EEG recordings from 157 participants revealed distinct neural patterns during inner speech preparation that accurately predict which schizophrenia patients experience auditory hallucinations. Healthy controls showed characteristic negative brain waves (contingent negative variation) when preparing to imagine speech sounds, but both hallucinating and non-hallucinating schizophrenia patients displayed abnormal positive waves instead, with hallucinating patients showing the most severe dysfunction. This neurophysiological evidence supports the corollary discharge theory—that auditory hallucinations arise when the brain fails to properly predict and monitor its own internal speech. The finding bridges motor control and perceptual prediction, suggesting that hallucinations stem from fundamental deficits in how the brain prepares for and monitors self-generated mental activity rather than purely auditory processing problems. While previous research focused on sensory aspects of hallucinations, this motor preparation angle offers new therapeutic targets. The ability to objectively measure hallucination risk through brain activity patterns could revolutionize early intervention strategies. However, the cross-sectional design limits causal interpretation, and replication across diverse patient populations remains necessary before clinical application.