Enlarging a target primarily shortens correction, not the ballistic phase

What it is

Under the submovement model, increasing effective target width usually does not substantially alter the ballistic phase that brings a hand or pointer near the target. It expands acceptable endpoint range and chiefly reduces final pause, fine adjustment, and additional correction. Larger targets improve precise acquisition, not every part of movement equally.

Why it happens

The initial stroke is planned to cover most distance and is driven mainly by start position, distance, and movement onset. A broad target makes the ballistic endpoint more likely to fall within tolerance; even when it does not, relative residual error is smaller. Visual-feedback correction therefore needs fewer and smaller movements, concentrating total-time improvement after the stroke.

Studying it

Hold start and distance constant while varying effective width, separating initial and corrective phases through velocity peaks and pauses. Compare phase time, correction count, endpoint distribution, and error. Total time alone cannot tell whether width changed initiation strategy or endpoint control.

Where it stops holding

Very large targets can change strategy, prompting earlier action or a different gesture; moving targets, finger occlusion, and snapping also affect early motion. Phases are not always perfectly separable, so this is an average pattern. Target enlargement also has layout costs and should not be selected from motor benefit alone.

Related

• Same group: B1.16.1 Pointing usually comprises a fast ballistic stroke and slower corrections · B1.16.2 Correction count rises with relative ballistic endpoint error · B1.16.3 Proportional error reduction per correction yields a logarithmic time relation · B1.16.5 Without visual feedback, correction cannot occur and movement becomes ballistic
• Nearby: B1.01 Fitts's law · B1.11 Applicability and misuse of Fitts's law
• Search terms: submovement model · endpoint correction · target width