Understanding alternate physical interaction strategies to improve product design for older adults
Nasarwanji, Mahiyar Farrokh
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All individuals adopt some form of physical and cognitive coping. Coping behaviors are most frequently observed for individuals with limited ability and for challenging tasks. To reduce the stigma associated with the term coping the terms Common Interaction Strategies (CIS) and Alternate Interaction Strategies (AIS) were coined to represent frequently and infrequently used interaction strategies respectively. Designers often design for a limited set of interaction strategies and the use of AIS are not considered. In addition, predicting performance on tasks can be a challenge when individuals unexpectedly adopt AIS. Current models of person-product interaction such as the ability-demand model and the transactional model are inadequate to explain coping strategies. Hence, although there is an awareness of coping strategies there is a lack of theoretical understanding about how, when and why individual adopt coping strategies. To provide a more holistic view of interactions in an ecological perspective an Ecological Interaction Framework (EIF) was developed that includes the human, product and environment and describes the interactions between them. A multi-layered ability-demand approach was then developed to explain how, when and why individuals adopt AIS based on the EIF, contextual action theory and other literature. The underlying theory for the multi-layered ability-demand approach is that individuals have a diverse set strategies that they can use interchangeably. Individuals with lower ability are more likely to adopt a different strategy, from the available set of strategies, as compared to individuals with higher ability, to accommodate for a limitation in ability. Similarly, as product demand increases an individual is more likely to adopt a different strategy to accommodate for increased demand. To evaluate the model an experiment was conducted to study the effect of age (used as a surrogate measure of ability) and product demand on the interaction strategy adopted. Interaction with two products, a cabinet and a three-hole punch, representing a reaching and force application task respectively, were investigated. In addition, the influence of experience on strategies, the use of multiple attempts, changes in strategy, and task performance was evaluated. Findings indicated that postural interaction strategies were different for the two groups and these differences were driven by different biomechanical strategies adopted to accommodate for limitation in ability. In addition, as predicted by the model change in product demand led to a change in the interaction strategies to accommodate for the increased product demand. Although the basic elements of the model were supported, contrary to the model, specific interaction strategies varied widely and specific alternative interaction strategies could not be predicted. The developed model is the first step towards a clearer understating of the use of AIS. The findings of this dissertation will benefit the design of products and environments to make them more inclusive for individual with varying levels of ability.