Efference copy and its limitations.

Efference copy, an internal brain signal informing the visual system of commands to move the eye, was the dominant explanation for visual space constancy for over a century. The explanation is not viable, however; the signal is to small, to slow, and too unreliable to support the perception of perfect constancy. Newer theories recognize that detailed image information does not survive refixation in any case. Efference copy is a viable explanation of static position perception and sensorimotor interaction, but the rich, stable visual world is an illusion.