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Experiment 2 Stability of the TOL4 problem set

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              Improving the Utility

            of the Tower of London,

     a Neuropsychological Test of Planning.




             Jennifer Rae Tunstall
BA (Hons), Grad Dip Social Science (Counselling)




          School of Applied Psychology
           Faculty of Health Sciences
               Griffith University


A thesis submitted in fulfilment of the requirements
      of the degree of Master of Philosophy.




                 December, 1999
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                    SOURCES STATEMENT



To the best of my knowledge, the work presented in this thesis is

entirely original, except where acknowledged in the text. None of the

material has been submitted, either in whole or part, for a degree in

any university. All raw data and analyses are available on request.



Jenny Tunstall
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                                       ABSTRACT


       The utility of a popular test of planning, the Tower of London (TOL), was

improved by addressing its limitations. The ceiling effect of the most commonly used

version was removed by modifying the materials to increase item difficulty. To improve

reliability, psychometric criteria were used to select the test items. An initial pool of 33

problems was administered to 65 children (M = 6.92 years, SD = 1.08) and 73 adults (M

= 43.62 years, SD = 19.96) to derive 11 items of graded difficulty and maximal item

discrimination. When these items were administered to 33 undergraduates (M = 26.10

years, SD = 9.79), the single item which did not retain its difficulty level was removed.

Although low, the internal consistency in this sample (split-half r = .39) was higher than

that of the TOL (Cronbach’s α = .30) which was administered to 23 undergraduates (M

= 25.61 years, SD = 8.69).

       Normative data for the modified version (the TOL4) were collected for a total of

447 people aged between 5 and 53 years. The split-half reliability in this sample was

acceptable (r = .60), as was the 1-month test-retest reliability of .71 for a sample of 61

adults and children (M = 26.08 years, SD = 13.98). Although there was a slight practice

effect, F(1,60) = 6.80, p = .01, the improvement was not clinically important (Mtime1 =

20.59, SD = 4.34; Mtime2 = 21.49, SD = 3.16).

       The construct validity of the total score as a measure of planning was

demonstrated in three ways. First, the developmental improvement in the normative

sample was consistent with both cognitive theory and previous research with the TOL.

Second, in a sample of 73 undergraduates (M = 24.77 years, SD = 8.39) the total score

correlated with measures of planning (Tinkertoy Test, r = .28, p < .05; Porteus Mazes; r

= -.27, p < .05), but not with measures of other abilities, such as concept formation,
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verbal fluency, switching and memory. Finally, in a principal components analysis with

the same sample, the total score loaded with a measure from the Porteus Mazes on a

Planning component. In contrast, the planning time measure had a different

developmental trajectory and different correlations. It appeared to measure response

inhibition and the speed of encoding and conceptualising problems.

       The results of this study have several implications for improving the assessment

of planning in both clinical and experimental contexts. Most important, users can be

confident that the TOL4 accurately measures aspects of planning ability, is suitable for

repeated administrations with the same client, and is applicable across a wide age range.

       Additional research to extend the norms to older adults and to evaluate criterion-

related validity would further improve the utility of the TOL4.
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                              ACKNOWLEDGEMENTS


       It was a privilege and a pleasure to be supervised by Dr David Shum and
Professor John O’Gorman. I am sincerely grateful for their generosity, both in
knowledge and spirit, and for their support during my incapacity. I especially thank Dr
Shum for his endless consideration of my circumstances and creative suggestions for
my benefit. This thesis owes much to his genuine interest and motivating influence.

       To Al Unwin, my friend and confidante, I am deeply indebted. Without his
unwavering succour, encouragement and compassion this thesis would not have been
possible.

        For their support and willingness to assist whenever the opportunity arose, I
thank my family and friends. Special thanks go to my mother, Phyllis Tunstall, for her
help and a lifetime of support. Also, in loving memory, I thank my father for fostering
the desire to be the best I could be.

         I am also obliged to all the people who gave freely of their precious time and
effort to enable me to contact participants. Of course, I am deeply indebted to the
children, adolescents and adults who provided the data for this project for their
enthusiastic participation and application.

