The day after Lydia Denworth’s son Alex was born, he failed a routine hearing test given to all newborns. Probably just mucus in the ears, the nurse explained. It turned out not to be. Thanks to a congenital malformation, Alex had too little hearing in both ears to hear language.
This was a crisis not just of the ears but of the brain itself, as Denworth explains in her book. A brain that has not had full exposure to language by age three is unlikely to learn language fluently and naturally, with lifelong consequences for the child.
Denworth threw herself into researching how hearing, language, and cochlear implants work in order to help her son. The result is “I Can Hear You Whisper: An Intimate Journey through the Science of Sound and Language” (Penguin, 2014).
As a science writer Denworth has written up what she learned, and the result is so comprehensive, wide-ranging, and well-written that it is essential reading for any parent of a child with hearing loss. Denworth has gone further into the scientific literature than any other writer I know of on this subject, including myself, and she interviewed a Who’s Who of people involved in developing cochlear implants. The result is a fascinating and magisterial book.
The narrative line of the book begins with her early suspicions that something was wrong. At age two, Alex’s scores for receptive and expressive language were in the eighth and sixth percentiles respectively. They tried hearing aids, but ultimately opted for a cochlear implant.
The implant worked. Denworth writes,
Now, after one year of using the cochlear implant, the change was almost unbelievable. His expressive language had risen to the sixty -third percentile and his receptive language to the eigthty-eighth percentile. He was actually above age level on some measures. And that was compared to hearing children. I stared at the Post-it note and then at the therapist. “Oh my god!” was all I could say. I picked Alex up and hugged him tight. “You did it,” I said. From the evaluation, we went straight to Clarke so Alex could go back to school. The director’s office was next door to his classroom. I knocked on the door frame and Teresa Boemio looked up from her desk. “How did it go?” she asked as soon as she saw me. She knew where we’d been.
“Pretty well.” I handed over the Post-it note. “Wow!” she cried. “WOW!”
To explain the remarkable success of cochlear implants, Denworth offers the most detailed history of them published in the popular press to date. There have been a number of excellent academic papers on the history of cochlear implants, including Mara Mills’s “Do Signals Have Politics? Inscribing Abilities in Cochlear Implants,” but no really good book-length treatment of it. Denworth comes close to giving us that, with fascinating and moving interviews with pioneers such as Graeme Clark, the founder of Cochlear Corporation, and Michael Merzenich, who did pioneering work at UCSF in the physiology of hearing and in brain plasticity. She also gives welcome credit to patients such as Rod Saunders and Charles Graser, who had test devices surgically implanted into their heads at great personal risk. She captures the tension and drama of those early experiments. For example, in 1978, Clark finally tried testing Saunders in a relatively realistic way:
Until then, they had done only closed sets—reciting words that were part of familiar categories, such as types of fruit. Speech in real life, of course, isn’t so predictable; open-set testing throws wide the possibilities. Angela Marshall was hesitant, fearing it wouldn’t work. “I said, if we fail, we fail,” says Clark. As the group stood watching with bated breath, Marshall presented one unrelated word at a time.
“Ship,” she said.
“Chat,” replied Saunders. Completely wrong.
“Boat,” said Saunders. Closer.
“Rich,” said Saunders. He had gotten one right!
By the end of the tests, Saunders had gotten 10 to 20 percent of the open-set words correct. That’s not the least bit impressive by today’s standards , but it was hugely significant at the time for a man who was profoundly deaf. Clark was overcome . “I knew that had really shown that this was effective,” he says. He pointed down the hallway of the hospital where we sat. “I was so moved, I simply went into the lab there and burst into tears of joy.”
The invention of these devices is a hugely important and dramatic event that deserves a full-length book treatment. Denworth has not given us this, but she has given us important parts of one.
The book also gives us a sweeping overview of advances in the science of hearing and cognition. She discusses, for example, the work of neuroscientist Helen Neville, who spent decades studying how deafness alters the way the brain processes sound and language. She discusses research using advanced brain-scanning equipment, such as that done by Anu Sharma and David Poeppel, who are trying to work out what exactly happens in the brain on a neural level after sound hits the eardrum. The bottom line, Denworth says, is that while scientists have learned a great deal about the detailed physiology of the brain, they are still struggling to explain how the brain actually understands language. She writes, “I heard a radio interviewer ask esteemed neuroscientist Eric Kandel of Columbia University what mysteries remain about the brain. ‘Almost everything,’ answered Kandel.”
“Almost everything” accounts for why, despite the voluminous research that Denworth has assembled and synthesized, there is still remarkably little concrete advice to be given for teaching deaf children how to hear. General principles are well known: the sooner a kid has access to sound, the better; exposure to a language – any language – early on is critical; the more language interaction a kid has with parents and peers, the better; in teaching reading, attention to the phonetic sound of language is crucial; and, unfortunately, it helps to be wealthy and privileged, because in such households language is used more often and more richly. And so on.
