Inner speech and the body error theory

Inner speech is commonly understood as the conscious experience of a voice within the mind. A recurrent theme is that it involves a representation of overt speech (e.g., phonetic properties) arising from a copy of speech instructions that were suppressed. The Body Error Theory (BET) proposes a broader picture: inner speech is a cross-modal illusion mixing interoception and audition. Slight, well-confirmed activities in the speech musculature during inner speech help transform representations of normal but quiet nonverbal sounds (e.g., breathing, background noise) into a mistaken perception of inner speech. In short, activities in the speech musculature mix with sounds to create the appearance of speech sounds, explaining the "voice within the mind." BET is shown to fit standard information-processing accounts of speech monitoring, to accommodate central insights of leading theories, to be supported by experience-sampling data, and to be empirically testable against rivals.