Working memory load does not affect sequential motor planning.

Movement planning disrupts the recall performance in a short term memory task, indicating that both processes share common working memory (WM) resources. In the current study, we tested whether this interference was bidirectional. To this end, we combined an easy or a difficult memory task (depleting different amounts of WM resources) with a sequential motor task (opening a column of drawers). The size of the hysteresis effect in the sequential motor task was measured as a proxy for the fraction of motor plan reuse. The different WM loads created by the memory task had no effect on the fractions of motor plan reuse and motor (re-)planning, which supports the idea that motor planning has priority access to WM. A recency effect (better recall of late items) was absent in a verbal memory task but present in a spatial one. Recency is commonly attributed to the episodic buffer, a non-domain-specific storage of the central executive. The domain-specific interference of the motor task with recency indicates that the second assumption needs to be reevaluated.