Current Life Complexity and Its Relationship with Task-Switching Function in Young and Older Adults

Abstract

Globally, the proportion of people aged 60 and above is projected to increase from 14% in 2025 to 22% by 2050. Supporting the well-being of this growing older population requires a deeper understanding of cognitive functioning in later-life. The primary aim of the thesis was to gain further understanding of cognitive ageing by investigating the relationship between patterns of engagement in everyday activities and cognitive control in young and older adults. It was hypothesised that self-reported current life complexity and in-laboratory task-switching could be sensitive measures to detect decline under cognitive and behavioural compensation. Current life complexity was a novel concept proposed in this thesis, defined as the level of engagement in everyday activities during daily life that require individuals to invest cognitive resources. Task switching, the ability to alternate between tasks, was selected as an in-laboratory measure of cognitive control. Existing experimental studies showed that older adults were slower, and it was more effortful for them to switch between tasks, compared to young adults. To compensate for age-related changes, older adults tended to maintain accuracy by sacrificing speed of responding.

The most appropriate measure of current life complexity was sought through a conceptual literature review of pre-existing self-report instruments. This indicated no existing instrument was fit-for-purpose in assessing current life complexity. Consequently, a self-report Current Life Complexity Questionnaire (CLCQ) was developed by modifying an existing instrument, followed by evaluation through online-survey studies (Chapter Two; N = 384). The findings indicated there was adequate face validity for online participation, and meaningful scores could be extracted for assessing current life complexity.

The task-switching paradigms were selected by conducting a systematic review of task-switching in ageing (Chapter Three), which revealed substantial variability in task-switching paradigms and reporting of results. Two experimental studies, comparing two paradigms chosen on the basis of the systematic review, were undertaken in healthy young and older adults (Chapter Four). The first study (N = 44) involved a within-subject comparison of task-switching performance using a digit-based task-switching paradigm and a letter-based task-switching paradigm. The second study (N = 86) involved a between-subject comparison of task-switching performance with difficult-letter stimuli and easy-letter stimuli. Findings indicated that digit-based paradigms best captured reliable task-switching performance across age groups. Having established the CLCQ through online-survey studies, and identified an appropriate task-switching paradigm through the systematic review and experimental studies, a third experimental study (Chapter Four) examined the association between current life complexity and cognitive control as measured by the digit-based task-switching paradigm in young (N = 36) and older (N = 40) adults. The final experimental study found no significant association between current life complexity as measured by the CLCQ, and task-switching function (b = -3.73, t(34) = -1.18, p = 0.25 for young participants; b = -0.34, t(38) = -0.15, p = 0.88 for older participants).

This thesis included a systematic review, the proposal of the novel concept of current life complexity, and the development and initial validation of the CLCQ. This theoretical groundwork facilitated the investigation of the relationship between current life complexity and in-laboratory task-switching. While the hypothesised relationship was not supported, this work highlighted the importance of incorporating participant feedback in the development of self-report questionnaires and experimental procedures. These insights and measures provide a foundation for future research into patterns of engagement in everyday activities and cognitive control in ageing. Show more