ABSTRACT
What Is the ABD Model? 56 Original ABD Concept Was Based on Three Facets of LD Research 58
Frequency of Overlapping Disorders 58 Genetic and Environmental Etiologic Variability in
Learning Disorders 61 Variable Neuroanatomy of Developmental Disorders 63
The Case Against the ABD Model 64 The ABD Concept Revisited 65
1. Whole-Brain Perspective 65 2. Variation Can Be “Normal” 66 3. Redefinition of Behavioral Phenotypes in Terms of
Neurological Basis 67 4. ABD Is Developmentally Reasonable 67 5. Avoidance of One-Size-Fits-All Way of Thinking 69 6. Treatment That Is Specific to Individual Profiles 70 7. Applicability to Adults With Learning Disabilities 71
Some Diagnostic Implications of ABD 72 Conclusion 74 References 75
At the International Congress of Psychology in 2000, we presented a paper on the concept of atypical brain development (ABD) (Lyytinen, 2000) as part of a joint session on learning disabilities and neuropsychology. Subsequently, some of the papers from this conference were published in the journal Developmental Neuropsychology (Gilger & Kaplan, 2001), including a commentary by Utta Frith on theories of the etiology of developmental learning disorders (LD). Since that time, the ABD concept has been discussed, applied, and debated by ourselves and others (e.g., Gilger & Wise, 2004; Rice & Brooks, 2004; Kaplan, Dewey, Crawford, & Wilson, 2001; Fadjukoff, Ahonen, & Lyytinen, 2001; Frith, 2001; Bonifacci, 2004; Goldstein & Schwebach, 2004; Jeffries & Everatt, 2004; Sonuga-Barke, 2003; Valtonen, Ahonen, Lyytinen, & Lyytinen, 2004; Lyon, Fletcher, & Barnes, 2003; Davis, 2004; Gilger, Hynd, & Wilkins, in press).