       Finally, I thank Dr Trevor Hine for his assistance with colour information.
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                                              TABLE OF CONTENTS


List of Figures .................................................................................................................vii
List of Tables...................................................................................................................vii
List of Appendices .........................................................................................................viii
Introduction ....................................................................................................................... 1
   Introduction ...................................................................................................................2
   The Construct of Planning ............................................................................................ 4
   Neuroanatomical Basis of Planning ..............................................................................8
   Tasks Used to Investigate Planning ............................................................................10
   The Present Study........................................................................................................ 37
Experiment 1: Development of the problem set ............................................................. 39
   Introduction ................................................................................................................. 40
   Method ........................................................................................................................ 44
   Results & Discussion .................................................................................................. 47
Experiment 2: Administration of the reduced TOL4 problem set .................................. 54
   Introduction ................................................................................................................. 55
   Method ........................................................................................................................ 57
   Results and Discussion................................................................................................ 58
Experiment 3: Validity of the TOL4...............................................................................63
   Introduction ................................................................................................................. 65
   Method ........................................................................................................................ 93
   Results ....................................................................................................................... 105
   Discussion ................................................................................................................. 121
General Discussion........................................................................................................ 139
   Introduction ............................................................................................................... 140
   Constructs Measured by TOL4 Scores ..................................................................... 141
   Relationship of TOL4 Scores to the Models of Planning ......................................... 142
   Implications of the Findings...................................................................................... 144
   Limitations ................................................................................................................ 149
   Suggestions for Future Research............................................................................... 151
References ..................................................................................................................... 156
Appendices....................................................................................................................172
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                                              LIST OF FIGURES


Figure 1. A three-disc version of the Tower of Hanoi. ................................................. 12
Figure 2. Problem space for the 3-disc Tower of Hanoi. . ............................................ 13
Figure 3. Tower- and flat-endings for the TOH............................................................ 15
Figure 4. Norman and Shallice’s model of brain function............................................ 19
Figure 5. A comparison of selected models of higher cognitive functioning. .............. 20
Figure 6. The Tower of London (a 4-move problem)...................................................21
Figure 7. Shallice’s Tower of London compared with the modified version. ..............45
Figure 8. Greyscale picture of the TOL4. .....................................................................46
Figure 9. Difficulty of items in the TOL3.....................................................................59
Figure 10. Difficulty of items in the TOL4.....................................................................60
Figure 11. Cytoarchitectonic map of the cortex showing Brodmann’s areas.. ...............75
Figure 12. Difficulty of items in the final version of the TOL4. .................................. 106
Figure 13. TOL4 total scores as a function of age. ....................................................... 108
Figure 14. TOL4 average planning time as a function of age....................................... 111
Figure 15. Number of TOL4 problems solved on the first attempt
           as a function of age. ..................................................................................... 111
Figure 16. Number of TOL4 problems solved within three attempts
           as a function of age. ..................................................................................... 112
Figure 17. TOL4 average planning time for expanded age groupings. ........................115
Figure 18. TOL4 average planning time for simple and complex problems
           as a function of age. ..................................................................................... 115
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                                               LIST OF TABLES


Table 1 Item Analyses for the Adult Data .....................................................................49
Table 2 Item Analyses for the Children’s Data..............................................................50
Table 3 Corrected Item-Total Correlations for the 3- and 4-disc Towers of London....62
Table 4 Ages of Developmental Changes in Theories of Neurocognitive
        Development .....................................................................................................70
Table 5 Descriptions of the Samples in Each Analysis.................................................. 94
Table 6 Summary of Dunnett’s Test Comparing Wechsler Vocabulary Scale Scores
        of University Students with Other Age Groups ................................................ 96
Table 7 Summary Statistics for Age Group Comparisons on TOL4 Total Scores ...... 108
Table 8 Scale Scores for the TOL4 Total Scores......................................................... 110
Table 9 Correlations between TOL4 Measures ........................................................... 112
Table 10 Percentile Conversions for TOL4 Planning Time..........................................114
Table 11 Descriptive Statistics and Correlations of Tests with TOL4 Measures .........117
Table 12 Intercorrelations of Measures in the Principal Components
         Analysis (n = 51)............................................................................................119
Table 13 Component Loadings and Communalities (h2) for Principal Components
         Analysis with Orthogonal Rotation (n = 51)..................................................121
Table E1 Component Loadings and Communalities (h2) for Principal Components
         Analysis with Orthogonal Rotation (missing values estimated) .................... 180
Table E2 Intercorrelations between Measures in Principal Components
         Analysis (missing values estimated) ..............................................................182
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                                        LIST OF APPENDICES


Appendix A. Dimensions of the TOL4 .........................................................................172
Appendix B. TOL4 Instructions (After Krikorian et al., 1994) .................................... 173
Appendix C. Starting and Goal Configurations of TOL4 Problems............................. 177
Appendix D. TOL4 Record Form .................................................................................178
Appendix E. Principal Components Analysis with Estimated Data ............................. 179
Appendix F. Data for Experiment 1.............................................................................. 184
Appendix G. Data for Experiment 2 ............................................................................. 191
Appendix H. Data for Experiment 3 ............................................................................. 195

				
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Description: Experiment 2 Stability of the TOL4 problem set