DESCRIBING THE EFFECT OF MOTOR ABILITY ON VISUAL-MOTOR SKILL ACQUISITION AND TASK PERFORMANCE IN CHILDREN WITH DEVELOPMENTAL COORDINATION DISORDER By Noémi Cantin A thesis submitted in conformity with the requirements for the degree of Doctor in Philosophy Graduate Department of Rehabilitation Science University of Toronto © Copyright by Noémi Cantin (2012) DESCRIBING THE EFFECT OF MOTOR ABILITY ON VISUAL-MOTOR SKILL ACQUISITION AND TASK PERFORMANCE IN CHILDREN WITH DEVELOPMENTAL COORDINATION DISORDER Noémi Cantin, Doctor in Philosophy (2012) Graduate Department of Rehabilitation Science, University of Toronto Abstract Background: For children with developmental coordination disorder (DCD), the acquisition and performance of everyday visual-motor activities such as buttoning, shoe tying, cutting with scissors or writing, presents a major challenge. Regardless of the activity considered, children with DCD are typically slower and less accurate than their peers. Given the well-acknowledged difficulties of children with DCD, it is surprising to find very few research studies systematically exploring visual-motor skill acquisition and performance in children with DCD. Objective: The overall objective of this study was to systematically describe visual-motor skill acquisition and task performance in children with DCD. Methods: Twenty-four children (8 years 11 months to 12 years 11 months) were recruited for this study; 12 children with DCD, 12 children developing typically with regards to their motor skills. A computer-based aiming task completed with three different cursor controls of increasing levels of difficulty (mouse, joystick, novel controller) was designed for this study. Mixed-effect modelling and visual graph analyses were performed to describe the influence of motor ability and task difficulty on visual-motor skill acquisition and task performance. ii Results: Motor ability modulated the impact of task difficulty on visual-motor skill acquisition and task performance. Children with DCD were as fast and as accurate as their peers in their initial performance of the simple, well-learned task (mouse). However, they were slower and less accurate when performing the complex and novel visual-motor task. Over repeated trials, the visual-motor task performance of children with DCD improved on all tasks, even for the simple. With regard to the complex, novel task, once children with DCD understood the features of the task, their performance also improved and approached that of their peers. Conclusion: While children with DCD can generally be characterized as less accurate and slower than their peers, this characterization needs to be specified and qualified; it is probably best not applied to a well-learned task. iii ACKNOWLEDGMENTS Where to start! So many years have gone by since I embarked on this journey! I have learned that during the course of a PhD, “life happens”, bringing with it its ups and downs. Many people have come and gone during this PhD, each helping in their different ways. They have enabled me to keep moving forward and to trust that one day, I would be sitting at my computer writing this last page, these last few words. I would first like to acknowledge the tremendous support I have received from my supervisor, Helene Polatajko. Her generosity towards her graduate students is remarkable. Knowing that, rain or shine, morning or night, she was always there for me kept me motivated and kept me writing even in the wee hours of the night. I also wish to acknowledge the support received from the members of my program advisory committee: Heather Carnahan, Tom Chau, Michelle Keightley, and Jennifer Ryan. I would like to thank Scott Young, then fellow PhD student in Biomedical Engineering at the University of Toronto. Our many discussions inspired the design of this study. I would like to recognize the work of Eric Wan who developed the computer program that was used in this thesis. I would also like to acknowledge the contribution of Malcolm Binns, statistician scientist at the Rotman Research Institute in Toronto. His guidance while I learned to perform mixed modelling was invaluable. I wish to acknowledge the numerous students that have contributed to this project through the years: Freda Goh, Alison Firestone, Megan Henze, Melodie Lumague, Jennifer Crouchman and He (Cherry) Ma. I also wish to sincerely thank the children and families that participated in my study, and everyone who helped in the recruitment process. Indeed, “life happened” during the course of this PhD. Striving to keep my family a priority throughout the process has helped me stay grounded and true to myself. Thank you for your understanding when late nights were making it hard to play hide- and-seek in the morning; merci grand-maman Diane for cutting and pasting for hours with Violette and for playing ‘rescue, rescue’ with Philippe; and a heartfelt thank you to my husband David for always being there for me and for believing that I would one day finish! iv TABLE OF CONTENTS Abstract ....................................................................................................................ii Acknowledgments ...................................................................................................iv Table of Contents .................................................................................................... v List of Tables............................................................................................................ix List of Figures .......................................................................................................... x List of Appendices .................................................................................................. xii 1 Introduction ...................................................................................................... 