title: Cognitive, environmental, and linguistic predictors of syntax in fragile X syndrome and Down syndrome.
abstract: OBJECTIVE
  To examine which cognitive, environmental, and speech-language variables predict expressive syntax in boys with fragile X syndrome (FXS), boys with Down syndrome (DS), and typically developing (TD) boys, and whether predictive relationships differed by group.
  
  
  METHODS
  We obtained Index of Productive Syntax (  Scarborough, 1990) scores for 18 boys with FXS only, 20 boys with both FXS and an autism spectrum disorder, 27 boys with DS, and 25 younger TD boys of similar nonverbal mental age. Predictors included group (diagnosis), nonverbal cognition, phonological working memory (PWM), maternal education, speech intelligibility, and expressive vocabulary. The research questions were addressed via hierarchical linear regression.
  
  
  RESULTS
  Diagnostic group, nonverbal cognition, and PWM predicted 56% of the variance in syntactic ability, with approximately three-fourths of the predicted variance explained by group membership alone. The other factors did not contribute any additional significant variance in this final model. There was no evidence that predictor effects differed by group.
  
  
  CONCLUSIONS
  Nonverbal cognition and PWM have an effect on expressive syntax beyond that of diagnostic group. These effects are estimated to be the same in boys with FXS, boys with DS, and TD boys. Explanations for residual variance and the relative role of different predictors are discussed.
authors.affiliation: University of North Carolina at Chapel Hill, NC, USA. estigarr@email.unc.edu
authors.forename: Bruno
authors.initials: B
authors.lastname: Estigarribia
authors.forename: Gary E
authors.initials: GE
authors.lastname: Martin
authors.forename: Joanne E
authors.initials: JE
authors.lastname: Roberts
mesh_terms: D000293:Adolescent; D002648:Child; D002659:Child Development Disorders, Pervasive / Q000175:diagnosis / Q000503:physiopathology*; D002675:Child, Preschool; D003071:Cognition / Q000502:physiology*; D004314:Down Syndrome / Q000175:diagnosis / Q000503:physiopathology*; D005260:Female; D005600:Fragile X Syndrome / Q000175:diagnosis / Q000503:physiopathology*; D006801:Humans; D007805:Language Development Disorders / Q000175:diagnosis / Q000503:physiopathology*; D016014:Linear Models; D008037:Linguistics; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology; D010700:Phonetics; D011237:Predictive Value of Tests; D012931:Social Environment; D013065:Speech Intelligibility / Q000502:physiology; D014705:Verbal Behavior / Q000502:physiology; D014825:Vocabulary