Deafness is the most common sensory problem for U.S. schoolchildren鈥攁nd one of the most long-studied鈥攜et researchers are only beginning to tease out the effects of sound versus language on deaf children鈥檚 learning growth.
In several new studies discussed at the American Association for the Advancement of Science here earlier this month, researchers examined the ways deafness interacts with other challenges, such as autism, and language and executive function problems.
鈥淩esearch on developmental disorders in signing children is of great importance both for practical reasons and scientific reasons,鈥� said Richard Meier, a linguistics and psychology professor at the University of Texas at Austin. 鈥淲e may be able to ask questions about typical and atypical developing children that we couldn鈥檛 ask if we only examined typically hearing children.鈥�
Studying deaf students can give researchers insights into other cognitive issues, such as autism spectrum disorders. In two prior studies (the first two sets of columns below), researchers found that students with autism spectrum disorders tended to use names when asked to identify a picture of themselves or the researcher, while typically developing students used the pronouns 鈥測ou鈥� or 鈥渕e.鈥� In 2015, researchers repeated the experiment with deaf students (the third pair of columns); those with autism also used names, even when they were complicated to finger-spell.
SOURCE: 鈥淧reliminary Findings of Similarities and Differences in the Signed and Spoken Language of Children With Autism,鈥� Aaron Shield
More than 1 in 500 children in the United States is born deaf or hard of hearing, making it the most common congential sensory problem in the country, according to estimates by the National Association for the Deaf, and those children have higher rates of certain other neurological issues, such as autism, than the general population. The National Academy of Pediatrics estimates that 98 percent of newborns receive a hearing test, but only about 1 in 4 with hearing loss are properly diagnosed and given services before they are 6 months old.
What happens in those six months? It depends, said Peter Hauser, a clinical neuropsychologist at the National Technical Institute for the Deaf at the Rochester Institute of Technology in New York.
Sound and Language
About 5 percent of deaf children are born to deaf parents who use sign language with them from birth in the same way that hearing parents speak to their children from their first hours. Those children, studies have found, typically hit the same language milestones as hearing children: babbling around 10 months, putting together their first words and sentences around 12 to 18 months, and starting to talk up a storm as 2-year-olds.
But 9 in 10 deaf babies are born to hearing parents, and it takes many hearing parents months or even years to sign fluently to their toddlers, if they do at all, Hauser and other researchers said during symposia at the meeting. In separate studies, Hauser and Matthew Hall, a linguistics researcher at the University of Connecticut, suggest a lack of early language could lead to long-term problems with attention and self control in children with hearing problems.
鈥淓xecutive function problems are not being driven by auditory deprivation but by language deprivation,鈥� Hall said. 鈥淏y far, the greatest risk for a deaf child鈥檚 cognitive development is language deprivation.鈥�
In a 2008 study of classroom observations, 10 kindergarten teachers of deaf children had to gesture twice as often to get the attention of children who had not been exposed to significant sign language before age 3 as to children who had been signing since birth, found symposium participant Jenny Singleton, psychology professor at Georgia Institute of Technology.
In another new study, Hauser asked deaf children and adults who had learned to sign before or after age 3 to perform a test of executive function, in which they connect numbered circles in patterns of different colors. Both children and adult early signers did the task 20 seconds faster, marking significantly better executive function.
Similarly, Hall discussed a 2014 study tracking deaf children who had been implanted with a cochlear implant鈥攁 device that translates sound into signals directly into the auditory nerve in the brain鈥攂etween ages 3 and 6. In a test of cognitive development and a survey of behavior problems related to attention and self control, those who had received a cochlear implant but no sign language did significantly worse than hearing children, but those who were deaf but fluent in American Sign Language performed on par with hearing children.
鈥楤ilingual Benefit?鈥�
In a separate analysis of reading-test performance, Hauser also found 鈥渂ilingual, bimodal鈥� adults鈥攖hose who were fluent in English and ASL and were exposed to signing since birth鈥攚ere faster than late-signing deaf adults or hearing adults at matching complex written sentences to corresponding pictures.
Both Hauser and Hall separately suggested that ASL may provide a cognitive 鈥渂ilingual benefit鈥� since it uses a different grammar than English, unlike systems that use English grammar in a signed rather than spoken mode.
鈥淚t has tremendous implications for parents and classrooms in the importance of early language and instruction,鈥� Hauser said.
That may prove controversial, as other researchers have argued that deaf children who receive cochlear implants should be given spoken interventions only. But a study out this month in the journal Pediatrics found that of more than 400 studies spanning 20 years of research comparing interventions for deaf children, only a handful actually compare the use of sign language with oral language for children whose hearing deficits began before age 3, and their quality varies considerably.
Sign language may also help educators and researchers understand other children who are not developing typically.
For example, autism researchers like Aaron Shield, a speech-language pathologist at Miami University of Ohio, have long debated why children with disorders in that spectrum often do not use pronouns. In prior studies, hearing children with autism tended to say specific names rather than using 鈥測ou鈥� or 鈥渕e,鈥� and some suggest it is because pronouns don鈥檛 have clear enough meanings. The meaning of 鈥渕e,鈥� for example, changes depending on the speaker.
ASL, by contrast, uses simple finger pointing to indicate 鈥測ou鈥� or 鈥渕e.鈥� If students with autism avoid using pronouns for clarity鈥檚 sake, Shield reasoned, deaf children with autism should have no problem using pronouns.
That鈥檚 not what he found, though, in a study of 23 children with autism who had been deaf and signing since birth. Even when they had to use longer or more complicated finger-spelling for names, deaf children with autism used specific names over pronouns, exactly as hearing children with autism did. Similarly, the deaf children with autism copied new signs exactly rather than mirroring them similar to hearing students with autism 鈥渆choing鈥� a speaker鈥檚 words rather than responding to them.
The findings from deaf children build on other evidence that language problems in autism may be related to perspective taking and other cognitive skills in language itself, rather than speech processing or articulation.
鈥淚t is not enough to have rich, full input into language to acquire it; you have to have the social skills to access it,鈥� Shield said.
