Using Developmental Trajectories to Understand Developmental Disorders Purpose In this article, the authors present a tutorial on the use of developmental trajectories for studying language and cognitive impairments in developmental disorders and compare this method with the use of matching. Method The authors assess the strengths, limitations, and practical implications of each method. The contrast ... Research Article
Research Article  |   April 01, 2009
Using Developmental Trajectories to Understand Developmental Disorders
 
Author Affiliations & Notes
  • Michael S. C. Thomas
    Birkbeck College, London
  • Dagmara Annaz
    University College London
  • Daniel Ansari
    University of Western Ontario, Canada
  • Gaia Scerif
    University of Oxford, United Kingdom
  • Chris Jarrold
    University of Bristol, United Kingdom
  • Annette Karmiloff-Smith
    Birkbeck College
  • Contact author: Michael Thomas, Developmental Neurocognition Laboratoy, School of Psychology, Birkbeck College, University of London, Malet Street, Bloomsbury, London WC1E 7HX, United Kingdom. E-mail: m.thomas@bbk.ac.uk.
Article Information
Development / Special Populations / Genetic & Congenital Disorders / Language Disorders / Social Communication & Pragmatics Disorders / Attention, Memory & Executive Functions / Language / Research Articles
Research Article   |   April 01, 2009
Using Developmental Trajectories to Understand Developmental Disorders
Journal of Speech, Language, and Hearing Research, April 2009, Vol. 52, 336-358. doi:10.1044/1092-4388(2009/07-0144)
History: Received July 6, 2007 , Revised January 7, 2008 , Accepted August 7, 2008
 
Journal of Speech, Language, and Hearing Research, April 2009, Vol. 52, 336-358. doi:10.1044/1092-4388(2009/07-0144)
History: Received July 6, 2007; Revised January 7, 2008; Accepted August 7, 2008

Purpose In this article, the authors present a tutorial on the use of developmental trajectories for studying language and cognitive impairments in developmental disorders and compare this method with the use of matching.

Method The authors assess the strengths, limitations, and practical implications of each method. The contrast between the methodologies is highlighted using the example of developmental delay and the criteria used to distinguish delay from atypical development.

Results The authors argue for the utility of the trajectory approach, using illustrations from studies investigating language and cognitive impairments in individuals with Williams syndrome, Down syndrome, and autism spectrum disorder.

Conclusion Two conclusions were reached: (a) An understanding of the underlying mechanism will be furthered by the richer descriptive vocabulary provided by the trajectories approach (e.g., in distinguishing different types of delay) and (b) an optimal design for studying developmental disorders is to combine initial cross-sectional designs with longitudinal follow-up.

Acknowledgment
This research was supported by U.K. Medical Research Council Grant G0300188 and European Commission (EC) Grant 0209088 (New and Emerging Science and Technology [NEST]) to Michael Thomas.
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