A framework for estimating difficulty and exclusion from tasks of everyday living
Inclusive design research and practice seeks to make tasks of everyday living more accessible for everyone. Identifying Performance Shaping Factors (PSFs) and assessing their impact on performance is central to estimating difficulty and potential exclusion from everyday tasks. The analysis of human characteristics in this context is challenging because much of the existing capability data is fragmented and limited regarding how it can be validly used to predict exclusion.
This dissertation presents an exploratory framework for examining the extent to which task demands, age and capability PSFs impact performance and difficulty undertaking everyday tasks. This research involved a physical hand-based task demand-capability framework which is important because the hands are often a central feature for performing a broad range of everyday tasks.
An initial study involved developing a Hand Action Framework (HAF) to categorize hand actions used and explain performance using a proposed “strength x dexterity” capability approach. The task demands PSF was found to drive hand actions used across tasks and the level of Task Quality (TQ) achieved. That said, the impact of the Age PSF was not significant for these submaximal task demands. Study 2 included an evolving HAF which now incorporated a dimension of “user cost” which was decomposed into measures of task difficulty and task exertion which informed the analysis of difficulty associated with task performance. Task demand continued to drive hand actions used and although the PSF of age was not significant in shaping performance there was an emerging impact in this study for age on user cost with older participants reporting increased user cost difficulty handling heavier objects suggesting they were approaching the boundary of their performance capability. Increasing task demands (i.e., object weight) in a third study resulted in significant additional PSF impacts of age and capability on performance achieved and difficulty experienced with a disproportionately higher impact on older participants. Encouragingly, the Hand Action Framework (HAF) accounted for all hand actions used by all participants across a range of lifting and pouring tasks. A fourth study incorporated improvements including an increased number of people over 60 years and narrower age categories enabling a more robust analysis of older age. Six additional precision tasks were included to provide a broader range of everyday tasks. Results demonstrated the HAF captured a range of hand actions used with PSF of task demands, age and capability having a significant impact on hand actions used, performance achieved and user cost experienced. An important development involved an exploration of how Ergonomic Assessment Methods (EAMs) and Rehabilitation Assessment Methods (RAMs) could be applied from different contexts of use to explain performance achieved and difficulty experienced for the current research which provided a profound insight into how these EAMs and RAMs could be integrated into the assessment of performance and difficulty for everyday tasks context of use.