The graphic user interface (GUI) on the screen for the finger oscillation (FO) task (Figure 3A) contained two parallel lines, spaced 15mm apart, a black ball representing the user’s finger, and a set of crosshairs marking the starting point. While pointing at the GUI with their index finger over the sensor, participants were instructed to “tap” in the air as fast as possible so that the black ball on the screen moved below and then above the two parallel lines. They were to move only at the metacarpal-phalangeal joint, keeping their wrist and shoulder stationary. Each trial lasted 10s, with a 10-90s rest between trials. The assessment was complete when the subject performed 5 trials within 5 oscillations of each other. In the event that this requirement was not met, the number of taps in ten trials were averaged. The participant was given as many practice trials as desired. The test was performed with each hand.