The Dyslexic Advantage (5 page)

This list of challenges may make it seem that individuals with dyslexia face a whole host of different “problems.” Actually, all these findings can be traced back to a small number of variations in brain structure and function. It's only because these variations occur in basic processing systems that are used for many different functions that they can give rise to such a wide variety of “symptoms.”
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For most individuals with dyslexia, it's likely that only a very few underlying variations are responsible for all their dyslexia-associated findings. This is true even for many of the individuals with dyslexia who receive multiple diagnoses, like dyslexia “plus” attention deficit disorder, dyspraxia, developmental coordination disorder, or auditory processing disorder.

In this chapter and the next, we'll look at four important brain variations that have been found to be associated with dyslexia. We'll examine how these variations in brain function or structure may be responsible for both the dyslexia-associated challenges we've listed and the dyslexic advantages we'll discuss in later chapters. Let's begin, in this chapter, by looking at two dyslexia-associated variations in information processing (or
cognition
).

The first pattern we'll discuss is a variation in the brain's
phonological
(or “word sound”)
processing system
. This system is used to process phonemes, the basic sound components in words. English has approximately forty-four phonemes, and just as the letters of our alphabet can be strung together to form printed words, phonemes can be strung together to form all the spoken words in English.

For the past thirty years most reading specialists have favored the
phonological impairment theory
as the most likely explanation of the brain basis of dyslexic reading and spelling problems. Think back for example to the definition of dyslexia cited in chapter 1, which states that dyslexia-associated reading and spelling difficulties “typically result from a deficit in the phonological component of language.”

There are several good reasons for believing that phonological impairments play a key role in causing dyslexic reading and spelling challenges. Problems with phonological processing have been found in at least 80 to 90 percent of individuals with dyslexia, and they can clearly contribute to many of the challenges mentioned earlier in this chapter. The role that phonological processing impairments play in the reading and spelling challenges many individuals with dyslexia display has been especially well worked out. While we'll save a fuller discussion of this role for our chapter on reading, there are several key points we should mention here.

The phonological processing system plays a key role in analyzing and manipulating the sound structures of words. Many of these functions are important for matching word sounds and the letters used to represent them—that is, for mastering the rules of phonics which underlie decoding (or sounding out words) and encoding (or spelling words). Two of the most important phonological processing (or
phonological awareness
) tasks underlying these skills are
sound segmentation
(or the ability to split incoming words into their component sounds) and
sound discrimination
(or the ability to distinguish word sounds from one another). Most individuals with dyslexia struggle with one or both of these tasks and as a result have difficulty mastering the basic skills underlying reading and spelling.

Even though phonological processing involves low-level or fine-detail language processing—that is, processing of the most basic building blocks of language—it forms the foundation for the entire language structure and supports many of the higher language functions. That's why severe problems with phonological processing can cause difficulty at all levels of language, such as mastering word meanings, learning how words interact when used in groups (that is, grammar and syntax), and understanding how words work together to form “discourse-level” messages like paragraphs or essays. When the higher-order language problems resulting from phonological impairments are severe, they are called “specific language impairment,” but the underlying process remains the same.

The phonological processing system also plays an important role in many attention-related functions, including working memory and executive functioning.
Working memory
is the kind of short- to intermediate-term memory that helps us “keeps things in mind” for active conscious processing—very much like the random-access memory or RAM on your computer. The phonological processing system forms a
phonological loop
(or short-term memory tracing) that keeps auditory-verbal information alive in active working memory until it can be processed, organized, and put to use.

When auditory-verbal working memory is limited (or has too short a functional span), the brain may fail to finish all the processing it needs to perform before this “internal speech tracing” fades away. The result is
working memory overload
, which causes symptoms like inaccurate language processing, slower language-based learning, problems with organization and task management, and the appearance of inattention during difficult work. Working memory overload resembles what happens when you try to run a memory-intensive software program on a computer with too little keyboard memory. At first the program runs more slowly; then it begins to flash error messages; and finally it jams up completely.

Problems with working memory overload are very common in dyslexic students. They often first appear during the early elementary years, when complex tasks like reading, writing, and math are first introduced; peak again during the middle elementary years, when organization and study skills are first stressed; then cause another peak of challenges during middle and high school when language and organizational demands become even more complex.

Importantly, working memory also plays a key role in other aspects of attention or “executive function” like organization, planning, implementation, and oversight of tasks. That's why when working memory is limited due to problems with phonological processing, students can experience a whole range of challenges with attention. Often such students are diagnosed with inattentive ADHD.

Problems with phonological processing are usually attributed to structural variations in the brain's left hemisphere, particularly in the language areas of the left temporal lobe. The precise nature of these variations isn't fully known. Some researchers believe they are caused by alterations in processes that take place very early in development, when brain cells organize themselves into functional networks. Because the networks don't form in a well-integrated fashion, the processing of phonological information is impaired.
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Other researchers have proposed that these impairments are caused by difficulties in learning rule-based procedures or by inherited variations in the structure of the brain's circuitry. We'll discuss these hypotheses in more detail in the rest of this chapter and the next.

