Developing tasks of relational reasoning to asses the effects of cognitive ageing

This thesis investigates the effectiveness of five tasks designed to assess ability to process cognitive relations in a normally ageing population. The tasks are based on the theory of relational complexity, which defines cognitive processing capacity in terms of the complexity of relations that can be processed. The literature on working memory and processing capacity is examined, including the relationship between these constructs. The assessment of processing capacity adopted in the thesis differs from some previous approaches in the emphasis on processing of information while minimizing the storage element often found in tasks deemed to assess working memory capacity. A series of tasks have been developed for the purpose of assessing cognitive processing ability by systematically varying processing load as measured by relational complexity, or the number of variables which must be processed in a single decision. Each task contains a number of items at different levels of relational complexity. In essence, this project attempted to answer two main questions: 1. are relational complexity measures likely to be a useful way of assessing cognitive performance with age? 2. does the ability to process cognitive relations decline with age? Chapter One reviews literature pertaining to working memory, cognitive capacity, and task demand or processing load. The chapter considers the effectiveness of both short-term and working memory constructs in explaining the human ability to process information. The chapter considers the relative effectiveness of working memory span measure of cognitive processing capacity. The final section of this chapter approaches the idea of capacity limits from a different perspective. Moving away from human capacity limits, this section instead focuses on the manipulation of task demand or processing load. The concept of relational complexity is introduced as a potential means of manipulating the processing load of a task. Chapter two further explores the notion that both task load and the mental resources neuroimaging studies was considered. The second section of this chapter deals with the aging brain and working memory. Finally working memory was considered from the perspective of an influential theory of cognitive aging – the processing sp4ed theory. The roles played by both processing speed and working memory in complex cognitive tasks were considered. Chapters 3 and 4 reviewed the modification and development of two particular tasks, designed to vary in levels of relational complexity. Chapter 3 focused on the Categorical Syllogisms Task. Chapter 4 dealt with a modified version of the N-Back task. Chapters 5 to 7 outline the trial of a number of tasks designed to vary in levels of complexity or processing load with a normally aging population. Ninety older subjects (ranging from 54 to 84 years), and their younger subjects (ranging from 24 to 35 years) were individually tested on five “relational complexity” tasks and a range of commonly used neuropyshcological tasks. Prior to assessment all subjects were screened to ensure the existence of no neurological, psychiatric, or medical conditions that might impact on cognitive performance. Chapter 5 and 6, respectively, outline the method and results of the current study using a normal aging population. Chapter 7 discusses the theoretical and practical implications of the stud, and considers areas for future research. Overall, he result of this project confirm that four of the five relational complexity tasks under development showed promise as tools for assessing the ability to process relations . Recommendations for further development of these tasks are made. The study also confirmed that the ability to process cognitive relations does indeed decline with age. In particular, then, the results indicated that the tasks do show promise as measures of performance in the areas of cognitive aging