Received: 24 February 2017 | Accepted: 20 August 2017 DOI: 10.1002/dev.21573 RESEARCH ARTICLE The influence of grasping habits and object orientation on motor planning in children and adults Bianca Jovanovic | Gudrun Schwarzer Developmental Psychology, Justus-Liebig- University, Giessen, Germany Correspondence Bianca Jovanovic, Developmental Psychology, Justus-Liebig-University Giessen, FB 06, Otto- Behaghel-Str. 10/F1, 35394 Giessen, Germany. Email: bianca.jovanovic@psychol.uni- giessen.de Funding information Deutsche Forschungsgemeinschaft Collaborative Research Center, Grant number: SFB/TRR 135 Abstract We investigated the influence of habitual grasp strategies and object orientation on motor planning in 3-year-olds and 4- to 5-year-old children and adults. Participants were required to rotate different vertically oriented objects around 180°. Usually, adults perform this task by grasping objects with an awkward grip (thumb and index finger pointing downward) at the beginning of the movement, in order to finish it with a comfortable hand position. This pattern corresponds to the well-known end- state comfort effect (ESC) in grasp planning. The presented objects were associated with different habitual grasp orientations that either corresponded with the grasp direction required to reach end-state comfort (downward) or implied a contrary grasp orientation (upward). Additionally, they were presented either in their usual, canonical orientation (e.g., shovel with the blade oriented downward versus cup with its opening oriented upward) or upside down. As dependent variable we analyzed the number of grips conforming to the end-state comfort principle (ESC score) realized in each object type and orientation condition. The number of grips conforming to ESC strongly increased with age. In addition, the extent to which end-state comfort was considered was influenced by the actual orientation of the objects’ functional parts. Thus, in all age-groups the ESC score was highest when the functional parts of the objects were oriented downward (shovel presented canonically with blade pointing downward, cup presented upside down) and corresponded to the hand orientation needed to realize ESC. KEYWORDS affordances, development, end-state comfort, grasping, motor planning, object function, second-order planning 1 | INTRODUCTION The ability to plan goal-directed actions is a crucial skill for a successful and efficient interaction with our environment. By taking environ- mental constraints into account, we can optimize our movements and achieve our goals efficiently. Correspondingly, when we reach for an object in order to get hold of it, we usually prospectively adapt our hand orientation to the orientation of the goal object. The acquisition of corresponding aspects of “prospective control” (von Hofsten, 2004) is especially important against the background of a changing environment (Adolph & Robinson, 2015) and develops during the first year of life. As an example, while 5-month-old infants tend to adjust their hands to object size only after having made contact with an object, 7-month-olds adapt their hands before contact (Lockman, Ashmead, & Bushnell, 1984; McCarty, Clifton, Ashmead, Lee, & Goubet, 2001; Witherington, 2005). Similarly, infants are able to adapt Developmental Psychobiology. 2017;1–9. wileyonlinelibrary.com/journal/dev © 2017 Wiley Periodicals, Inc. | 1