MEMORY PERFORMANCE AND ADAPTIVE STRATEGIES IN YOUNGER AND OLDER ADULTS DURING SINGLE AND DUAL TASK CONDITIONS VICTORIA GRACE COLLIN A thesis submitted in partial fulfilment of the requirements of the University of Greenwich for the Degree of Doctor of Philosophy June 2015 DECLARATION “I certify that this work has not been accepted in substance for any degree, and is not currently being submitted for any degree other than that of Doctor of Philosophy being studied at the University of Greenwich. I also declare that this work is the result of my own investigations except where otherwise identified by references and that I have not plagiarised the work of others.” Student Victoria G Collin Date First Supervisor Dr Sandhiran Patchay Date ii ACKNOWLEDGEMENTS . Firstly I would like to thank my supervisors, Dr Sandhi Patchay, Dr Trevor Thompson and Professor Pam Maras for all of your support and guidance over the years. It’s been a long and sometimes difficult journey, and I really appreciate all of your patience and understanding. I would also like to thank Dr Mitchell Longstaff who encouraged me to embark on this journey, and for all of his help early on as my supervisor. Thanks also to all my colleagues in the department for their advice and encouragement over the years. In particular I would like to thank Dr Claire Monks who was very helpful in her role as Programme Leader- sorry for all of the annoying questions! I would like to thank all of the participants, who offered their precious time to take part in my research. Without you this would not have been possible. My gratitude goes to John Johnstone, Sharon Staples, Pat and Jess who proved invaluable in helping to recruit older adults. My special thanks to Katie Rix and Claudia Roscini (the original knights!) who have provided such great company these last four years. I could not ask for better office mates. Thanks also to Jess, Sarah, Michelle, Karl, Amy, Jan and all the other PhD students who have provided a sympathetic ear and crucial peer support. Finally I would like to thank my family; Mum and Dad for always encouraging me to pursue my dreams (and providing much needed food parcels), Becky for her ability to always make me laugh, John for his way with words, Libby for her cuddles and Nan for her words of wisdom and cups of tea. Last but not least, thanks to Matt for putting up with me, believing in me, and for being an absolute wizard with excel/word. iii ABSTRACT Previous research has shown that the aging process is typically accompanied by a decline in a range of cognitive functions, including memory and attention. It has been hypothesised that older adults have reduced cognitive resources, which makes engaging in deeper encoding strategies difficult. However, training older adults in using encoding strategies has been shown to successfully improve their performance. Whether these benefits are apparent when performing more than one task at a time is less known. Owing to the demanding nature of dual tasks, older adults may be more penalised when using an effortful encoding strategy resulting in greater secondary task costs. Four studies were designed to determine whether encoding strategies (such as imagery/association) have the potential to enhance memory performance in young and older adults in single and dual task conditions. Participants were asked to encode a list of words on their own and also when undertaking a concurrent auditory discrimination task. Study 2 and 3 also examined age-differences in strategy selection and execution by ascertaining which strategies were adopted when participants were free to choose and when asked to use a specific strategy. Study 4 looked at whether the trained strategies could be transferred to an untrained working memory task. Overall the results revealed that training younger and older adults in encoding strategies can enhance memory performance in single and dual task conditions. However, this was not a consistent finding in all studies. Importantly older adults’ increase in performance in the dual tasks did not come at a cost to the secondary task. Results indicated that older and younger adults rely on different strategies to improve performance in single tasks, emphasising the importance to teach a variety of memory strategies and allowing participants to choose. The theoretical and practical implications of the findings are discussed. iv CONTENTS 1 Introduction ................................................................................................................. 1 1.1 Statement of Problem ............................................................................................... 5 1.2 Purpose of the research ............................................................................................. 5 2 Literature Review ........................................................................................................ 7 2.1 Chapter Overview ..................................................................................................... 7 2.2 Human Cognition...................................................................................................... 7 2.2.1 Memory ............................................................................................................ 7 2.2.1.1 The Perceptual Representational System (PRS) ........................................ 9 2.2.1.2 Primary Memory/ Short- Term/Working Memory .................................... 9 2.2.1.3 Long-term Memory .................................................................................. 12 2.2.1.4 Episodic memory...................................................................................... 13 2.2.1.5 Semantic memory ..................................................................................... 14 2.2.1.6 Procedural memory .................................................................................. 15 2.2.1.7 Summary .................................................................................................. 15 2.2.2 Attention ......................................................................................................... 16 2.2.2.1 Selective Attention ................................................................................... 16 2.2.2.2 Focused Attention .................................................................................... 17 2.2.2.3 Sustained Attention .................................................................................. 18 2.2.2.4 Divided Attention ..................................................................................... 18 2.2.2.5 Relationship between Memory & Attention ............................................ 22 2.2.2.6 Summary .................................................................................................. 24 2.3 Cognitive Aging in Healthy Older Adults .............................................................. 25 2.3.1 The Pattern of Decline ................................................................................... 25 2.3.2 Theories of Cognitive Aging .......................................................................... 27 2.3.2.1 Speed of Processing ................................................................................. 27 2.3.2.2 Working Memory/Attentional Resources ................................................ 29 2.3.2.3 Inhibition .................................................................................................. 31 2.3.2.4 Sensory Function ...................................................................................... 34 2.3.3 The Aging Brain ............................................................................................. 34 2.3.3.1 Evidence from Neuropsychology- Frontal Lobe Hypothesis ................... 35 2.3.4 Divided Attention & Aging ............................................................................ 37 2.3.5 Summary ........................................................................................................ 40 2.4 Improving Memory Performance ........................................................................... 41 2.4.1 Strategy use .................................................................................................... 41 2.4.2 Working Memory and Strategy Use .............................................................. 41 2.4.3 Aging and Strategy use .................................................................................. 44 2.4.4 Adaptivity in Strategy Use ............................................................................. 49 2.4.4.1 Adaptive Strategy in Older Adults ........................................................... 49 2.4.5 Summary ........................................................................................................ 52 2.5 Divided Attention and Strategy Use ....................................................................... 53 2.6 Current Research .................................................................................................... 54 3 Methodological Overview ......................................................................................... 57 3.1 Aims of study .......................................................................................................... 57 3.2 Rationale/Justification of Method........................................................................... 57 3.2.1 Cross sectional vs Longitudinal Design ......................................................... 58 3.2.2 Dual-task