The Dyslexic Advantage (6 page)

There is now a wealth of evidence that at least half of all individuals with dyslexia experience difficulties with procedural learning. Typically, these individuals also show signs of mild cerebellar dysfunction on exam, such as low muscle tone; poor motor coordination; and difficulties with sequencing, timing and pacing, and time awareness.

This high incidence of procedural learning challenges in individuals with dyslexia has led Angela Fawcett and her collaborator, psychologist Roderick Nicolson, to propose the
procedural learning theory
of dyslexia, which posits that many of the findings of dyslexia are due to challenges with procedural learning. One of the great strengths of this theory is that it explains many of the symptoms commonly found in dyslexia that don't obviously relate to phonology or language, like challenges with motor control and coordination. We've found the procedural learning theory to be especially helpful for understanding and troubleshooting the learning challenges of individuals with dyslexia who show features like low processing speed scores on WISC IQ tests, very slow work output, motor problems with handwriting or eye movement control, problems with rote memory for things like math facts, more extensive problems with syntax or expressive language, special difficulties with sequencing, and poor time awareness and estimation.

Another strength of the procedural learning theory is that it predicts some of the advantages that we often observe in individuals with dyslexia. For example, while poor automaticity in routine skills makes many individuals with dyslexia slower and less efficient on routine tasks, it also forces them to approach these tasks with a greater “mindfulness” or task awareness and to really think about what they're doing. As a consequence, we've found that individuals with dyslexia often innovate and experiment with routine procedures, and in the process find new and better ways of doing things. In contrast, individuals with strong procedural learning abilities quickly learn to perform tasks in just the way they were taught, so they often perform these tasks without having to think about them. As a result, they less often feel the need to innovate. This kind of “flip side” benefit to dyslexic processing is just what we would expect to see from any full explanation of dyslexia.

Still, there are several drawbacks to the procedural learning theory as a complete explanation of dyslexia. Many individuals with dyslexia do not show clear procedural learning challenges, and many of the dyslexic advantages described in later chapters can't easily be attributed to increasing task mindfulness. For these reasons, a full explanation for both dyslexic challenges and the strengths must depend upon an even more fundamental feature of dyslexic brains. In the next chapter, we'll look at two variations in brain structure that may provide this deeper explanation.

Differences in Brain Structure

I
n 1981, Dr. Roger Sperry was awarded the Nobel Prize for his discovery that the brain's two halves, or hemispheres, process information in very different ways. Ever since, a steady stream of books and articles have popularized the idea that there are distinctive “right-brain” and “left-brain” thinking styles and that individuals can be primarily “right-brained” or “left-brained” in their cognitive approach.
¹
While these views of brain function are highly oversimplified, they still contain a good deal of truth: the brain's two hemispheres really do process information in very different ways.

As a rough generalization, the brain's left hemisphere specializes in fine-detail processing. It carefully examines the component pieces of objects and ideas, precisely characterizes them, and helps to distinguish them from each other. The right hemisphere specializes in processing the large-scale, big-picture, “coarse,” or “global” features of objects or ideas. It's especially good at spotting connections that tie things together; at seeing distant similarities or relationships between objects or ideas; at perceiving how parts relate to wholes; at determining the essence, gist, or purpose of a thing or idea; and at identifying any background or context that might be relevant for understanding the objects under inspection.

We can roughly summarize the functional differences between left and right hemispheres by saying that they specialize respectively in trees and forest, fine and coarse features, text and context, or parts and wholes.
²
These differences show up in important ways in the brain's various processing systems. Consider vision: when looking at an object, the left hemisphere perceives fine details and component features, but it's poor at “binding” those features together to “see” the larger whole. For example, the left hemisphere can recognize eyes and ears and noses and mouths, but it's poor at recognizing faces. Similarly, it can see windows and doors and chimneys and shingles, but it's poor at seeing houses. To perceive these larger patterns, the left hemisphere requires big-picture processing help from the right.

We're raising this topic because several kinds of evidence suggest that individuals with dyslexia differ from nondyslexics in the ways they use their brain hemispheres to process information. In particular, a growing body of research suggests that individuals with dyslexia use their right hemispheres more extensively for many processing tasks than do nondyslexics. Differences of this type have been shown for many auditory, visual, and motor functions, and some of these differences play a role in reading and language.

This dyslexia-related difference in the division of labor between the brain's hemispheres is the third variation we'll examine in our search for the factors underlying dyslexic strengths and challenges.

