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The Kilkenny Observer Friday 06 May 2022
kilkennyobserver.ie
Science & Wellbeing Sorry mammies, but your young teens have switched off and are no longer listening to ye! Teen brains no longer find their mothers’ voices uniquely rewarding starting around age 13, and start to tune into unfamiliar voices more, according to new research. For the study in the Journal of Neuroscience, the researchers used functional MRI brain scans to give the first detailed neurobiological explanation for how teens begin to separate from their parents. “Just as an infant knows to tune into her mother’s voice, an adolescent knows to tune into novel voices,” says lead author Daniel Abrams, clinical associate professor of psychiatry and behavioural sciences at Stanford University. “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, teens’ 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. However, 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 say. “A child becomes independent at some point, and that has to be precipitated by an underlying biological signal,” says 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
Why your teenager is not listening to you anymore form connections which allow them to be socially adept outside their families.” The team previously found that, in the brains of children 12 and under, hearing the mammy’s voice triggers an explosion of unique responses: A study published in 2016 showed that kids can identify their moms’ voices with extremely high accuracy and that the special sound of Mam cues not just the brain’s auditory-processing areas, but also many areas not triggered by unfamiliar voices, including reward centres, emotion-processing regions, visual processing centres, and brain networks that decide which incoming information is salient. “The mother’s voice is the sound source that teaches young kids all about the
social-emotional world and language development,” says Percy Mistry, co-lead author and a research scholar in psychiatry and behavioural sciences. “Foetuses 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 13 to 16.5 years of age. All participants had an IQ of at least 80 and were being raised by their biological mothers. They did not have any neurological, psychiatric, or learning disorders. The researchers recorded the teens’ 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 mom. Just like younger children, teens correctly identified their mothers’ voices more than 97% of the time. The researchers then placed the teens 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 teens’ age—in fact, the relationship was so strong researchers could use
the voice-response information in teens’ brain scans to predict how old they were. What distinguished teenagers from younger children was that unfamiliar voices elicited greater activity than Mother’s voice in the nucleus accumbens of the reward-processing system and in the ventromedial prefrontal cortex, a region involved in assigning value to social information. The switch toward unfamiliar voices happened in these brain centres between 13 and 14 years of age, and there was no difference between boys and girls. The research will help study what happens in the brains of adolescents with autism and other conditions that affect how they tune into voices and other social stimuli. Younger kids with autism don’t have as strong a brain response to their mothers’ voices as typically developing children, the researchers have found. The team is excited to have uncovered the foundations of teens’ ability to tune into new people, an important part of humans’ overall engagement with voices. The fact that the brain is so attuned to voices makes intuitive 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 say. “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 says. “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 says. “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.”
Sure, even the dogs on the street knew this Whether a dog’s breed is linked its behaviour is the study by dozens of scientists using a large citizen science database of dog genetics. They found only a paltry association, suggesting that breed has little influence on an individual dog’s behaviour. Environment, genetics, and upbringing play larger roles. The study’s findings call into question laws that target specific breeds as inherently dangerous, and other breedspecific rules. The new study, published in the journal Science, comes courtesy of a major effort by researchers associated with The Broad Institute at Harvard and MIT, the University of Massachusetts, and Arizona State University. Lead author Kathleen Morrill, a PhD student studying the genomics of behaviour in dogs, and her numerous co-researchers surveyed
owners of 18,385 purebred and mixed-breed dogs and genotyped 2,155 dogs as part
of the citizen science project Darwin’s Ark. For the project, participants
were given a battery of surveys to fill out about their dogs. They then received a DNA kit to swab their pup’s saliva and send it back to the lab for genetic testing. The information was collated into a large database that was freely shared with researchers around the world. In return, curious dog owners were sent a genetic and breed profile of their dogs. With the copious data provided to them by citizen scientists, Morrill and her team discerned a number of fascinating findings, but the biggest was this: “Breed offers little predictive value for individuals, explaining just 9% of variation in behaviour.” In other words, a breed is far more defined by how a dog looks, and has little to do with how an individual dog behaves. “Although breed may affect the likelihood of a particular behavior to occur,
breed alone is not, contrary to popular belief, informative enough to predict an individual’s disposition,” the authors wrote. The researchers broke down dog behaviour into eight categories: comfort level around humans, ease of stimulation or excitement, affinity toward toys, response to human training, how easily the dog is provoked by a frightening stimulus, comfort level around other dogs, engagement with the environment, and desire to be close to humans. Of these behavioural traits, response to human training (also known as biddability) and toy affinity were most linked with breed, but the associations were slight. Biddability was very common among Border Collies and Australian Shepherds, while toy affinity was common among Border Collies and
German Shepherds. A dog’s age was a much better predictor of behaviour. Older dogs, for example, were less excitable and less toy-driven than younger pups. Modern dog breeds really only go back about 160 years, “a blink in evolutionary history compared with the origin of dogs more than 10,000 years ago,” the researchers described. So it makes sense that breed wouldn’t explain a dog’s behaviour to a significant degree. Hunting through the thousands of canine genomes on file, the researchers found eleven genetic regions associated with various behaviours, ranging from howling frequency to human sociability. Genes in these regions varied widely within breeds, providing further evidence that breed is only marginally linked to behaviour.
