On the Developmental Trajectories of Relational Concepts Among Children and Adolescents With Intellectual Disability of Undifferentiated Etiology.

The aim of this study was to examine the developmental trajectories of comprehension of relational concepts among 557 participants with intellectual disability (ID) of undifferentiated etiology (M age  =  12.20 years, SD  =  3.18) and 557 typically developing (TD) participants (M age  =  4.57 years, SD  =  0.80). Logistic regression analyses, with nonverbal cognitive level entered first in the equations, showed only negligible differences with regard to the discriminative power of each of the 72 concepts used as outcome variables, and moderate differences in difficulty for only three items. A moderate mixed effect (i.e., combining a group difference in difficulty and discriminative power) was observed for a fourth item. It is concluded that the developmental trajectories of relational concepts are similar for participants with or without ID. The implications and limitations of the study are discussed.

Does the Development of Syntax Comprehension Show a Premature Asymptote Among Persons With Down Syndrome? A Cross-Sectional Analysis.

Uncertainty persists regarding the post-childhood trajectory of syntactic acquisition of persons with Down syndrome (DS). In some studies, asymptote is reached in the early teens, whereas others find syntax continuing to develop at least into early adulthood. This study addressed the issue using a cross-sectional approach. Receptive syntax and vocabulary were tested in 62 children, adolescents and young adults with DS matched on chronological age and cognitive level with 62 participants with intellectual disability (ID) of undifferentiated etiology. On both tests there were significant effects of chronological age and diagnosis, but the chronological age × diagnosis interactions were nonsignificant. We concluded that comprehension of vocabulary and syntax does not asymptote prematurely in individuals with DS relative to those with other forms of ID.

An Item Analysis of the French Version of the Test for Reception of Grammar Among Children and Adolescents With Down Syndrome or Intellectual Disability of Undifferentiated Etiology.

Purpose: An item analysis of Bishop's (1983) Test for Reception of Grammar (TROG) in its French version (F-TROG; Lecocq, 1996) was conducted to determine whether the difficulty of items is similar for participants with or without intellectual disability (ID). Method: In Study 1, responses to the 92 F-TROG items by 55 participants with Down syndrome (DS), 55 with ID of undifferentiated etiology (UND), and 55 typical children (TYP) matched on their F-TROG total score were compared using the transformed item difficulties method, a statistical approach designed to detect differential item functioning (DIF) between groups. In Study 2, an additional comparison involving 526 TYP participants and 526 participants with UND was conducted to increase the statistical power of the analysis. Results: The difficulty of items was highly similar whatever the sample size or clinical status of participants. Fewer than 3.5% of the items were flagged as showing DIF. Conclusions: Tests such as the TROG can be used with confidence in clinical practice as well as in research studies comparing participants with or without ID. Methods designed for investigating potential internal test bias-such as done here-should be more regularly employed in the developmental disability field to affirm the absence of DIF.

A qualitative analysis of general receptive vocabulary of adolescents with Down syndrome.

This study aimed to discover whether general receptive vocabulary is qualitatively phenotypical in Down syndrome. Sixty-two participants with Down syndrome (M age=16.74 years, SD=3.28) were individually matched on general vocabulary raw total score with 62 participants with intellectual disability of undifferentiated etiology (M age=16.20 years, SD=3.08) and 62 typical children (M age=5.32 years, SD=0.82). Item analyses using the transformed item difficulties method to detect differential item functioning across groups showed that the groups' rank orders of item difficulty were highly similar. It was concluded that the general receptive vocabulary of older children and adolescents with Down syndrome is not qualitatively distinguished when its overall size is held constant. Methodological and theoretical implications of this finding are discussed.

Angoff's delta method revisited: improving DIF detection under small samples.

Most methods for detecting differential item functioning (DIF) are suitable when the sample sizes are sufficiently large to validate the null statistical distributions. There is no guarantee, however, that they will still perform adequately when there are few respondents in the focal group or in both the reference and the focal group. Angoff's delta plot is a potentially useful alternative for small-sample DIF investigation, but it suffers from an improper DIF flagging criterion. The purpose of this paper is to improve this classification rule under mild statistical assumptions. This improvement yields a modified delta plot with an adjusted DIF flagging criterion for small samples. A simulation study was conducted to compare the modified delta plot with both the classical delta plot approach and the Mantel-Haenszel method. It is concluded that the modified delta plot is consistently less conservative and more powerful than the usual delta plot, and is also less conservative and more powerful than the Mantel-Haenszel method as long as at least one group of respondents is small.

On the difficulty of relational concepts among participants with Down syndrome.

The aim of the study was to compare the difficulty of relational concepts among participants with and without intellectual disability. The French versions of the Boehm Tests of Basic Concepts Third Edition (Preschool and Kindergarten to 2nd grade) were administered to three groups of 47 participants individually matched on their total raw score on the tests. The first group comprised participants with intellectual disability of undifferentiated etiology, the second, participants with Down syndrome and the third, typical children. Item analyses using the transformed item difficulties method to detect differential item functioning across groups showed that the groups' rank-orders of item difficulty were highly similar. It is concluded that, all things being equal, relational concepts are of comparable difficulty and follow a similar sequence of development whatever the cognitive and etiological status of participants. Methodological and theoretical implications of these findings are discussed.

