When onset or offset fails, the gesture is swallowed or it fires twice
Aliases: missed onset · double fire · gesture repeat · dropped gesture
What it is
A bad slice does not show up as “92% recognition.” It shows up as two accidents. Swallowed: a complete action, zero system events, the person thinks they were not seen. Repeated: one action yields two results, or the end is missed and the next preparation is treated as a continuation. The classifier may have the class right and the accident still happens. In the field these are filed as “broken” and “too sensitive.” They are the same pair of edges.
Why it happens
Missed onset: speed never crossed the bar, the hand was at the edge of view, preparation was labelled noise, so the stroke finishes with no token. Missed offset: the hand jitters near the far point, the system thinks the command is still live, so one wave is split internally, or the return is taken as a second hit. Hair-trigger onset: adjusting a cuff is taken as start, and the following idle motion matches a command. Hair-trigger offset: a dip in speed mid-stroke commits, and the rest of the stroke commits again. Being swallowed makes people go larger or do it twice; going larger makes repeats more likely—a positive loop. This is not the model taking “wave” for “grab.” That is a class error. Here the class can be right and the count wrong.
Studying it
Align the event stream with intended tokens in a continuous log: one intent and zero events is a swallow; one intent and two or more events is a repeat. Do not fold repeats into “accuracy” as half-credit. Independent variables include edge cues, speed range, and whether reset is required. Run the same person before and after fatigue; droop changes the speed profile near offset. Playback should say whether onset missed, offset missed, or both fired early. A protocol that does one isolated token and has the experimenter call stop hides repeats.
Where it stops holding
Network or display delay inflates subjective “swallowed” reports: the event did fire, feedback arrived late, the person had already produced a second token, and the objective log now shows a repeat. Separate feedback delay from slice error. A one-item vocabulary of large moves tends to swallow more and repeat less; mirror pairs raise repeats. With several bodies in view, one person's offset can be taken as another's onset—an attribution problem wearing a segmentation mask. A brief tracking loss then recovery can emit a late event, experienced as “I already put my hand down and it turned the page anyway.”
Applying it
- Keep separate counters for swallowed and repeated. Set ship gates on each; do not merge them into one recognition rate.
- Commit feedback in the same instant as the event. Feedback slower than a person's retry turns a slice accident into a double hit.
- Accept on an uninterrupted ten-token sequence. Replay whether each intent maps one-to-one to an event. If people retry or one becomes two, fix the edges rather than collecting more shape samples.