Figure 2. Decision tree for a structure-based gesture coding regime.

Starting from left, decisions for each gesture event are made regarding form and position of the different articulators, i.e., arm (elbow joint), hand (wrist joint) and fingers. After following each step to the right, codes are given to the single gesture forms, totaling 28 different gestures. For our analysis, we grouped the different gestures into two categories, the “bent arm gesture” (BG) and the “stretched arm gestures” (SG).