Beyond matching on the mean in developmental disabilities research.

The matching of groups is a traditional way to control for confounding variables in developmental disabilities research. The equivalency of means across groups is routinely checked for these variables, but not the homogeneity of their variances or the shapes of their distributions. In the present paper, it is argued that group matching can go seriously wrong unless it directly confronts the distributional concerns by the use of well-known statistical indices and very simple graphical displays of the distributions. The question of the equivalency of item response profiles is also addressed since two participants or two groups of participants can obtain the same overall score on the matching variable by passing different items. In this case, the matching cannot be considered satisfactory because of poor concordance between the molar (overall score) and molecular (item scores) levels of matching. Angoff's Delta plot method, a statistical approach for detecting differential item functioning across small groups is described. It is promising as a simple way to prove whole test/individual item correspondence and, in addition, a useful tool for making post hoc statistical analyses at the item level on the dependent variables.

Increasing compliance with medical examination requests directed to children with autism: effects of a high-probability request procedure.

The purpose of this study was to evaluate the effectiveness of a high-probability (high-p) request sequence as a means of increasing compliance with medical examination tasks. Participants were children who had been diagnosed with autism and who exhibited noncompliance during general medical examinations. The inclusion of the high-p request sequence effectively increased compliance with medical examination tasks. In addition, the procedure was efficient, could be implemented by parents and medical professionals, and did not involve aversive procedures.

An item analysis of Raven's Colored Progressive Matrices among participants with Down syndrome.

Standardized tests are widely used in intellectual disability research, either as dependent or control variables. Yet, it is not certain that their items give rise to the same performance in various groups under study. In the present work, 48 participants with Down syndrome were matched on their raw score on Raven's Colored Progressive Matrices (RCPM) with 48 participants with intellectual disability of undifferentiated etiology and 48 typical children. An item analysis was then conducted using the transformed item difficulties method, a statistical approach designed to detect differential item functioning between groups. Results showed that the difficulty of items was highly similar for the three groups. It is concluded that RCPM can be used with considerable confidence in comparative studies including typical, Down syndrome and intellectually disabled participants of undifferentiated etiology. Some methodological implications of these findings are discussed.

A controlled single-case treatment of severe long-term selective mutism in a child with mental retardation.

The aim of the present study was to demonstrate the efficacy of combining two operant learning procedures--shaping and fading--for treating selective mutism. The participant was a 12-year-old boy with mental retardation presenting a severe long-term selective mutism. The treatment was aimed at increasing the loudness of his vocalizations in an increasingly social milieu. The treatment was conducted over the course of about 20 weeks, with four 15-minute sessions per week. A gradual increase in speech loudness was observed. Data indicated a close correspondence between the changes in speech loudness and the criteria for reinforcement successively applied by the therapist, thereby confirming the causal link between the child's progress and the changes in reinforcement contingencies. In addition, good generalization was noted during the stimulus fading phase. Six-month follow up showed that loudness of verbalizations was still satisfactory in the classroom despite a change of school and peer group. The impressive improvement of the child's verbal behavior shows that the implementation of a treatment package including both shaping and stimulus fading is a worthwhile therapeutic option, even in the case of severe long-term selective mutism associated with mental retardation.

A cross-sectional test of the similar-trajectory hypothesis among adults with mental retardation.

The similar-sequence and the similar-structure hypotheses are the two mainstays of the developmental approach to mental retardation. In the present study, a third way, the similar-trajectory hypothesis, is described and illustrated using the WAIS-R results of adults with and without mental retardation aged from 20 to 54 years. The whole sample (N=633) comprised 306 participants with mental retardation and 327 without mental retardation. Hierarchical regression analyses comparing the two groups showed similar evolutions of scores with increasing age for verbal and performance scales. These results seem to validate the similar-trajectory hypothesis, at least for the present samples and for the aspects of cognitive development considered here. Some weaknesses and implications of the study are considered in the discussion.

The reinforcing effect of contingent attention on verbal perseverations of two children with severe visual impairment.

The frequency of verbal perseverations of two children with severe visual impairment was reduced using differential reinforcement of appropriate speech coupled with extinction of perseverative utterances. A reversal design in which baseline and intervention were alternated in an A-B-A-B sequence was employed to show the functional relationship between the target behaviors and the treatment procedure. There was a marked increase in appropriate utterances and a correlated decrease in perseverative ones. These findings suggest that this singular feature of the language of certain children with visual impairment is, under natural conditions, probably maintained by the attention provided by their caregivers.

Chronological age, receptive vocabulary, and syntax comprehension in children and adolescents with mental retardation.

This study was designed to examine the association of CA with syntax and vocabulary comprehension in children and adolescents with mental retardation. It was conducted using the PPVT-R and the Test for Reception of Grammar. The cognitive level of participants was estimated by means of three nonverbal intelligence tests. Results indicated that scores on intelligence tests account for 55% and 29% of the variability of syntax and vocabulary scores, respectively. For the vocabulary, the introduction of CA into the regression equation produced a significant increment of the variance explained (17%). However, its contribution to the variance of the syntax test was not significant. This finding suggests that CA-related experience is linked to on the receptive vocabulary of children and adolescents with mental retardation.