I Can Hear You Whisper Page 25
The story is proof, for Merzenich, of why it’s so important to understand exactly how the brain changes with experience. “[Hubel and Wiesel] did fantastic science, and the description of the critical period was brilliant,” he says, but he argues that the cast on the interpretation—the idea that the window of development slammed shut so firmly—was wrong. “It had very destructive negative consequences. What it meant in American society—and world society—was when you came to the schoolhouse door, what you saw was pretty much what you had. Kids were in a sense doomed to their genetic fate. It was imagined by pediatricians and child psychologists and schoolteachers everywhere that your brain was fixed and it was all about compensation for the circumstances in front of you.”
Merzenich’s groundbreaking work with monkeys in the 1970s, at the same time as he was contributing to the invention of the cochlear implant, showed that brains can and do continue to change throughout life. “It’s a revolution,” he exclaims, “understanding that in a sense we are continuously remodelable, that in fact, our fate and our ability are under our direction and charge. To understand that we can at any point improve, bodily improve, the things we do in life and that this science can be applied to change the outcomes of children on a large scale, this is revolutionary. It will come into every aspect of human societies—pretty soon it will be everywhere.”
One place the understanding has already arrived is the classroom. The effort to take what we know about brain development and make use of it in schools has been christened “neuroeducation.” From studies of executive function in toddlers to research on math ability in adolescence, all of the work takes as its foundational principles that learning is driven by brain circuitry and that brain circuitry is wired by experience.
The transition out of the laboratory is not always smooth. Not every basic scientist wants to wade into the classroom or the home and apply what has been learned. Those who do sometimes seem to be tripping over one another in the race to create scientifically based curriculums and video games (Merzenich was one of the first to market such a product, a reading intervention program called Fast ForWord). For their part, educators are not always happy to see the scientists. The two groups don’t always speak the same language or share the same immediate goals; a school principal focused on seeing test scores go up will not want to wait for a double-blind study from which some children, by design, won’t benefit. Furthermore, educators have grown suspicious of perennial promises of the next big thing in learning as well as defensive over complaints about the job they are doing. Nevertheless, it’s undeniable that researchers today do know far more than they used to about how children learn and how their brains develop.
To talk about some of the knowledge underpinning this new trend and see how it might apply to Alex, I turned to Helen Neville at the University of Oregon and the program she and her colleagues have been working on with a local Head Start for nearly a decade. Given that Neville set out to change the world back in the 1960s, it’s not surprising that she thinks it’s incumbent on scientists to try to use their work to improve children’s lives. “Now we’re seeing where the rubber meets the road,” she likes to say.
“It all starts with basic research,” she tells me. “You can’t jump in and pull an intervention out of the air. You have to know what systems show neuroplasticity, what ones are vulnerable, how fixed they are, how changeable they are, and what are their mechanisms, so you can target them. I’ve been studying this for thirty years. I’ve kind of come full circle, I think.”
The connection between preschoolers trying to pay attention and deaf adults exhibiting better vision in the periphery may not be immediately obvious, but there is actually a straightforward plotline to Neville’s story of scientific discovery, and her areas of focus have a special resonance for me. She began by studying the brains of deaf and blind people because their experiences were so unlike those of hearing and sighted people. “You had to start with a population that would give you a good chance of finding a difference,” she says. From there, she moved to people who had had slightly different experiences, such as second language learners or those who learned sign language instead of spoken language. And finally, she looked at typically developing children who have different experiences “just by virtue of being different ages or in different stages of cognitive development.”
All of the work is ongoing, but after thirty years Neville has sketched out a nuanced picture of how the brain’s systems of vision, audition, language, and attention change with experience. As Mike Merzenich maintains, the window does not necessarily shut firmly all at once. But neither, emphasizes Neville, does it stay open indefinitely for every skill. The details of what she calls “profiles in plasticity” matter. Some brain systems are so hardwired that they are the same whether a person hears or sees or not. Some change considerably with experience, but only during particular windows in development, which are in turn determined by the specific system in question—hearing has one, language turns out to have several. And then there are certain parts of the brain that continue to be shaped by experience throughout life, “with impunity,” says Neville. Knowing all of this has allowed her to chart “a road map of plasticity.”
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It was a map I thought would be useful to have in hand for what it could tell me about the remaining uncharted territory of language learning. Elissa Newport had given me a glimpse of how the brain approaches learning language. David Poeppel laid out a plan for how language works once we’re good at it. Helen Neville was going to connect the dots.
