Gaze Typing using Multi-key Selection Technique
Tanya Bafna · 2018 · Proceedings of the 20th International ACM SIGACCESS Conference on Computers and Accessibility (ASSETS '18) · doi:10.1145/3234695.3240992
Summary
This student research competition paper presents a multi-key selection technique for gaze typing that significantly speeds up text input for people with extreme motor disabilities such as full body paralysis. Traditional gaze typing uses dwell time — the user must fixate on each letter of a word for a fixed duration (typically 300-1000ms) to select it, resulting in maximum speeds of only 19.9 words per minute (wpm) for trained non-disabled users, far below speaking (150 wpm) or physical keyboard typing (40 wpm). The proposed technique combines dwell time and dwell-free approaches: the user fixates with full dwell time only on the first and last letters of a word, while simply gazing through the intermediate letters in sequence without dwelling. A disambiguation algorithm then uses the reliably selected first and last letters plus any detected intermediate letters to match against dictionary entries using a longest common subsequence algorithm, presenting the best match and suggestions. The technique was implemented using OptiKey, an open-source gaze-operated keyboard, with a Tobii Eye Tracker 4C.
Key findings
A preliminary study with 29 participants at a Health and Rehab Scandinavia fair (including three wheelchair users) showed that multi-key selection achieved an average typing speed of 7.5 wpm compared to 4.6 wpm for dwell time typing — a 63% improvement that was statistically significant (U=31, p<0.001). Critically, the error rate did not differ significantly between the two techniques. The mean error rate across both methods was 36.4% (with high variance), computed as modified Levenshtein distance. Subjective ratings showed the task was challenging (some rated multi-key selection 9/10 difficulty) but fun (all participants scored 5+ out of 10) and reasonably comfortable (79% scored 5+). An age effect was observed: participants under 30 typed faster with both methods, though this was not specifically attributable to familiarity with swipe-style input on touchscreens. The author notes this was a preliminary study with a modest sample size and that further controlled experiments with larger samples are needed, including comparison with dwell-free techniques like Dasher.
Relevance
This paper addresses a critical quality-of-life issue: gaze typing is often the only text input method available to people with conditions like locked-in syndrome or severe ALS, yet its slowness can be discouraging enough to reduce daily communication. A 63% speed improvement without increased errors could meaningfully impact the willingness of users to engage in extended communication, maintain employment, and stay connected via the internet. The multi-key selection concept — dwelling only on word boundaries while glancing through interior letters — is conceptually elegant, drawing an implicit analogy to swipe typing on touchscreens where users trace through letters without lifting their finger. For practitioners working on AAC and alternative input, this work demonstrates that significant speed gains may be achievable through interaction technique innovation rather than just hardware improvements, and that combining dwell and dwell-free approaches can balance accuracy (from dwell on key letters) with speed (from skipping dwell on interior letters).
Tags: eye tracking · gaze interaction · text entry · motor disability · paralysis · dwell click · alternative input · communication · locked-in syndrome