False triggers of blink input are easily confused with fatigue and dryness

What it is

False positives in blink input are unusually hard because they are often not noise but actions the body is demanding: the cornea is dry and must blink, the lids are tired and must close, allergy makes them squeeze. Treating those as commands punishes people for taking care of their eyes. False trigger and physiological need share one motion, unlike a mistaken key, which you can take your hand off.

Why it happens

The blink after tear-film breakup is protective; duration and force can both exceed ordinary spontaneous blinks and land in the “long closure = command” band. Air-conditioning, contact lenses, and long near-screen work raise the rate and duration of those protective blinks. Fatigue slows blinks and makes them incomplete; a detector may split one unfinished fatigue blink into two events, or count one long closure as a command. Allergic squeezing is even more irregular.

People cannot stop wetting the cornea to spare the UI. If a false trigger has no cheap undo, they enter a bind: tolerate dry eye, or keep undoing false commands. That differs from a false dwell—during dwell the eyes are still open and gaze can leave.

Studying it

Measure blink-command false positives at baseline, after two hours of forced near-screen work, in unventilated air-conditioning, and after artificial tears. Correlate with tear-breakup time if available, or with rated dryness. The session must be long enough: the first fifteen minutes the eyes are still wet. Contacts and frames separately. Do not claim low false positives on people who just had drops.

Where it stops holding

Wind, a pool, winter heating can raise false positives an order of magnitude above the lab; blink input should degrade or switch off. A system that never uses blink, only gaze plus a key, does not have this confusion. Conversely, assistive communication that uses blink as the only confirm must design undo for dry eye as daily, not as an edge. Some drugs (antihistamines, some psychiatric medications) reduce tears and turn “rare false trigger” into several per minute.

Applying it

• Pair blink commands with immediate, cheap undo, and raise the threshold or close the channel after dryness or a long session.
• On a burst of false triggers, ask whether the eyes are dry and offer to pause blink input, rather than keep executing.
• Verify by remeasuring false positives after at least an hour of screen time against session start; if they rise, the default policy must include raising the threshold or turning the channel off.

Related

• Same group: C8.11.1 Spontaneous physiological blinks and voluntary blinks must be distinguished · C8.11.2 Voluntary blink commands are usually recognized by lid-closure duration, not a single blink · C8.11.3 Using a wink as a command requires left/right discrimination and is infeasible for some users
• Adjacent: C8.03 Midas touch in eye input · C2.13 Touch in extreme conditions
• Search: dry eye · false trigger · blink fatigue