Efference Copy

An efference copy or efferent copy is an internal copy of an outflowing (efferent), movement-producing signal generated by the motor system. It can be collated with the (reafferent) sensory input that results from the agent's movement, enabling a comparison of actual movement with desired movement, and a shielding of perception from particular self-induced effects on the sensory input to achieve perceptual stability. Together with internal models, efference copies can serve to enable the brain to predict the effects of an action.

An equal term with a different history is corollary discharge.

Efference copies are important in enabling motor adaptation such as to enhance gaze stability. They have a role in the perception of self and nonself electric fields in electric fish. They also underlie the phenomenon of tickling.