The “why” of reaching: Second-order planning across the adult lifespan.

Second-order planning, planning that takes into account imminent and subsequent task demands, has been shown to be essential during everyday movement. For example, the kinematics of a “reach to an object” action have been shown to be linked to the intended goal for the object (the prior intention). However, it is unclear whether this type of second-order planning for prior intention is preserved during aging or indeed how this differs across the adult lifespan. Kinematics of a reach action preceding four prior intentions–place in a “tight” hole, place in a “loose” hole, throw, or lift–were measured in 122 people aged 20—81 years. The kinematics of the reach movement demonstrated that all participants tailored their reach movement to the prior intention, with the deceleration period of the reach discriminating across groups. The 20s and 30s group showed a different deceleration period during the reach for tight versus loose place prior intentions; this was not seen after 39 years of age, and the 70 + group showed no discrimination across the deceleration period for the four prior intentions. When considering movement efficiency of the place actions, we found it could be predicted by age and that this relationship was mediated by discrimination across the deceleration period. This study demonstrates that a clear difference is seen in the way in which second-order planning is used across the lifespan and that this has implications for movement efficiency. (PsycINFO Database Record (c) 2019 APA, all rights reserved)