A Three-Stage Model for the Acquisition of Anticipatory Planning Skills for Grip Selection during Object Manipulation in Young Children

When people manipulate objects, they plan their movements in advance of the execution in order to reach a desired goal or goal state at the end of the action. This can be nicely illustrated by the end-state comfort effect (ESC; Rosenbaum et al., 1990). For example, when people reach for an inverted cup, they will anticipate the final part of the manual rotation and are willing to adopt an initial awkward thumb-down grasp to end the rotation maneuver in a comfortable thumb-up posture (overturned-glass-task, OGT; Fischman, 1997). To this end, the grasping action is planned by selecting a particular final posture out of a set of stored postures (Rosenbaum et al., 2001). According to the " concept of order of planning " by Rosenbaum et al. (2012), such an anticipatory strategy is reminiscent of second-order planning, which entails not only planning for immediate task demands (as in first-order planning), but also considers what one wants to do with the object afterwards, such as holding the cup comfortable to pour tea into it. There is a large body of research documenting that the ESC effect is present in adults within a number of different motor tasks (see Rosenbaum et al., 2012, for a review), and even in different non-human primates (e.g., Weiss et al., 2007; Chapman et al., 2010). Therefore, it is somewhat surprising that young children do not show the ESC effect reliably (Weigelt and Schack, 2010; Jovanovic and Schwarzer, 2011). In fact, studies have identified a rather protracted developmental trajectory, with children reaching adult levels around the age of 10 and older (Thibaut and Toussaint, 2010; Stöckel et al., 2012; Scharoun and Bryden, 2014). While today there is much evidence on the development of the ESC effect in young children (for a review see Wunsch et al., 2013), so far, there is no theoretical model on how these motor planning skills are acquired. In the present paper, we attempt to provide a model to further the discussion on the development of the ESC effect. To this end, we outline a three-stage developmental model on the acquisition of anticipatory planning skills for grip selection in object manipulation (as signified by the ESC effect) across childhood. The general framing of the model and the separate skill acquisition stages in young children are primarily based on two different concepts to approach the control of complex human behavior: The Degrees of Freedom (DOF) …