1 2 Background and Rationale ............................................................................... 6 2.1 Characterizing the Motor Abilities of Children with DCD ........................... 7 2.1.1 Motor Difficulties .......................................................................... 7 2.1.2 Visual-Motor Difficulties ............................................................... 9 2.2 Describing Visual-Motor Skill Acquisition and Task Performance in Children with DCD ........................................................................................ 11 2.2.1 Writing Tasks............................................................................. 12 2.2.2 Trail-Drawing Tasks .................................................................. 15 2.2.3 Fine Motor Aiming Tasks ........................................................... 16 2.2.4 Summary ................................................................................... 21 2.3 The Nature of Visual-Motor Skill Acquisition and Task Performance ...... 24 2.3.1 Task-Specific Features .............................................................. 25 2.3.2 Motor Control Mechanisms........................................................ 31 2.4 Investigating Visual-Motor Task Acquisition and Visual-Motor Task Performance in Children with DCD: Rationale and Research Objectives ..... 35 v 3 Methods ......................................................................................................... 38 3.1 Participants.............................................................................................. 38 3.2 Descriptive Measures .............................................................................. 42 3.3 Experimental Measure ............................................................................ 43 3.3.1 Apparatus .................................................................................. 45 3.4 Procedure................................................................................................ 46 3.4.1 Experimental Visual-Motor Task................................................ 47 3.5 Variables & Data Handling ...................................................................... 48 3.6 Data Analyses ......................................................................................... 49 3.6.1 Description of Participants ......................................................... 51 3.6.2 Visual-Motor Task Performance: Modulating Variables ............. 51 3.6.3 Visual-Motor Skill Acquisition: Modulating Variables ................. 53 3.6.4 Visual-Motor Skill Acquisition: Patterns of Change.................... 56 4 Results ........................................................................................................... 59 4.1 Description of Participants....................................................................... 60 4.2 Visual-Motor Task Performance: Modulating Variables .......................... 61 4.2.1 The Effect of Task Difficulty on Initial Visual-Motor Task Performance in TD Children ............................................................... 61 4.2.2 The Effect of Motor Ability on Initial Visual-Motor Task Performance When Task Difficulty Is Also Considered ...................... 63 4.3 Visual-Motor Skill Acquisition: Modulating Variables ............................... 66 4.3.1 The Effect of Repeated Trials on Visual-Motor Task Performance in TD Children When Task Difficulty Is Also Considered .................... 66 vi 4.3.2 The Effect of Motor Ability on Visual-Motor Task Performance When Repeated Trials and Task Difficulty Are Also Considered ........ 68 4.4 Visual-Motor Skill Acquisition: Patterns of Change ................................. 69 4.4.1 Rates of Visual-Motor Skill Acquisition ...................................... 70 4.4.2 Patterns of Change in Visual-Motor Task Performance over Repeated Trials .................................................................................. 74 5 Discussion ..................................................................................................... 83 5.1 Visual-Motor Task Performance: Modulating Variables ........................... 83 5.1.1 Describing the Effect of Task Difficulty on Initial Visual-Motor Task Performance in TD Children ...................................................... 83 5.1.2 Describing the Effect of Motor Ability on Initial Visual-Motor Performance When Task Difficulty Is Considered .............................. 85 5.2 Visual-Motor Skill Acquisition: Modulating Variables ............................... 87 5.2.1 Describing the Effect of Repeated Trials on Visual-Motor Task Performance in TD Children ............................................................... 