For the moment, however, let's focus on the key question of whether phonological processing impairments by themselves seem capable of causing all the challenges and strengths associated with dyslexia. It shouldn't take us long to see that they cannot. For example, there's no direct relationship between poor phonological processing and common dyslexia-associated difficulties like problems with finger coordination for handwriting, eye movement control for reading, or speech muscle control for speech articulation. Even more importantly, phonological processing impairments provide no explanation for the kinds of dyslexic advantages or dyslexia-associated processing strengths that we saw in Kristen, Christopher, and James—such as their strong mechanical and spatial abilities or their strengths in spotting unusual connections.

There must be some even more fundamental difference (or differences) in dyslexic brains that accounts for both phonological processing problems and the other patterns of challenges and strengths associated with dyslexia. Next, and in chapter 4, we'll consider the remaining three dyslexia-related brain variations, each of which attempts to provide this more basic explanation.

The next key difference between dyslexic and nondyslexic brains to consider involves the
procedural learning system
and procedural memory.
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One of the leading experts on procedural learning and dyslexia, British psychologist Dr. Angela Fawcett, described procedural learning and its relationship to dyslexia for us in the following way: “Procedural learning is learning
how
to do something, and learning it to the point where it's automatic, so you know how to do it without having to think about it. This process of becoming automatic with complex rules and procedures is much more difficult if you're dyslexic.”

At least half the individuals with dyslexia have significant problems with procedural learning, and as a result they'll be slower to master any rule-based, procedural, or rote skill that should become automatic through practice. Because most basic academic skills are heavily rule and procedure dependent, problems with procedural learning can cause a wide range of academic challenges, which are often especially intense in the early grades.

For example, most language skills require the constant, rapid, and effortless application of rules and procedures, including differentiating one word sound from another; correctly articulating word sounds and correctly pronouncing words; breaking words down into component sounds; mastering the rules of phonics underlying reading (decoding) and spelling (encoding); recognizing rhymes; recognizing how changes in the forms of words can change word meanings and functions (morphology, e.g.,
run
,
ran
,
running
,
runner
,
runny
, etc.); interpreting how differences in sentence organization and word order can affect sentence meaning (syntax); and recognizing language style and pragmatics (the language conventions that carry important social cues).

Many other academic skills are also rule based, such as rote (or automatic) memory of things like math facts, dates, titles, terms, or place names; memorizing complicated procedures or rules for things like long division, carrying over, borrowing, or dealing with fractions in math; sequences, like the alphabet, days of the week, or months of the year; writing conventions like punctuation and capitalization; and motor rules for forming letters the same way every time, when writing by hand, and spacing evenly between words.

Finally, individuals with procedural learning challenges also typically have difficulty learning simply by observing and imitating others as they perform the complete, complex skill—that is, by
implicit learning
. Instead, they learn better when rules and procedures are broken down into small, more easily mastered steps and demonstrated clearly—a process known as
explicit learning
. When you realize how important procedural learning is for most basic skills, you can see why procedural learning challenges have been thought capable of producing so many of the challenges associated with dyslexia.

Because individuals who struggle with procedural learning have difficulty learning to perform rule-based skills automatically, they must instead perform these skills using
conscious compensation
, or the combination of focused attention and active working memory. The drawback to this kind of highly focused processing is that if too many parts of a complex task must be performed consciously (because the basic skills haven't been mastered to the point where they're fully automatic), then working memory resources are very likely to be overwhelmed. Since individuals with procedural memory problems must perform many tasks using conscious processing, they will often experience working memory overload, which makes them slower and more error-prone than others on routine tasks.

Individuals with procedural learning challenges also tend to require many more repetitions than others to master complex skills. Dr. Fawcett explains: “You can teach a dyslexic child what the rules are, and she appears to grasp them, but then the rules slip away again. We actually came up with something we called the
square root rule
, which means that it takes the square root
longer
to learn something if you're dyslexic than if you aren't. In other words, if it took four hours to learn something for a nondyslexic, it would take twice as long for a dyslexic; and if it took one hundred hours it would take ten times as long. So you can see how much extra work is needed to get these children to develop skills similar to other children.”

Individuals with dyslexia and procedural learning challenges also tend to forget skills that they appear to have mastered more quickly than others if they don't practice them. “Often teachers will say, ‘This child seemed to have learned this before the six weeks' holiday, but now he's come back and it's gone.' It helps to show teachers that it's not due to a moral fault in the student or any lack of effort, but it's really something to do with the basic learning processes. Actually, the dyslexic child is working much harder than everybody else, and this difficulty in learning and retaining rules results from a fundamental difference in the learning process. When you understand this, you realize that it's not something the child should be ashamed of, but something he should be taught to get around, using specific strategies.”

From a neurological standpoint, procedural learning challenges are often associated with dysfunction in the cerebellum, a small, densely packed structure at the back and bottom of the brain. Although it accounts for only 10 to 15 percent of the brain's weight, the cerebellum contains nearly half the brain's impulse-conducting cells, or neurons. Although it was long thought to be involved primarily in helping with motor (or movement-based) functions, within the past decade scientists have come to realize that the cerebellum plays a critical role in most skills that become automatic through practice—whether those skills involve movement, language, “internal speech,” working memory, or other aspects of attention.