Effector independence in writing.

This study concerns motor representations acquired in learning to write. Most theorists assume that at the highest levels of the motor programming hierarchy, learned motor programs for writing characters (e.g., "A") are effector-independent, specifying the order and trajectories of writing strokes in a form not tied to specific effectors (e.g., right hand). On this view, once a high-level motor program has been learned with one effector, that same program will be used for writing with other effectors. However, in experiments conducted during 2018-2024, we found a clear qualitative difference between dominant and nondominant hands for participants writing in uppercase print: the direction of horizontal writing strokes (rightward or leftward) varied systematically with the hand used for writing. We interpret this phenomenon as evidence against the standard effector independence hypothesis and offer two alternatives. The first proposes that even the highest level motor programs are effector-specific. The second assumes that high-level motor programs learned with one effector can drive writing with other effectors, yet may be nonoptimal for a novel effector, in which case a new motor program may be generated. Both hypotheses imply a dual-route conception in which a high-level motor program may be activated either by retrieving a previously learned program from memory, or by generating a new program on the fly. (PsycInfo Database Record (c) 2025 APA, all rights reserved).