D_O_IC_R_E_D#schizophrenia
New research indicates that hearing voices in schizophrenia may occur because the brain fails to recognize its own internal speech as its own
A team of psychologists from UNSW Sydney (University of New South Wales, Sydney, Australia) found the strongest evidence yet that the voices heard in schizophrenia arise when the brain fails to identify the speech happening inside the head.
The study, published in the journal *Schizophrenia Bulletin*, suggests that this discovery could help find biological clues related to schizophrenia.
This is very important because currently there are no blood tests, CT scans, or laboratory tests that specifically identify the disease (there are no clear physical markers that show if someone has schizophrenia).
Professor Thomas Whitford, from the UNSW School of Psychology, has been studying for years how inner speech affects thinking in healthy people and those with schizophrenia spectrum disorders.
“Inner speech is that voice in your head that silently narrates what you’re thinking – what you’re doing, planning, or noticing,” he explains.
“Most people have inner speech all the time, often without realizing it.
But some people never feel it.
“Our research shows that when we speak – even just in our minds – the part of the brain that processes sounds from the outside world becomes less active.
This happens because the brain anticipates the sound of our own voice.” But, in those who hear voices, this prediction goes wrong, and the brain acts as if the voice came from another person.
Brain Wave Analysis
Professor Whitford says this confirms what mental health experts have long suspected: auditory hallucinations in schizophrenia may be the person’s inner speech being mistaken for an external voice.
“This idea has been around for 50 years, but it was difficult to test because inner speech is something private,” he says.#Y#
“How do you measure this? One way is using EEG, a device that records the brain’s electrical activity.
Even without hearing the inner speech, the brain reacts to it.
In healthy people, using inner speech causes the same reduction in brain activity as speaking aloud.
“But, in those who hear voices, this reduction doesn’t happen.
In fact, the brain reacts even more strongly to inner speech, as if it came from outside.
This may explain why the voices seem so real.”
Sound Choices
Researchers divided people into three groups.
The first group consisted of 55 people with schizophrenia spectrum disorders who had heard voices (called auditory verbal hallucinations, or AVAs) in the past week.
The second group consisted of 44 people with schizophrenia who had never experienced AVAs or had not experienced them recently.
The third was a control group of 43 healthy people with no history of schizophrenia.
Each participant wore an EEG device to measure brain waves while listening to sounds through headphones.
They had to imagine saying “bah” or “bih” in their mind at the exact moment they heard one of these sounds in the headphones.
No one knew if the sound heard would match what they imagined.
In healthy people, when the sound from the headphones matched the imagined syllable, the EEG showed less activity in the auditory cortex – the area of “”the brain that processes sounds and speech.
This means that the brain anticipated the sound and somewhat “switched off” the reaction, as happens when we speak aloud.
But, in the group that had recently heard voices, the result was the opposite.
Instead of reducing activity, the EEG showed a stronger reaction when the imagined speech matched the sound heard.
“Their brains reacted more to the internal speech that matched the external sound – the opposite of what we saw in healthy people,” says Professor Whitford.
“This reversal of the normal suppression effect suggests that the brain’s prediction mechanism is broken in those who are currently having auditory hallucinations.
This may cause the internal voice to be confused with an external voice.”
The people in the second group – with schizophrenia, but without recent or no AVA – showed an intermediate pattern, between that of the healthy individuals and those who heard voices.
What Does This Mean”
Researchers say this is the strongest confirmation yet that the brains of people with schizophrenia confuse imagined speech with external speech.
“It’s always been a plausible theory – that people hear their own thoughts as if they were spoken aloud – but this new method has given the strongest and most direct test to date,” says Professor Whitford.
He says the next step is to see if this measurement can predict who will develop psychosis.
This would help identify people at high risk and allow for early interventions.
“This type of measurement has great potential to be a biological marker of the development of psychosis,” says the professor.
“Ultimately, understanding the biological causes of schizophrenia symptoms is the first essential step in creating new and effective treatments.”
Published in 10/29/2025 15h47
Text adapted by AI (Grok) and translated via Google API in the English version. Images from public image libraries or credits in the caption. Information about DOI, author and institution can be found in the body of the article.
Reference article:
Original study: