According to researcher Thomas Whitford of the University of New South Wales, the idea has been known for fifty years but has been difficult to test because inner speech is so private and cannot be directly observed.
In this study, researchers used electroencephalography (EEG) to examine brain responses in three groups: 55 people with schizophrenia who had recent auditory hallucinations, 44 people with schizophrenia but without recent auditory hallucinations, and 43 people with no history of schizophrenia.
In this experiment, participants were asked to perform a simple yet precise task: listen to either the word "bah" or "bih" through headphones, while simultaneously internally saying one of the words in their minds. The strange thing about the experiment was that the participants didn't know in advance whether the word they were thinking of would match what they were hearing. When this alignment between the internal and external sounds occurred, a surprising response was observed: the brains of those with auditory hallucinations reacted abnormally strongly, while the response of healthy individuals was normal. This indicates that the brain in schizophrenia loses its ability to distinguish between internal and external sounds, treating internal thoughts as if they were real voices heard by others. This makes the experience of hearing voices seem realistic and frightening to the patient.
Whitford explains this phenomenon by saying that the brain normally anticipates our voice when we speak internally, reducing activity in the area responsible for hearing. However, in schizophrenia, this system is disrupted, and the brain fails to recognize the voice as internal and treats it as if it were coming from outside, making these voices seem very real to the patient.
This scientific discovery paves the way for predicting psychosis before its symptoms appear, allowing for early intervention and treatment at earlier stages.
The results were published in the journal Schizophrenia Bulletin.
