Teenagers’ brains start tuning out their mother’s voice around the age of 13, study finds 

Ever get the feeling you’re talking to a brick wall when trying to communicate with your children?

Well, a new study suggests there may be some science to it, after finding that teenagers’ brains start tuning out their mothers’ voices around the age of 13.

This is because they no longer find it ‘uniquely rewarding’, researchers said, and instead tune into unfamiliar voices more.

The study by the Stanford School of Medicine used functional MRI brain scans to give the first detailed neurobiological explanation for how teenagers begin to separate from their parents.

It suggests that when your teenagers don’t seem to hear you, it’s not simply that they don’t want to clean their room or finish their homework — their brains aren’t registering your voice the way they did in pre-teenage years. 

‘Just as an infant knows to tune into her mother’s voice, an adolescent knows to tune into novel voices,’ said lead study author Daniel Abrams, clinical associate professor of psychiatry and behavioural sciences.

‘As a teen, you don’t know you’re doing this. You’re just being you: You’ve got your friends and new companions and you want to spend time with them. 

‘Your mind is increasingly sensitive to and attracted to these unfamiliar voices.’

In some ways, teenagers’ brains are more receptive to all voices — including their mothers’ — than the brains of children under 12, the researchers discovered, a finding that lines up with teenagers’ increased interest in many types of social signals.

But in teenage brains, the reward circuits and the brain centres that prioritise important stimuli are more activated by unfamiliar voices than by those of their mothers. 

The brain’s shift toward new voices is an aspect of healthy maturation, the researchers said.

‘A child becomes independent at some point, and that has to be precipitated by an underlying biological signal,’ said the study’s senior author Vinod Menon, a professor of psychiatry and behavioural sciences. 

‘That’s what we’ve uncovered: This is a signal that helps teens engage with the world and form connections which allow them to be socially adept outside their families.’

The Stanford team previously found that in the brains of children 12 and under, hearing a mother’s voice triggers an explosion of unique responses.

A study published in 2016 showed that children can identify their mother’s voice with extremely high accuracy, and that the special sound triggers not just the brain’s auditory-processing areas, but also many areas not triggered by unfamiliar voices.

This includes reward centres, emotion-processing regions, visual processing centres and brain networks that decide which incoming information is salient. 

The study by the Stanford School of Medicine used functional MRI brain scans to give the first detailed neurobiological explanation for how teenagers begin to separate from their parents

‘The mother’s voice is the sound source that teaches young kids all about the social-emotional world and language development,’ said Percy Mistry, co-lead author and a research scholar in psychiatry and behavioural sciences. 

‘Fetuses in utero can recognise their mother’s voice before they’re born, yet with adolescents — even though they’ve spent even more time with this sound source than babies have — their brains are tuning away from it in favour of voices they’ve never even heard.’

The new study built on the previous study, adding data from teenagers aged 13 to 16.5. 

The researchers recorded the teenagers’ mothers saying three nonsense words, which lasted just under a second. 

Using nonsense words ensured that the participants would not respond to the words’ meaning or emotional content.

Two women unfamiliar with the study subjects were recorded saying the same nonsense words. 

Each teenage participant listened to several repetitions of the nonsense-word recordings by their own mother and the unfamiliar women, presented in random order, and identified when they heard their mother.

Just like younger children, teenagers correctly identified their mothers’ voices more than 97 per cent of the time.

The teenagers were then placed in a magnetic resonance imaging scanner, where they listened again to the voice recordings. 

They also listened to brief recordings of household sounds, such as a dishwasher running, to allow the researchers to see how the brain responds to voices versus other non-social sounds.

The researchers found that, among teenagers, all voices elicited greater activation in several brain regions compared with younger children: the ‘voice-selective superior temporal sulcus’, an auditory processing area; ‘salience processing regions’ that filter which information is important; and the ‘posterior cingulate cortex’, which is involved in aspects of autobiographical and social memory. 

Brain responses to voices increased with teenagers’ age — in fact, the relationship was so strong researchers could use the voice-response information in adolescents’ brain scans to predict how old they were.

The fact that the brain is so attuned to voices makes sense — just ask anyone who has ever felt an emotional jolt at hearing a friend’s or family member’s voice after a long time, the researchers said.

‘The voices in our environment are this incredibly rewarding sound source that allow us to feel connected, included, part of a community and part of a family,’ Abrams said. 

‘Voices are really what connect us.’

Children’s social interactions undergo a major transformation during adolescence.

‘Our findings demonstrate that this process is rooted in neurobiological changes,’ Menon said. 

‘When teens appear to be rebelling by not listening to their parents, it is because they are wired to pay more attention to voices outside their home.’

The research has been published in the Journal of Neuroscience.