Figure 1

The stability of the unimodal instantaneous speed profile in point to point hand movements and its susceptibility to changes in task context, decision making, and cognitive loads make the velocity dependent parameters a good candidate to amplify motor variability in deliberate vs. spontaneous control. (A) Velocity flows towards two alternative choices during a decision making task initiated from a similar position. Horizontal flows are from “change of mind” trajectories midway to the target. Black dots mark the place along the trajectories where the maximum velocity occurred. Speed profiles from the velocity flows are very variable and never in this task get unimodal. (B) the retractions of this task are also variable as the decision making process continues to unfold even after the decision was made (data from one graduate student out of 6 with similar performance presented at [23, 24]). (C) The hand trajectories of a child performing a pointing gesture to communicate his decision of a match to sample task. This is what natural pointing movements look like. (D) The evolution of the hand trajectories and decision making of that child captured and amplified in the speed profiles and the speed maxima (red profile is the forward segment of the black trajectory towards the target). Notice the regained stability of the hand speed which turns unimodal again within minutes.