Characterizing "Motor Ability" for Ability-Based Design

Ability-based design (Wobbrock et al. 2011, 2018) offers conceptual guidance for its use in designing accessible systems, but the construct of “ability” itself—a crucial notion for ability-based design—is surprisingly elusive and absent from extant accounts. Different disciplines offer disparate notions regarding definitions and measures of “ability,” but ability-based design has yet to avail itself of these notions in its operationalization. To address this gap, this work reviews literature that quantifies motor abilities, provides guidance to distill metrics for human-computer interaction, and conceptualizes how motor ability should be quantified for ability-based design. We offer a three-dimensional framework composed of the user, context, and task, and we locate various metrics for ability to be used when implementing ability-based designs. We support this new conceptualization with example personas that occupy this three-dimensional space. This work can inform those using ability-based design to create systems that are responsive to users’ abilities.