No matter how many languages a child learns before the age of seven, they will all operate in the brain in a similar fashion once they are acquired. Additional languages learned later are processed differently, and Neville tries in part to pinpoint those differences. Work from her laboratory and others has demonstrated that there are different profiles in plasticity for phonology, syntax, and semantics. As a result, scientists have created something like an evolving account of the development of language in the brain, allowing us to follow along as a child’s linguistic capabilities mature. The definition of an adult response can vary, depending on the skill—some responses become smaller and more efficient over time, others more widespread. What matters is the change in the way neurons do their work, a sign that they are wiring together with use or being pruned from disuse.
It won’t surprise anyone who has mangled the sounds of a second language—that is, most of us who didn’t start to learn until high school—to know that the window for phonology, the ability to recognize speech sound contrasts, opens and closes early. Generally, we will have an accent in any language we learn past the age of seven. As babies, we are already working on the underlying skill, learning to distinguish the sounds of our native language—the ones we’ll need—from sounds we don’t need. This is the process by which English babies learn the difference between “r” and “l,” but before the end of their first year, Japanese babies let that distinction fade, since Japanese doesn’t contain those sounds. Furthermore, the better babies are at responding to the contrasts of their native language at the ripe old age of seven and a half months, the more proficient they are at language as toddlers: Their word production and sentence complexity at twenty-four months are higher and so is the mean length of their utterances at thirty months. In Neville’s laboratory, they found that in thirteen-month-olds the brain response to known words differs from that to unknown words and is broadly distributed over both hemispheres. By twenty months, the effect is limited to the left hemisphere, more as it is in adults, reflecting increased specialization, vocabulary size, and maturity.
The ability to chop up language into usable chunks—to segment it—is also different in late learners. They can do it, of course, or they wouldn’t be able to make any sense of the new language, but they do it much more slowly. The “word onset effect,” part of the N1 that comes early in native speakers, isn’t as visible in late learners.
Starting e
arly with language doesn’t just get rid of accents, it also makes it much easier to handle grammar and produce the appropriate sentence structure fluently. We acquire those syntactic skills nearly as early as we master phonology. An early study by Elissa Newport shows this starkly. In English-Korean speakers who came to the United States at varying ages, scores on a test of English grammar drop off steeply between the ages of seven and seventeen. At two, children’s brief sentences already reflect the word order of their native language, so those learning English know that “Daddy” comes before “eats” and “pizza” comes after. (This is the very skill that Janet Werker attributed to prosody.) Between the ages of three and five, children are already experts at such grammatical fine points as how to describe something that happened in the past, how to ask a question, how to say that you don’t want or like something. They hit these milestones no matter what language they are learning, which, as Neville has pointed out, “supports the proposal that language learning has a significant biological basis.”
Differences don’t just show up in second language learners. How proficient you are in your native language is evident in your brain as well. It’s a rather infamous fact that much cognitive research is done on college students—if you are a researcher at a university, students are handy and cheap. But are they typical? When he first started reading up on the literature describing how the brain was organized for language, Neville’s colleague Eric Pakulak found it fascinating until he looked at the methods section in one particular paper. “It’s twenty undergraduates from Harvard,” he says. “That’s not really representative.” As it happens, Pakulak plays rugby with a group of men who do represent a wide swath of the socioeconomic spectrum. So he decided to test a group that included some of his teammates and others who weren’t university students. He looked at two particular responses in the brain that reflect syntactic processing (grammar): the early anterior negativity, a wave that falls somewhere between a hundred and three hundred milliseconds and is relatively automatic; and the more controlled P600, the late wave thought to reflect repair and reanalysis. In higher-proficiency speakers, Pakulak found that the early response was more efficient and more concentrated. He hypothesizes that this “frees up” mental resources for the later response, which is larger and more widespread.
For those who miss out on developing the early responses, there are alternatives. Pakulak also studied Germans who spoke English as a second language. Because of the consistency of the German educational system, all had begun learning English around the age of eleven or twelve—late in brain terms—but all were good at it. (This is the university bias at work again: All the subjects were undergraduates, graduate students, or professors.) Pakulak found that the late start on English meant the Germans lost the benefit of the early response, but they made up for it by putting more brain areas to work later in the process. “They’re using different resources to achieve a different level of proficiency,” he explains. “They’re using more controlled processes because they don’t necessarily have the access to these early and automatic processes that are more constrained by differences in experience.” Those results reminded me of what Greg Hickok told me: that anyone, like Alex, who got less input, was going to have to use more top-down processing. The same apparently was true of German graduate students who wanted to study in the United States.
