Motor equivalence in motor awareness.

Motor awareness (MA) describes the conscious access we have to the details of our movements. Although sensorimotor control relies on effector-specific transformations, many studies report similar MA thresholds across effectors, suggesting a shared, abstract representation. We tested this by having participants perform the same goal-directed reaching task once with a hand-held joystick and once by leaning with the whole body (center-of-mass displacement), using veridical or randomly deviated visual feedback. We measured corrective motor responses and fitted psychometric functions to derive MA thresholds. MA did not differ between effectors in non-deviated control trials or in "converging" trials where compensation aided the reach and thresholds correlated strongly between effectors. By contrast, in "diverging" trials with increased kinematic demand, MA relied more on effector-specific sensorimotor information. These findings support a largely effector-independent MA mechanism, consistent with motor-equivalence principles, that is flexibly reweighted toward effector-specific transformations under uncertainty, thereby linking low-level sensorimotor corrections with abstract motor representations and consolidating a gap in conceptual frameworks of the sense of agency.