External focus benefits depend on action-effect contingencies formed during motor skill training.

While the advantages of an external focus of attention are well-documented, recent empirical evidence has challenged its universal superiority. Adopting an effect-based framework, we propose that the efficacy of an external focus depends on learned associations between an action and its sensory consequences (i.e., action-effect contingencies). This study directly tested if limiting the development of these associations during practice diminishes the external focus advantage. Sixty-four participants practiced an underhand ball-tossing task over two days to a 16-ft target. A Full Feedback (FF) group trained with complete visual and auditory feedback of the ball's flight and landing, allowing for the development of action-effect relationships. A Limited Feedback (LF) group trained with occluded post-release visual and auditory feedback, limiting the formation of these associations. On the third day, both groups were tested on the trained target (16-ft) and a novel transfer target (20.5-ft) under external, internal, and control focus conditions. For the trained target, the FF group demonstrated superior accuracy, consistency, and reduced bias with an external focus, whereas the LF group showed no significant differences across focus conditions. Crucially, in the transfer test, the FF group maintained superior consistency with an external focus but exhibited significantly worse accuracy and bias compared to an internal focus. These findings support an effect-based account, suggesting that external focus benefits depend on established action-effect contingencies. Furthermore, the dissociation between consistency and accuracy during transfer suggests that while an external focus can prime a motor pattern (consistency), its ability to parameterize the action (accuracy) is constrained by the specific sensory information integrated during learning. We conclude by exploring the theoretical and practical ramifications of applying an effect-based framework to understanding the principles that govern an optimal focus of attention.