Children with Specific Language Impairment: Progress Toward a Grammatical Phenotype

1. Children with Specific Language Impairment: Progress Toward a Grammatical Phenotype Presentation by Mabel L. Rice Georgia State University March 18, 2002

2. Background: What are the Mechanisms That Underlie Children’s Acquisition of Morphosyntax? • Assumption of uniform robustness: All “normal” children acquire language effortlessly, following the same timing mechanisms and the same general sequence. An emphasis on invariant properties of language acquisition.  • “In general, language acquisition is a stubbornly robust process; from what we can tell there is virtually no way to prevent it from happening short of raising a child in a barrel.” Pinker, 1984, p. 29.

3. Updated assumption: Otherwise “normal” children can have language impairments (SLI); there is unexpected and unexplained variance across children. • Some relatively invariant properties of morphosyntax show unexpected individual variability

4. Two Kinds of Variation Across Children 2.1 Background: Conventional notion of variation • “normative” variation • referenced to age expectations • bell-shaped curve

5. Number of Children Performance Level

6. Two Kinds of Variation Across Children 2.1 Background: Conventional notion of variation • “normative” variation • referenced to age expectations • bell-shaped curve • definition of “SLI” • definition of “language disordered”

7. Number of Children Performance Level

9. 2.2 Variation in onset timing: Late activation of language acquisition mechanisms?

10. A late start for an intact language system versus a late start for an underspecified grammar

12. The value of the 3-group design: Affected, age-matched, language-matched

13. The value of the 3-group design: Affected, age-matched, language-matched • Affected < Age matches = “Language Impairment”

14. The value of the 3-group design: Affected, age-matched, language-matched • Affected < Age matches = “Language Impairment” • Affected < language-matched = “Language impairment beyond general language delay”

15. 2.3    Variation in acquisition timing mechanisms for TNS, ages 3-8 years • SLI children start later, and show slower acquisition timing although similar growth curves

16. 2.3    Variation in acquisition timing mechanisms for TNS, ages 3-8 years • SLI children start later, and show slower acquisition timing although similar growth curves • Performance Data

18. 2.3    Variation in acquisition timing mechanisms for TNS, ages 3-8 years • SLI children start later, and show slower acquisition timing although similar growth curves • Performance Data • Comprehension Data

20. Young children show variation that disappears by age 5 years, at adult grammar • Performance Data

22. Young children show variation that disappears by age 5 years, at adult grammar • Comprehension Data

24. SLI children show variation in a range far below age expectations

26. 3. At the same time of variation in TNS- marking, other morphology is nonvariant

27. 4. Lexical indices Show Consistent Variation Across the Growth Curve, and Do Not Differentiate SLI from Language-Equivalent Group • # Different Words

29. 4. Lexical indices Show Consistent Variation Across the Growth Curve, and Do Not Differentiate SLI from Language-Equivalent Group • # Different Words • # Verb Types

31. 4. Lexical indices Show Consistent Variation Across the Growth Curve, and Do Not Differentiate SLI from Language-Equivalent Group • # Different Words • # Verb Types • # Verb Tokens

33. 4. Lexical indices Show Consistent Variation Across the Growth Curve, and Do Not Differentiate SLI from Language-Equivalent Group • # Different Words • # Verb Types • # Verb Tokens • % General All Purpose Verbs

35. 4. Lexical indices Show Consistent Variation Across the Growth Curve, and Do Not Differentiate SLI from Language-Equivalent Group • # Different Words • # Verb Types • # Verb Tokens • % General All Purpose Verbs • PPVT Raw Scores

37. 5. Detection of Variability in TNS Acquisition Requires Indices that Capture the Probabilistic Character of Optionality

38. 5. Detection of Variability in TNS Acquisition Requires Indices that Capture the Probabilistic Character of Optionality • Emergence measures such as Index of Production Syntax (IPSYN) are not sensitive to grammar markers

40. 5. Detection of Variability in TNS Acquisition Requires Indices that Capture the Probabilistic Character of Optionality • Emergence measures such as Index of Production Syntax (IPSYN) are not sensitive to grammar markers • Composite indices such as Developmental Sentence Scoring are not sensitive to grammar markers

42. 6. Timing of Acquisition Differs for Morphosyntactic and Morphonological Components of TNS-Marking

43. 6. Timing of Acquisition Differs for Morphosyntactic and Morphonological Components of TNS-Marking • “walked” as finite in morphosyntax • “runned” as finite • “ran” as finite + morphophonologically accurate

47. 7. Growth Curve Components and Predictors of Growth are Similar for TNS/Finiteness Indices, but Differ from Morphophonological Index • TNS Productions Linear and quadraticcomponents for SLI and MLU groups; same curves for both groups Non-Predictors: Intelligence, vocabulary (PPVT-R), Mother’s education Predictor: MLU

48. Irregular Past Tense Linear growth only, for both groups Non-predictors: Mother’s education Predictors: MLU, vocabulary, intelligence • Finite past tense Linear and quadratic components for SLI and MLU groups; same curves for both groups Non-predictors: Intelligence, vocabulary, and mother’s education Predictor: MLU

49. Conclusions: TNS/AGR-marking (finiteness) follows growth curves that are linear + quadratic in shape and growth is not predicted by intelligence, vocabulary, or mother’s education, and is positively predicted by MLU, although not strongly. When morphophonological accuracy is included in the measurement, the growth curve becomes linear only and the predictors shift to include a child’s vocabulary and non-verbal intelligence.