Here’s the good news: We can keep learning new words in any language for as long as we like. “This is a system that continues to change throughout life,” says Neville. “It can be set up in a native-like fashion even if you start learning a language at the age of thirteen or fifteen.” In Chinese-English bilinguals who started learning English either very young, as preteens, or later, the systems in their brains that handle semantics look “completely identical no matter when English is learned.”
No matter what language we’re learning or when, it helps to pay attention. “When you focus on something specific, the brain produces a bigger response to it,” says Neville. Many changes in vision, audition, and language observed in neuroplasticity studies depend in part on selective attention. (This was true of Merzenich’s monkeys, by the way. The changes in cortical areas came only when they paid attention to the spinning disks they were being asked to touch.) I remembered that David Poeppel had said he could tell by glancing at an N1 whether the listener had been paying attention. In fact, the response can be 50 to 100 percent stronger, says Neville. Children’s ability to pay attention matures just as their language does, but even at the age of three they are able to listen to one story over another, and when they do, there’s a visible change in their brains.
• • •
To show me how they test that in the lab, Eric Pakulak puts me in a soundproof booth where there are speakers to my left and right and a television screen in front of me. From the control room, he starts playing both audio and video. In my right ear, I hear the children’s story of the Blue Kangaroo. In my left, another children’s story, from the Harry the Dog series, is playing. I’m supposed to listen to the Blue Kangaroo story and ignore Harry. On the screen, pictures corresponding to the kangaroo story help me in my efforts to focus. When I zoom in on the story mentally—focusing the flashlight of my attention, as neuroscientists say—I find that I can do it. Harry fades to the background. But every so often, my attention wanders and Harry leaps back into my awareness. I have to work to keep him in his place.
In the actual test, the subjects would be wearing electrode caps for EEG recordings. Superimposed on both stories, there are extra beeps serving as auditory probes. What Pakulak, Neville, and their colleagues are really measuring is the neural response to those probes. They wanted to see if the response was larger when the subjects were paying attention. The answer was yes. In adults, it’s about twice as large. Although the response is different in children of six, seven, and eight, there is still a clear enhancement when the children pay attention.
The real-life consequences of paying attention—or not—play out in the classroom. Those who are less focused learn less. It’s that simple. Brain circuitry drives learning and it does a better job of it when the networks are working at optimal levels. I am not talking here about attention deficit disorder, which is a problem of a higher order, though obviously one on the same continuum. I’m just talking about the more routine ability to listen to the teacher or keep one’s concentration on the page.
There is more than one kind of attention, it turns out, and the various forms also have different profiles in plasticity. Sustained selective attention, the kind that is particularly useful in a classroom, takes a very long time to develop. On the one hand, that explains why it’s so hard for small children to stay focused. On the other hand, it means the window of opportunity to help them do it better stays open for longer. Neville has found that children of lower socioeconomic status have trouble with selective attention, particularly in tasks requiring the filtering of irrelevant information.
With so much work under her belt, Neville decided it was time to take what she knew about neuroplasticity and figure out how to use it to help children. “We’ve reached the point where we’ve learned an awful lot,” Pakulak tells me. “We’re taking those results and having them inform our development of intervention and training programs.”
They started with attention for several reasons. It qualifies as a clear example of Neville’s concern that what is enhanceable in the brain is also vulnerable—strengthened, attention helps; weakened, it’s a major problem. The good news was that it seemed that attention might be trainable. “If you have a measure that’s a predictor of being at risk for delays, that gives you a lot of information,” says Pakulak. Attention training might provide a lot of bang for the buck because its effects would be widely felt. It was also a necessary fundamental skill. “Having intact sensory and cognitive systems is really not worth that much if you do not have control of your emotions or have good social cognition,” says Neville. That point informs a wide range of current neuroeducat
ional interventions, which most commonly home in on emotional regulation and executive function.
Pulling together the many pieces of the program took time, but now Neville’s group has some intriguing results. One hundred forty-one three-to five-year-old children enrolled in the Head Start program were randomly assigned to three groups: One group simply continued to attend Head Start; a second got attention training during the school day for forty minutes a day, four times a week, with three sessions for parents over eight weeks; and the third section brought children and parents to the facility once a week for eight weeks for the children to receive some form of training and the adults to get proven strategies for parenting.
In addition to Dr. Distractor, the attention training included exercises like “Emotional Bingo,” in which kids took cards with the names of emotions printed on them, showed what those emotions look like and how they feel, and then learned techniques for calming down, like taking a big “bird breath” and saying, “Oh, well.” Children also worked on focusing attention by playing games that required them to start and stop listening, looking, or moving when teachers cried “Freeze.” In parenting sessions, “we assessed the way they used language with children, and we encouraged them to engage in more balanced turn taking,” says Pakulak.