Motor task

The novel motor task involved two-ball juggling using the right hand in a rolling-out pattern, with the balls being thrown in an arc to the right (clockwise when viewed from the participants’ perspective). These tasks were performed using bean bag balls, which are commonly used for juggling. A trial was considered complete if the participant stopped moving or dropped a ball. Each session comprised 10 trials; moreover, all but 2 participants performed 25 sessions, with one quitting at the 7th trial in the 21st session and the other at the 1st trial in the 22nd session. Two participants became proficient at juggling and extensively performed the task within single trials that they had to stop halfway through the session due to extreme fatigue.

Before commencing the sessions, the participants were asked to juggle two balls using their right hand across 10 trials without any instruction to confirm that no participants had practiced the motor task before the experiment. Subsequently, the participants watched an exemplar video (approximately 20 s) twice, followed by the first session. To mitigate the effects of fatigue, a 3-min break was taken at 10-session intervals. Additionally, each participant was allowed a 1-min break upon request.