AN EXAMINATION OF THREE THEORETICAL MODELS OF EXECUTIVE FUNCTIONING A DISSERTATION SUBMITTED IN PARTIAL FULFULLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSPHY IN THE GRADUATE SCHOOL OF THE TEXAS WOMAN’S UNIVERSITY DEPARTMENT OF PSYCHOLOGY AND PHILOSOPHY COLLEGE OF ARTS AND SCIENCES BY KAYLA M. DOWNING, B.S., M.T.S. DENTON, TEXAS ACKNOWLEDGMENTS First and foremost, I want to thank my parents, Vernon and Debbie Downing. Thank you for your unwavering love, support, and encouragement throughout this process. I would not be the person I am without your guidance and I will be eternally grateful for everything you have done for me. Next, I would like to thank my wonderful friends and fellow cohort members. This experience would not have been the same without you, and I cherish all of the times we shared both in laughter and in tears. Finally, I want to thank the psychology department faculty, and in particular Dr. Denise Maricle. Thank you for believing in me and for always being available for guidance and advice. Dr. Maricle - I appreciate all of your hard work and support throughout the dissertation process. I could not have done it without you. iii ABSTRACT KAYLA M. DOWNING AN EXAMINATION OF THREE THEORETICAL MODELS OF EXECUTIVE FUNCTIONING AUGUST 2015 The prominent focus on the study of executive functioning in the field of neuropsychology has yielded increased attention on the presentation of executive function and dysfunction in childhood (Hunter & Sparrow, 2012; McCloskey, Perkins, & Van Divner, 2009). The importance of executive skills in academic and social functioning has been demonstrated in brain and developmental research (Brock, Rimm-Kaufman, Nathanson, & Grimm, 2009; Shaul & Schwartz, 2014). Deficits in executive functioning have also been documented in many disorders found in childhood (Riccio, Sullivan, & Cohen, 2010). Researchers have created numerous theories and models to better understand executive functions. Continued disagreement exists in the field and no one theory or model has been accepted at this time; however, most researchers agree that executive functioning involves higher-order skills, which serve to monitor, control, and organize complex thoughts and behavior (Anderson, 2008). The purpose of this study was to compare three models of executive functions that represented common themes in the literature: a single-factor model, a model based upon the Integrated School Neuropsychology (SNP)/Cattell- Horn-Carroll (CHC) model, and a six-factor model proposed by the researcher. iv Participants in the this study were drawn from an archival data set of neuropsychological case studies previously obtained through the KIDS, Inc. School Neuropsychology Post-Graduate Certification Program. Structural equation modeling (SEM) using confirmatory factor analysis (CFA) was the statistical technique utilized to examine the three theoretical models. The factors were comprised of subtest scores from the four neuropsychological assessment batteries of the Woodcock-Johnson Tests of Cognitive Abilities, Third Edition Normative Update (WJ III COG NU), A Developmental Neuropsychological Assessment, Second Edition (NEPSY-II), the Test of Everyday Attention for Children (TEA-Ch), and the Delis-Kaplan Executive Function System (D-KEFS). Findings indicated that none of the original models tested successfully represented the construct of executive functioning as measured with a clinical sample of children. Theoretically sound modifications were then conducted to improve the models as measured by fit indices and standardized coefficients. The six-factor model proposed by the researcher demonstrated best fit of the three models after model modifications; however, a high degree of multicollinearity between factors continued to be observed for the both the Integrated SNP/CHC and six-factor model proposed by the researcher. The construct of cognitive flexibility was especially problematic for these models. Findings suggest that an even higher degree of overlap between executive skills may exist for children with disabilities compared to their typically developing peers. Future research is warranted to better understand how theoretical models of executive functioning present in children at different developmental periods or within similar disabilities. v Additional constructs, such as theory of mind, as well as alternative theories of executive functioning should be tested to explore whether another model may better represent the construct of executive functioning in a clinical population of children. This study provides additional insight into how executive functions present in children with disabilities, and contributes to a better understanding of how to appropriately provide assessment and intervention services for this population. vi TABLE OF CONTENTS Page ACKNOWLEDGMENTS .......................................................................................... iii ABSTRACT ................................................................................................................ iv LIST OF TABLES ....................................................................................................... x LIST OF FIGURES .................................................................................................. xiii Chapter I. INTRODUCTION ................................................................................................. 1 Brief Literature Review ................................................................................... 2 History......................................................................................................... 2 Prominent Theories ..................................................................................... 3 Neuroanatomy and Neurochemistry ........................................................... 5 Development ............................................................................................... 6 Genetic and Environmental Influences ....................................................... 7 Prevalence in Clinical Populations ............................................................. 8 Purpose, Rationale, and Significance of Study ................................................ 9 Research Question and Hypotheses .......................................................... 13 II. REVIEW OF THE LITERATURE ..................................................................... 15 Overview of Executive Functioning ............................................................... 15 History of Executive Functioning ................................................................... 16 1700s-1800s ............................................................................................... 16 1900-Present Day ....................................................................................... 18 Prominent Theories of Executive Function .................................................... 25 Unitary Theories ........................................................................................ 27 Multidimensional Theories ........................................................................ 28 Neuroanatomy ................................................................................................. 42 Structural Differences ................................................................................ 44 The Prefrontal Cortex (PFC) ...................................................................... 45 Neural Networks ........................................................................................ 46 Neuroanatomy and Clinical Disorders ....................................................... 50 vii Neurochemistry .......................................................................................... 51 Development of Executive Functions ............................................................. 56 Developmental Trends ............................................................................... 56 Genetics...................................................................................................... 64 Temperament ............................................................................................. 67 Environmental Differences ........................................................................ 68 Gender and Ethnic Differences ....................................................................... 78 Impact on Academic Success.......................................................................... 80 Relationship with IQ and Other Cognitive Factors......................................... 82 Dysfunction in Clinical Populations ............................................................... 84 Attention-Deficit/Hyperactivity Disorder (ADHD) ................................... 85 Autism Spectrum Disorder (ASD) ............................................................. 87 Learning Disability and Nonverbal Learning Disability (NVLD) ............. 89 Intellectual Disability (ID) ......................................................................... 91 Acquired Brain Injury ................................................................................ 91 Mood Disorders ......................................................................................... 95 Assessment of Executive Functioning ............................................................ 96 Behavioral Rating Scales ........................................................................... 98 Continuous Performance Tasks (CPTs)