Discrepancy Between Verbal and Nonverbal Ability
Traditional discrepancy criteria for SLI suggest that there should be a dis- crepancy between language age and both chronological age and mental age in children with SLI (Aram, Morris, & Hall, 1992; Stark & Tallal, 1981; Tallal, 1988). Data from our cohort study were available for 233 children (9 chil- dren had missing Raven’s scores as described in the prior section). Fifty- eight children (25%) had both nonverbal abilities and all language test scores within the normal range (above one standard deviation below the mean or 15.9 percentiles). Of these 58 children, 83% (48 children) had non- verbal-language scores at least 40 percentiles above language scores, thus fitting the traditional discrepancy criteria for SLI. Ten children (17%) did not meet the 40 percentile discrepancy criteria between verbal and nonver- bal scores. We followed 9 of those 10 children the year after and found that 5 had fully integrated into regular mainstream education, suggesting that this small group of children recovered after intervention.
This left 175 children who had at least one test of language below 15.9 percentiles. Of these 175 children, 85% (n = 148) had nonverbal cognitive scores within one standard deviation of the mean (above 15.9 percentiles), thus these 148 children met the traditional discrepancy criteria for SLI. Fourteen percent of the children (n = 24) had nonverbal cognitive abilities between one and two standard deviations below the mean (between 15.9 and 2.6 percentiles) making it difficult to apply the discrepancy criteria. Both IQ and language test scores were between one and two standard de- viations below the mean for these children. Finally, only three children scored below two standard deviations below the mean (2.5 percentiles or less) in the nonverbal test and also did poorly in the language tests. It was thought that these children were more globally delayed.
In summary, most of the children attending language units (196 out of 233 or 84%) met the traditional discrepancy criteria for SLI (for further de- tails, see Conti-Ramsden & Botting, 1999). The results of the present inves- tigation clarify that language units in England cater for children with SLI who have normal cognitive abilities. The percentage of children with global delays in language units was extremely small (1%).
1. CHILDREN WITH LANGUAGE IMPAIRMENT 25
TABLE 1.1
Assessment Means, Standard Deviations, and 95% Confidence Intervals for the Entire Sample
Test for Reception of Grammar BAS Naming Vocabulary Goldman–Fristoe Test of Articulation Renfrew Bus Story Raven’s Matrices Mean (SD) 95% CI 20.0 (19.9) 17.8 to 23.4 32.1 (25.6) 30.2 to 37.2 41.9 (33.6) 37.3 to 46.3 18.5 (19.1) 16.5 to 21.8 61.9 (29.5) 58.0 to 66.0
In Search of Language Impairment Profiles
The data used to establish subgroups of children came from two sources: results from standardized tests and information from a teacher/speech- language pathologist interview. We thought it would be particularly use- ful to see how much information could be obtained from a single assess- ment session, such as would be feasible in a clinical setting. This ruled out lengthy procedures involving a number of sessions with each child or the collection of spontaneous language samples. We chose breadth rather than depth of assessment and selected the following test battery:
1. Test for Reception of Grammar (TROG; Bishop, 1982). This oral com- prehension test presents children with four pictures while the examiner reads a sentence. Each child is asked to pick the picture that illustrates the sentence. These items begin very simply, with four distinct objects and one word read out, and progress to complex grammar structures (e.g., “The cat the cow chases is black”). Items are organized into blocks of four grammatically related sentences. The child must answer all four correctly to pass the block. After five consecutive blocks have been failed, the test is discontinued. The number of blocks passed is then noted and transformed into age-adjusted percentile ranges (e.g., 5th–10th percentile). For ease of statistical comparison, in the present study, these ranges have been trans- formed further into midpoint percentiles for that range (e.g., 5th–10th per- centile becomes 7.5th percentile).
2. Three Subtests of the British Ability Scales (BAS; Elliot, 1983). Number skills. Children are presented with picture cues and asked to perform calculations. These range in complexity and include counting, finding similarities, simple addition, subtraction, multiplication and divi- sion, matching figures to groups of objects, and tests of concepts. Re- sponses are scored as correct or incorrect, and the test is discontinued once the child has answered five questions incorrectly. The number of correct answers is summed and a percentile for age recorded.
Naming vocabulary. Children are asked to name a series of pictures of everyday objects. Responses are scored as correct or incorrect, and testing is discontinued after the child has named five items incorrectly. The num- ber of correct answers is summed and a percentile for age recorded.
Word reading. Children are presented with a list of single words and asked to read them out loud. This assessment measures only single- word sight reading and is not designed to assess reading comprehension or fluency. Testing is discontinued after 10 incorrect attempts. The total number of correctly read words is summed and transformed into a per- centile for age.
3. Goldman–Fristoe Test of Articulation (Goldman & Fristoe, 1986). Again children are asked to name a series of pictures of everyday items. Children