Absent efference copy at the forward comparator, or absent any pre-action preparatory processes at the neurological level, however, the body-schematic system will fail to register a sense of agency
Gallagher argues that efference copy — the internal motor signal sent to a comparator — is a necessary condition for the body-schema to generate a sense of agency, and its absence directly produces the alienated self-experience characteristic of schizophrenia.
, How the Body Shapes the Mind, 2005thesis