It is fairly typical for individuals with profound hearing loss to experience other cognitive issues. There could be issues with memory or paying attention, for example. But are those other problems related to a lack of experience with language, or is there something else at play?
That is the very question Butler University Assistant Professor of Communication Sciences and Disorders Tonya Bergeson-Dana wanted to answer. Does hearing loss have an effect on other systems of development?
According to new research Bergeson-Dana co-authored in the journal PLOS One, the answer is yes.
“When one thinks about hearing loss, they think about hearing impairment, hearing aids, or maybe American Sign Language (ASL). No one thinks about the cascading effects on other systems as the child is developing,” she says. “What we are really seeing here is that hearing loss certainly has an effect on other systems in development, and not only that, but it starts very, very early, when the individual is an infant.”
Individuals who have hearing loss have other cognitive issues separate from their hearing impairment, she says. The assumption, though, she says, has largely been that those issues are related to a lack of experience with language.
The bigger question at play is if hearing loss is connected to the larger cognitive system, and therefore has a cascading effect on cognitive development. This is important, Bergeson-Dana says, because that would mean hearing loss has a direct effect on cognitive functions.
“What we are really looking at is whether congenital hearing loss has an effect on other systems in development,” she says. “We wanted to know how early this might start, and how impactful hearing loss is on the rest of the whole system.”
Forty-three infants, half of them hearing impaired and half of them hearing, aged seven-to-23 months, were presented with the same image over and over again. Once they acted like they were bored of the image, a new image appeared.
The purpose was to see how quickly the babies tired of the photos. Previous studies show that babies who get bored quickly have increases in cognitive functions. So, this was used as a measure to see if deafness slows cognitive development.
The rate of habituation, or how quickly a baby got bored with an image, was different between hearing babies and deaf babies. Babies with typical hearing were faster to habituate than babies with hearing loss. It took hearing impaired babies an average of eight-and-a-half trials before they got bored, compared to seven trials for hearing babies.
These findings, Bergeson-Dana says, can have major implications on how hearing loss is treated.
“We definitely should be treating hearing impairments much earlier than we do because of these clear cascading effects,” she says. “But more than that, we also need to provide children with cognitive skill interventions, in addition to just treating their hearing impairment.
“Before, we have just focused on their hearing impairment, but this study shows we have to think about the baby as a whole child, not just as a child with a hearing loss. The ear is connected to the brain.”