – SubjectFull: Special Schools
        Type: general
      – SubjectFull: Peabody Picture Vocabulary Test
        Type: general
      – SubjectFull: Boehm Test of Basic Concepts
        Type: general
      – SubjectFull: Raven Progressive Matrices
        Type: general
    Titles:
      – TitleFull: A Cross-Sectional Analysis of Developmental Trajectories of Vocabulary Comprehension among Children and Adolescents with Down Syndrome or Intellectual Disability of Undifferentiated Aetiology
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            NameFull: Courbois, Yannick
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            NameFull: Magis, David
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            – TitleFull: Journal of Intellectual & Developmental Disability
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