But concrete advice is sparse. There still is no How-To manual that makes raising a deaf child as straightforward as a craft project in a garage. Not that such a thing will ever be possible, because every deaf child is deaf in a different way, requiring a unique and specialized approach. And that is a job that will inevitably fall to the parent. (Parents and CI users should also read Leigh and Christiansen’s excellent book Cochlear Implants in Children: Ethics and Choices. While now dated with respect to the technology, it still offers a great deal of excellent material on language acquisition and many other matters related to CIs.)
Still, some things have been learned. Denworth questions the common assertion that learning ASL diminishes a deaf child’s ability to master spoken language. She discusses the work of Marc Marschark, who has written, “There has never been any real evidence that learning to sign interferes with deaf children’s learning to speak.” Indeed, Denworth writes, the exact opposite may be true: the process of learning two languages simultaneously may in fact enrich the developing brain. Accordingly, she brings in an ASL tutor in an effort to expose Alex to sign language. This fails, largely because Alex doesn’t get very interested. But also, she points out, just exposing a child to ASL with periodic tutoring simply isn’t enough to teach them the language. A second language has to be learned fully and immersively, and maintained over time, to yield cognitive benefits. And that is hard to do with ASL because it is very much a minority language.
Denworth offers a fascinating discussion in recent research in the importance of executive function in learning language. Executive function refers the brain’s ability to integrate various streams of information — basically, it’s the ability to synthesize them and work with the results in a controlled way. “The fact that many deaf children show delays in age-appropriate language means they may also be delayed in executive function,” Denworth writes. “Too much structure or overprotectiveness— something parents of deaf kids are prone to—compounds the problem by further stifling the development of executive function skills.” I can relate to this personally, because my parents, while loving, were not overprotective: every summer they tossed me into the clutches of a sleepaway camp, where I had to learn to fend for myself. I hated a good deal of it at the time, but it certainly taught me, ah, executive function.
She also writes of the cognitive benefits of music and poetry. “Old-fashioned children’s rhymes such as Mother Goose include alliteration, assonance, rhyme, and repetition…kindergartners who got more musical training demonstrated greater phonological awareness than those who got less,” she writes. I concur with this too. My parents also tossed me into Hebrew school, which bored me most of the time, but the frequent singing trained my ear for the rhythms of language. I played the recorder in the fifth grade, no doubt producing a howl more like a dog’s than the Philharmonic’s, but it was exactly what my brain needed at the time. My fascination with poetry led me to memorize many poems – I can still recite Yeats, Stevens, and Tolkien by heart – and that shaped my sense of the rhythms and prosodies of the spoken word.
These are all helpful things to know and do, but basically, the sum total of scientific advice still comes down to this: Deaf children need full exposure to a language —any language— as soon as possible. “Early access to language— any language— and parent-child interaction matter more than anything else,” she writes.
Denworth also discusses the important new issue of bilateral implantation. I’ve been bilateral since 2007, but a good deal of the science Denworth covered was new to me. “The average hearing person can find the source of a sound to within seven degrees of error,”Denworth writes. “Bilateral implant patients can do it to about twenty degrees.” I don’t think I could do it that well, because my ears are so different, as I frequently discuss in my blog entries (such as here). Unfortunately, Denworth overlooks Arlene Romoff’s “Listening Closely: A Journey to Bilateral Hearing,” which would have enriched her discussion. This is surprising, given how comprehensive her research has been.
Cochlear implants are not universally successful; Denworth discusses the wide variation in outcomes. Some children don’t do that well with cochlear implants, and reasons why are complex and often difficult to untangle. But they are usually successful, and that success rate is increasing. In a moving paragraph, Denworth writes,
But hearing aids alone had not been enough for Alex. The transformation came with the cochlear implant. Like the difference between candles and fluorescents, Alex’s residual hearing registered the world dimly and imprecisely except within a few small circles of light, while his cochlear implant lit everything up brightly if unnaturally. Once he had seen everything clearly, he could make better use of the warmth and ambience he got from his natural hearing, and he knew what lay in the shadows. Language followed.
“I Can Hear You Whisper” has many strengths, but perhaps the greatest is how Denworth has synthesized an enormous amount of material and crafted a compelling and clear book out of it. I’ve spent a great deal of time sifting through scientific papers myself, and I can attest to how hard it is to figure out which ones are truly important and to write about them in a clear and compelling way. This book is a compelling achievement and will be essential reading for parents, cochlear implant users, and anyone interested in the physiology of hearing for a long time to come.