A short pinch is a click on whatever is currently pointed at

What it is

A pinch whose hold is zero or shorter than the drag threshold means click the currently pointed-at target. A ray, head pose, gaze, or a pointing finger decides “which one”; the short pinch decides “that one.” It carries no direction and paints no path in the air. Treating a short pinch as another wave sends people after amplitude and direction this hit does not have. Unlike a touchscreen tap, the landing is not where the finger is. It is on the object the pointing apparatus currently owns. The hand may rest at the hip and still click a button in the middle of the display.

Why it happens

Selection splits into aim and fire. A short pinch is only fire. Aim may come from head, eye, the other hand, or an extended finger on the same hand; the pinch does not care where aim came from, only the edge. Click errors therefore come in two kinds: aim error (wrong object) and edge error (missed pinch, or pinch that became a drag). Do not merge them into one “inaccurate click.” With no surface pinning the finger on the target, aim noise freezes at the firing instant: a shake sweeps the ray onto a neighbour on the pinch frame, and the neighbour is what got clicked. If the short-pinch threshold sits too close to the hold threshold that enters drag, people who meant to click drag instead, and the object walks away. Waves and palm-flips must not be interpreted as this hit; they are not a pulse on the current target.

Studying it

Use a multi-target selection task. Target size, spacing, and aiming channel (head / eye / hand) as factors; short pinch as the only fire. Measures: wrong object, missed click, and count of intended clicks that became drags. Log aim jitter at the firing instant to explain some neighbour hits. Control with a controller trigger or a touchscreen to separate channel error from pinch-edge error. Include trials where people meant to click but held a little long, or the threshold clash will not be measured.

Where it stops holding

A system with no pointing apparatus cannot use short pinch to select an object. At most it is a global toggle (pause, back), not a click on a target. When targets are smaller than aim noise, a shorter pinch will not save you; enlarge the target or change the aiming channel. Gaze-aim plus short pinch is a common pair, but gaze calibration drift will be blamed on the pinch. With two hands, say which hand's pinch counts as fire, or the other hand adjusting a collar becomes a click. The drag threshold must sit clearly above short pinch, or click semantics do not exist.

Applying it

• Document short pinch as “click the currently highlighted object,” and freeze aim at the pinch instant so the ray cannot sweep onto a neighbour around the edge.
• Separate short pinch from drag-entry in time, with different feedback: a pulse is a click; grab-and-move is a drag.
• Accept on dense targets and on deliberate “I meant to click but paused a beat.” Count neighbour misses and accidental drags separately.

Related

• Same group: C4.06.1 Fingertip contact gives a tactile endpoint · C4.06.2 Pinch splits into enter, hold, and release · C4.06.4 Recognition fails when fingertips are occluded or the hand faces away
• Adjacent: C1.07 Single and double click · C8.04 Gaze-plus-confirm combinations
• Search: pinch to select · air tap · clutch click