UNIVERSITÀ DEGLI STUDI DI VERONA DIPARTIMENTO DI FILOLOGIA, LETTERATURA E LINGUISTICA DOTTORATO DI RICERCA IN LINGUISTICA CICLO XXIII DDiisseennttaanngglliinngg DDyysslleexxiiaa Phonological and Processing Impairment in Developmental Dyslexia s.s.d. L-LIN/01 Coordinatore: Prof.ssa Camilla Bettoni Tutor: Prof. Denis Delfitto Dottorando: Dott.ssa Maria Vender March 15, 2011 Table of Contents TABLE OF CONTENTS................................................................................................................ 3 ABSTRACT .............................................................................................................................. 11 ACKNOWLEDGMENTS ............................................................................................................. 15 INTRODUCTION ...................................................................................................................... 17 1 AN INTRODUCTION TO DEVELOPMENTAL DYSLEXIA ........................................................... 23 1.1 INTRODUCTION ....................................................................................... 23 1.2 ON THE DIFFICULTY TO FIND A COMPREHENSIVE DEFINITION OF DEVELOPMENTAL DYSLEXIA .............................................................................................. 26 1.3 MANIFESTATIONS OF DEVELOPMENTAL DYSLEXIA ........................................... 29 1.3.1 Reading difficulties .................................................................................................... 29 1.3.1.1 Reading skills in developmental dyslexia ......................................................................... 29 1.3.1.2 A theoretical approach to reading: the Dual-Route Model .............................................. 31 1.3.1.3 The development of reading: Frith’s model of learning to read ...................................... 36 1.3.2 Spelling difficulties .................................................................................................... 40 1.3.3 Language deficits ...................................................................................................... 42 1.3.3.1 Phonological deficits ........................................................................................................ 42 1.3.3.2 Vocabulary development and lexical retrieval ................................................................. 45 1.3.3.3 Grammatical deficits ........................................................................................................ 47 1.3.3.3.1 Dyslexia and the Interpretation of Tough Sentences .............................................. 48 1.3.3.3.2 Dyslexia and the Interpretation of Pronouns .......................................................... 50 1.3.3.3.3 Dyslexia and the Interpretation of Relative Clauses ................................................ 57 1.3.3.3.4 Dyslexia and the Interpretation of Passive Sentences ............................................ 62 1.3.3.3.5 Dyslexia and the Interpretation of Grammatical Aspect ......................................... 64 1.3.3.3.6 Dyslexia and Morphosyntactic Agreement ............................................................. 65 1.3.4 Attention deficits ....................................................................................................... 67 1.3.5 Motor deficits ............................................................................................................ 71 1.4 PRECURSORS OF DYSLEXIA......................................................................... 75 1.5 THE NEUROBIOLOGY OF DYSLEXIA ............................................................... 78 1.6 SUMMARY AND CONCLUSION .................................................................... 83 2 DEVELOPMENTAL DYSLEXIA: THEORETICAL PERSPECTIVES ................................................. 87 2.1 INTRODUCTION ....................................................................................... 87 2.2 THE VISUAL DEFICIT HYPOTHESIS ................................................................ 89 2.3 THE AUDITORY DEFICIT HYPOTHESIS ............................................................ 90 2.4 THE MAGNOCELLULAR DEFICIT HYPOTHESIS .................................................. 92 2.4.1 The Magnocellular Systems and its disruption in Dyslexia ........................................ 92 2.4.2 Reading deficits as a consequence of magnocellular disorders ................................ 94 2.5 THE PHONOLOGICAL DEFICIT HYPOTHESIS ..................................................... 95 2.5.1 Deficit or delay? The Developmental Lag Hypothesis ............................................... 96 2.5.2 Phonological deficits causing or caused by poor reading? ........................................ 98 2.5.3 Underspecified phonological representations or difficulties accessing them? .......... 99 2.5.4 Strengths and weaknesses of the Phonological Deficit Hypothesis ........................ 102 2.6 THE DOUBLE DEFICIT HYPOTHESIS ............................................................. 104 2.7 THE WORKING MEMORY DEFICIT HYPOTHESIS ............................................. 107 2.7.1 What is Working Memory? ..................................................................................... 108 2.7.2 Baddeley and Hitch’s Original Model of Working Memory ..................................... 110 2.7.2.1 The Phonological Loop ................................................................................................... 111 2.7.2.1.1 The Phonological Loop and Language Competence: evidence from language disordered and language gifted people ............................................................. 118 2.7.2.2 The Visuo-Spatial Sketchpad .......................................................................................... 120 2.7.2.3 The Central Executive .................................................................................................... 122 2.7.2.4 The Episodic Buffer ........................................................................................................ 124 2.7.3 Baddeley’s revised Model of Working Memory ...................................................... 125 2.7.4 Working Memory and Development ....................................................................... 127 2.7.5 Working Memory, Cognitive Skills and Neuro-developmental Disorders ................ 129 2.7.5.1 Working Memory and Dyslexia ...................................................................................... 133 2.8 SUMMARY AND CONCLUSIONS ................................................................. 139 3 WORKING MEMORY SKILLS IN DEVELOPMENTAL DYSLEXIA ............................................. 143 3.1 INTRODUCTION ..................................................................................... 143 3.2 PARTICIPANTS ...................................................................................... 146 3.3 RESEARCH QUESTIONS AND PREDICTIONS ................................................... 147 3.4 GENERAL DESIGN AND PROCEDURE ........................................................... 148 3.4.1 Task 1: Digit Recall .................................................................................................. 149 3.4.1.1 Design and Procedure .................................................................................................... 149 3.4.2 Task 2: Word List Matching ..................................................................................... 150 3.4.2.1 Design and Procedure .................................................................................................... 150 3.4.3 Task 3: Word List Recall .......................................................................................... 151 3.4.3.1 Design and Procedure .................................................................................................... 151 3.4.4 Task 4: Block Recall ................................................................................................. 152 3.4.4.1 Design and Procedure .................................................................................................... 152 3.4.5 Task 5: Nonword List Recall..................................................................................... 154 3.4.5.1 Design and Procedure .................................................................................................... 154 3.4.6 Task 6: Listening Recall Task ................................................................................... 155 3.4.6.1 Design and Procedure .................................................................................................... 155 3.4.7 Task 7: Counting Recall ........................................................................................... 156 3.4.7.1 Design and Procedure .................................................................................................... 156 3.4.8 Task 8: Mazes Memory Task ................................................................................... 158 3.4.8.1 Design and Procedure .................................................................................................... 158 3.4.9 Task 9: Backward Digit Recall Task ......................................................................... 159 3.4.9.1 Design and Procedure .................................................................................................... 159 3.5 GENERAL RESULTS ................................................................................