A decision tree depicting the IF-THEN rules for the selection of the grasp type and size. The inputs for the rules are the estimated lengths of the object's short (S) and long (L) axes. The lengths are compared against fixed thresholds (T) by following decision nodes (diamond shapes) of the tree until one of the leaf nodes (rounded rectangles) is reached. The thresholds are defined relative to the hand size and the size of the maximal aperture when the hand is preshaped according to a given grasp type. For example, T
= 90% PW, T
= 70% MLA, T
= 50% MPA, and T
= 65% MPA, where PW is the width of the palm (from lateral to medial side), while MPA and MLA are the maximal aperture sizes for the palmar and lateral grasps, respectively. For the full set of rules see the additional file 1.