Shaping of Reach-to-Grasp Kinematics by Intentions: A Meta-Analysis

When we reach to grasp something, we need to take into account both the properties of the object we are grasping and the intention we have in mind. Previous research has found these constraints to be visible in the reach-to-grasp kinematics, but there is no consensus on which kinematic parameters are the most sensitive. To examine this, a systematic literature search and meta-analyses were performed. The search identified studies assessing how changes in either an object property or a prior intention affect reach-to-grasp kinematics in healthy participants. Hereafter, meta-analyses were conducted using a restricted maximum likelihood random effect model. The meta-analyses showed that changes in both object properties and prior intentions affected reach-to-grasp kinematics. Based on these results, the authors argue for a tripartition of the reach-to-grasp movement in which the accelerating part of the reach is primarily associated with transporting the hand to the object (i.e., extrinsic object properties), the decelerating part of the reach is used as a preparation for object manipulation (i.e., prepare the grasp or the subsequent action), and the grasp is associated with manipulating the object's intrinsic properties, especially object size.