– Are you listening to me at all?
It is a question that discouraged parents often ask their distracted teenagers, and the true answer is probably “No”.
It’s hard to really blame them. New research on adolescents ’brains suggests that the reaction we have to certain voices naturally changes over time, making our mother’s voice feel less valuable.
When scanning the brains of children, those aged 12 and under showed an explosive neural response to the mother’s voice, activating reward centers and emotion processing centers in the brain.
Yet, sometime around a child’s 13th birthday, a change occurs.
The mother’s voice no longer causes the same neurological reaction. Instead, the brains of teenagers, regardless of gender, seem to respond more to all voices in general, whether they are new or remembered.
The changes are so obvious that researchers were able to guess a child’s age simply based on how their brain reacted to the mother’s voice.
“Just as an infant knows how to please his mother’s voice, an adolescent knows how to please new voices,” explains Stanford University psychiatrist Daniel Abrams.
“As a teenager, you don’t know you’re doing it. It’s just you: you have your friends and new friends and you want to spend time with them. Your mind is getting more sensitive and attracted to these unknown voices.”
Researchers suspect that this is a sign that the teenager’s brain is developing social skills. In other words, a teenager does not intentionally close his family; their brains are just maturing in a healthy way.
Numerous pieces of evidence show that a mother’s voice for young children plays an important role in their health and development, influencing their stress levels, their social connection, their feeding skills and their speech processing.
It is therefore logical that the child’s brain would be particularly attuned to the parent’s voice.
However, there comes a time when it is better to listen to people other than your mother.
“When teenagers seem to rebel because they don’t listen to their parents, it’s because they’re trained to pay more attention to voices outside their home,” says neuroscientist Vinod Menon, also of Stanford University.
The findings are based on fMRI results published by the same team of researchers in 2016, which found that children under the age of 12 show brain circuits selectively involved in the mother’s voice.
However, when the study expanded to 22 teenagers, aged between 13 and 16.5, the mother’s voice did not have exactly the same impact.
Instead, all the voices heard by teenagers activated neural circuits associated with auditory processing, selection of prominent information, and the formation of social memories.
When they were presented with a recording of their mother’s voice saying three nonsense, as opposed to a stranger’s voice saying the same thing, participants ’brain recordings actually showed less activation at reward centers in the brain.
The same was true for the ventromedial prefrontal cortex, which is the part of the brain that helps determine which social information is most valuable.
Researchers hope to investigate how these brain circuits differ among those with neurological conditions.
Among younger children, for example, Stanford researchers found that autism does not respond so strongly to a mother’s voice. Knowing more about the underlying neurobiological mechanisms could help us understand how social development occurs.
The findings of the current study are the first to suggest that as we age, our hearing is less focused on our mother and more on the voices of a range of people.
The idea is supported by other behavioral and neural studies, which also suggest that reward centers in adolescents ’brains are marked by increased sensitivity to news in general.
These changes could be key parts of healthy social development, enabling teenagers to better understand the perspectives and intentions of others.
“A child becomes independent at some point, and that has to be triggered by a fundamental biological signal,” Menon says.
“That’s what we discovered: this is a signal that helps teens get involved in the world and form relationships that allow them to be socially skilled outside of their families.”
The study was published in Journal of Neuroscience.