Uncovering the secrets of the ‘silent mind’

University of Auckland’s Dr Zoé Schelp has spent the past three years studying anauralia, the lack of a ‘mind’s ear’, and anendophasia, the absence of an ‘inner voice’.

“Anauralia and anendophasia are differences in how people think, rather than deficits or dysfunctions.

“They’re types of neurodiversity that many people have never heard of, so it feels important to understand them better and raise more awareness about them,” says Schelp.

Anauralia affects about one percent of the population. If a person with anauralia is asked to imagine hearing a sound, such as a bird singing or the chorus of a popular song, they can understand the concept, but don’t hear anything in their mind.

People with anendophasia can’t hear their own voice in their head.

“The two types of neurodivergence often occur together, but people can have one without the other,” says Schelp, who gained her PhD in the School of Psychology and Centre for Brain Research at the University of Auckland.

She surveyed 344 people with different levels of inner voice and mind’s ear to see if having a silent mind impacted on people’s lives.

Her study looked at whether people with silent minds have different levels of schizotypal traits.

Schizotypy is a personality dimension which can include odd beliefs, social anxiety, paranoia, magical thinking, and palpable sensations that things happened when they didn’t. People who experience moderate levels of schizotypy might be regarded as eccentric. However, those who experience abnormal extremes could be diagnosed with schizophrenia – a severe mental illness, which typically involves hearing voices and experiencing hallucinations, delusions, lack of motivation, and low mood.

Schelp’s recently published paper shows people with anauralia are less likely to experience vivid hallucinatory thoughts or magical beliefs. However, anauralics had significantly higher scores for social withdrawal and lack of joy in life.

“What we discovered about people with anauralia is completely new and came as a bit of a surprise,” she says.

People who strongly experienced an inner voice had normal levels of hallucinatory experiences, social participation and joy in life.

However, those who vividly heard imagined sounds had higher scores for certain schizotypy traits, including hallucinatory perceptions.

This suggests that people who have abnormal experiences of ‘hearing voices’ don’t necessarily have a loud inner voice, says Schelp.

“People seem to ‘hear voices’ when they vividly imagine sounds and wrongly perceive them as coming from the outside world.”

The research offers good news for people with silent minds, showing they are able to remember things and function just as well as those with noisier minds.

“Generally, people with anauralia or anendophasia don’t even know they have it, because they’ve lived with it their whole life.

“And of course, none of us really know what happens inside other people’s minds.”

Schelp says it’s important to raise awareness of anauralia and anendophasia, so people know if they have these differing experiences.

It could be beneficial for mental health professionals to be aware that some patients have silent minds, so they can help them appropriately, she says.

“Therapies that involve changing your inner narrative or imagining sounds might be less effective for people with a silent mind.

“If people can’t use their inner voice to give themselves affirming messages, they might be able to try a slightly different technique, like whispering aloud, for example.”

She says schizophrenia and related schizotypal personality disorders could look different in people with anauralia, given they are less likely to experience auditory hallucinations and are more likely to suffer from low mood.

“This could influence whether people with anauralia actually receive a schizophrenia diagnosis.”

Up until now, the silent mind has attracted little study. The term ‘anauralia’ was coined in 2021 by Schelp’s PhD supervisor, psychology professor Anthony Lambert, and former student Rish Hinwar.

Lambert developed the Auckland Auditory Imagery Scale, a tool Schelp used to measure people’s experiences of mind’s ear and inner voice.

Although Schelp doesn’t have a silent mind, as a violinist and music lover she was instantly fascinated by the idea some people couldn’t hear sounds or music in their heads.

She has since discovered people with silent minds can become musicians, but whether they can successfully compose music is a subject for future study.

Originally from Germany, Schelp completed her schooling early, before moving to New Zealand with her family to start university at the age of 15.

After winning a scholarship through the Marsden Fund of her supervisor, she graduated with a PhD on 22 September at the age of 25.

Looking to the future, she’s hoping to find funding so she can continue to explore the field of neuroscience, including schizophrenia, hallucinations, and different experiences of sound and silence inside the mind.