Interaction Equivalency

Interaction Equivalency is an evaluation method for validating that alternative input and output modalities (voice, gesture, eye tracking, switch control) provide functionally equivalent access to system capabilities compared to standard input (keyboard, mouse). Developed by Shari Trewin, this method ensures that assistive and alternative interaction methods do not create barriers or diminish user capability. Rather than retrofitting accessibility as an afterthought, Interaction Equivalency assesses multi-modal design at design time, ensuring users with disabilities can access all functionality with comparable efficiency.