Car alarms and barking dogs, domestic spats and crying babies — the list of noise disturbances in poor urban areas seems endless, and it can leave lifelong neural damage on developing brains. Serious research into this area began nearly two decades ago, and now scientists are looking to bridge the gap between social understandings of poverty and the neuroscientific frameworks they shape.
A study out of Northwestern University draws upon the link between maternal education levels and income, and pivots the findings to better understand how maternal education affects neural processing of sound in the brain.
A study from 1995 sets the team’s foundation. Researchers Dr. Betty Hart and Dr. Todd Risley found that kids growing up in high-income households are typically exposed to 30 million more words than children growing up on welfare — by the time they’re 3 years old. The study has come to be a landmark in the field of childhood development, and one that has helped narrow future research into cognitive development across socioeconomic status.
The present study used the same principles to test a group of ninth-graders on their auditory abilities while they watched a subtitled movie of their choosing.
"These adolescents had noisier neural activity than their classmates, even when no sound was presented," Nina Kraus, professor of neurobiology at Northwestern and corresponding author of the study, said in a statement. “Think about the neural noise like static in a radio – with the announcer's voice coming in faintly.”
People can identify this type of sonic activity most obviously after a loud party or concert, when they’ve finally laid their head on their pillow but their ears continue to ring. This does not mean the study participants heard constant ringing, but their brains manifested the same behavior. Specifically, neural models “indicate that when the input to a neuron is noisier, the firing rate becomes more variable, ultimately limiting the amount of sensory information that can be transmitted."
These effects cropped up in subsequent tests of IQ, reading, and working memory, which produced poorer results compared to children whose mothers had more education. The researchers attributed these findings in part to prior studies that claim socioeconomic status is sensitive to intellectual performance. The solutions, they argue, may be as simple as modifying the way children interact with sound in the classroom.
"Modifying the auditory world for a particular student, even if just for a portion of the day,” said Erika Skoe, assistant professor of speech, language, and hearing sciences at the University of Connecticut, “may improve academic performance and fine-tune how sound is automatically encoded in the brain.”
For the child of meager means, this could mean a fairer shot at academic success simply through quieter learning environments and calmer settings — a refreshing break from the neural noise and cognitive chaos.
"If your brain is creating a different signal each time you hear a sound, you might be losing some of the details of the sound," Skoe added. "Losing these details may create challenges in the classroom and other noisy settings."
Scientists can use the present findings, the researchers posited, to further their understanding of how neural frameworks interact with, and get affected by, socioeconomic regions, in particular ones that produce different experiences and phenomena for the people who inhabit them.
"By studying socioeconomic status within a neuroscientific framework, we have the potential to expand our understanding of the biological signatures of poverty," Kraus concluded. "And a better understanding of how experiences shape the brain could inform educational efforts aimed at closing the socioeconomic achievement gap."