88 5.2.2 Describing the Effect of Motor Ability on Visual-Motor Task Performance over Repeated Trials..................................................... 88 5.3 Visual-Motor Skill Acquisition: Patterns of Change ................................. 91 5.3.1 Patterns of Change in TD Children ............................................ 91 5.3.2 The Effect of Motor Ability on Patterns of Change..................... 92 5.4 Characterizing Visual-Motor Skill Acquisition and Task Performance in Children with DCD ......................................................................................... 95 5.4.1 Children with DCD Are Less Accurate Than Their Peers .......... 95 5.4.2 Children with DCD Are Slower, Faster, “Same as” Their Peers 97 5.5 Limitations ............................................................................................... 98 vii 5.5.1 Exploratory Nature of This Study ............................................... 98 5.5.2 Measuring Motor Ability ............................................................. 99 5.5.3 Technical Issues and Missing Data ......................................... 100 5.6 Clinical Implications and Future Directions............................................ 100 5.6.1 A Consideration for Identifying Children with DCD .................. 100 5.6.2 A Consideration for Intervening with Children with DCD ......... 101 5.6.3 A Consideration for Future Research to Characterize Visual- Motor Performance in DCD .............................................................. 101 5.7 Conclusions........................................................................................... 102 References ............................................................................................................ 104 Appendices ............................................................................................................ 114 viii LIST OF TABLES Table 3-1 Criteria used to describe participants as DCD or TD ............................... 39 Table 3-2 Independent variables investigated for their effect on visual-motor task performance ............................................................................................................ 49 Table 4-1 Description of Participants (N = 24) ......................................................... 60 Table 4-2 Investigating the effect of task difficulty on initial visual-motor task performance TD (n = 12) ......................................................................................... 61 Table 4-3 Investigating the effect of motor ability on initial visual-motor performance when task difficulty is considered in all children (N = 24). ........................................ 63 Table 4-4 Investigating the effect of task difficulty on visual-motor task performance over repeated trials in TD Children (n = 12). ............................................................ 67 Table 4-5 Investigating the effect of motor ability on visual-motor performance over repeated trials when task difficulty is taken into account (N = 24). .......................... 69 ix LIST OF FIGURES Figure 2-1 Relationship between task difficulty and expected performance as a function of the individual's skill level. ....................................................................... 26 Figure 3-1 Computer game and novel cursor controller........................................... 43 Figure 4-1 Mean initial movement times and distances travelled for each level of difficulty to illustrate the modulating effect of task difficulty on initial visual-motor task performance for TD (n=12). ..................................................................................... 62 Figure 4-2 Illustrating the modulating effect of motor ability on initial visual-motor performance for the simple, intermediate and complex tasks in all children (N = 24) ................................................................................................................................. 64 Figure 4-3 Illustrating the effect of motor ability on initial visual-motor task performance in all children (N = 24) when task difficulty is considered. ................... 65 Figure 4-4 Illustrating the effect of motor ability on initial visual-motor task performance in TD children (n = 12) when task difficulty is considered. .................. 67 Figure 4-5 Illustrating rates of skill acquisition and changes in visual-motor task performance over repeated trials during the complex task for TD children (n = 12). 70 Figure 4-6 Illustrating rates of skill acquisition and changes in visual-motor task performance over repeated trials during the simple task for all children (N = 24). ... 71 Figure 4-7 Illustrating changes in movement time over repeated trials .................... 72 Figure 4-8 Illustrating changes in visual-motor task performance over repeated trials during the complex task for all children and comparing predicted visual-motor task performance between TD children (n = 12) and all children (N = 24). ..................... 73 Figure 4-9 Illustrating patterns of change in visual-motor performance during complex task TD children (n = 12) ........................................................................... 75 x