Key findings from user studies
In addition to simulation experiments, we conducted user studies to test the effectiveness of SpeakFaster. The studies involved both non-AAC and ALS eye-gaze users, because participating in such studies can tax the already-limited time and energy of individuals with ALS that communicate with eye-gaze alone. The 19 non-AAC participants, typing on a mobile device by hand, gave us helpful information about the ease of use of the system and allowed us to quantitatively validate gains in keystroke rates, supporting our results from two individuals with ALS who exclusively use eye-gaze typing to communicate.
The study itself has two phases, a scripted and an unscripted phase. In the scripted phase the participants play the role of one of the people in a two-person conversation, where the content that the participant needs to type shows up on screen as text. In the unscripted phase the participant engages in 5- or 6-turn short dialogues with the experimenter where just the conversation opener is predetermined, e.g., “What kind of music do you listen to?” and the rest is spontaneous. Prior to the study, participants watched a video demo and got a small practice session of five conversations to familiarize themselves with the interface.
To assess the SpeakFaster interface, we measured motor action savings (keystrokes saved compared to the full set of characters to be typed), practicality (typing speed in words per minute), and learnability of the SpeakFaster UI (how much practice it takes for people to get comfortable using the system).
Across all studies, SpeakFaster demonstrated substantial keystroke savings compared to traditional baselines for both eye-gaze users and non-AAC participants with both scripted and unscripted dialogs. For non-AAC users, SpeakFaster allows for 56% (p = 8.0×10-11) keystrokes savings in the scripted scenario and 45% (p = 5.5×10−7) savings rate in the unscripted scenario. SpeakFaster also enabled significant keystroke savings in the scripted phase for our ALS eye-gaze tester.