Touch Drift

The displacement of a finger's contact point on a touchscreen between the initial finger-down position and the final finger-up position during a single touch interaction. Touch drift measures how far a touch "slides" from where it started to where it ended, distinct from touch variability (which measures the total path traveled). Users with limited fine motor function, particularly those with tremor, spasm, or stiffness, tend to exhibit higher touch drift, meaning their finger moves significantly between landing on and lifting off the screen. Touch drift is problematic because most touch systems register the touch at either the finger-down or finger-up location — if these differ substantially, the system may activate the wrong target. Understanding touch drift can inform the design of more forgiving touch interfaces that account for movement during touch.