Several prominent writers have observed that individuals with dyslexia often show a distinctly “right-brained style” or “flavor” in the ways that they process information. A particularly strong case for this connection has been made by author Thomas G. West in his marvelous book
In the Mind's Eye
.
³
West—who himself is dyslexic—suggests that this right-sided processing pattern may be directly related to the visual and spatial talents shown by many individuals with dyslexia.
⁴

Scientists have also found that individuals with dyslexia use their right hemispheres more extensively for reading than do nondyslexics. This difference was first demonstrated in the late 1990s by Drs. Sally and Bennett Shaywitz at Yale, who used a brain scanning technique called functional magnetic resonance imaging (fMRI) to identify the brain areas that become active as individuals with dyslexia and nondyslexics read.
⁵
Reading expert Dr. Maryanne Wolf summed up the results of this work by writing, “The dyslexic brain consistently employs more right-hemisphere structures [for reading and its component processing activities] than left-hemisphere structures.”
⁶

While this increased right-hemispheric processing may at first appear to involve a “rightward shift” from the normal left-sided pattern, it actually reflects the
absence
of the usual “leftward shift” that occurs as individuals learn to read. Dr. Guinevere Eden and her colleagues at Georgetown University have shown that most beginning readers use
both
sides of their brain quite heavily—just like individuals with dyslexia. It's only with practice that most readers gradually shift to a largely left-sided processing circuit.
⁷

Individuals with dyslexia have a much harder time making this shift to primarily left-sided, or “expert,” processing. Without intensive training they tend to retain the “immature” or “beginner” pathway, with its heavy reliance on right-hemispheric processing.

This dyslexic tendency to retain the largely right-sided “beginner” pathway raises two important questions. First,
why
do individuals with dyslexia show this persistence of heavy right-hemisphere involvement? And second, what are the
consequences
of this persistence for dyslexic thinking and processing?

In approaching the first question, it's important to recognize that the reading circuit isn't the only brain pathway in which a right-to-left processing shift is produced by practice and experience. Transitions like this are seen in many brain systems, and they are thought to reflect our changing processing needs as our skills increase. The general idea goes like this.

When we attempt a new task, our right hemisphere's coarse or big-picture processing helps us recognize the overall point or essence of the task, so we don't get lost in the details. It also helps us recognize how the new task may be similar to tasks we've learned before, which helps us problem-solve and fill in details we miss. In these ways, the right hemisphere's top-down or big-picture processing is ideal for our early attempts to stumble through processes we're still fuzzy on. It's also invaluable when we try to tackle other tasks for which we lack the automatic skills to perform quickly and efficiently.

As we become more familiar with the purposes and demands of a task, our need for big-picture processing gives way to a demand for greater accuracy, efficiency, speed, and automaticity. That's where the left hemisphere comes in, with its greater ability to process the fine details that must be mastered to develop true expertise.

One well-documented example of a right-to-left-hemisphere processing shift that occurs with training is the shift that takes place as we develop musical expertise. Researchers have shown that untrained music listeners process melodies primarily with their right hemispheres, so they can grasp the large-scale features (or gist) of the melody. By contrast, expert musicians process music more heavily with their left hemispheres, because they focus on the fine details and technical aspects of the performance.
⁸

This tendency to shift from right- to left-hemisphere processing as skill increases is intriguing because it suggests that the dyslexic failure to make such shifts might reflect a kind of general difficulty in acquiring expertise through practice. As we said in the last chapter, many individuals with dyslexia show precisely such a difficulty, especially in mastering rule-based skills like those involved in reading. Delays in mastering rule-based reading skills could clearly slow the development of “expert,” left-sided pathways and cause prolonged dependence on the “novice,” right-sided circuits. Similar difficulties in gaining expertise might also cause the greater right-hemisphere processing that individuals with dyslexia show with the other processing tasks we mentioned.

If delays in developing automaticity and expertise at least partly explain
why
individuals with dyslexia use their right hemispheres more for many tasks, then what are the consequences of this more right-hemispheric processing style? We can begin to answer this question by looking at differences in how the right and left hemispheres process information, using language as an example.

In 2005, Northwestern University psychologist Dr. Mark Beeman published a remarkable paper describing the differences in the ways that the two brain hemispheres process language. When the human brain is presented with a particular word, each hemisphere analyzes the word by activating its own “semantic field,” or collection of definitions and examples describing that word.
⁹
Importantly, the semantic fields contained in the left and right hemispheres perform this analysis in significantly different ways.

The left hemisphere activates a relatively narrow field of information, which focuses on the “primary” (or most common, and often the most literal) meaning of the word. This narrow field of meaning is particularly well suited for processing language that's low in complexity or requires precise and rapid interpretation—like comprehending straightforward messages or following simple instructions. It's also useful for quickly and efficiently
producing
language. Since speaking and writing require the rapid production of
specific words
(rather than blended or compound words), the less ambiguity or hesitation the better. The left hemisphere's narrow semantic fields are ideal for such production.

The right hemisphere, by contrast, activates a much broader field of potential meanings. These meanings include “secondary” (or more distant) word definitions and relationships, like synonyms and antonyms, figurative meanings, humorous connections, ironic meanings, examples or cases of how the word can be used or what it represents, and words with similar “styles” (e.g., formal/informal, modern/archaic) or “themes” (e.g., relating to the beach, to chemistry, to emotions, to economics). This broader pattern of activation is slower, but it's also much richer. That's why it's particularly useful for interpreting messages that are ambiguous, complex, or figurative. Tasks for which the right hemisphere is particularly helpful include comprehending or producing metaphors, jokes, inferences, stories, social language, ambiguities, or inconsistencies.

We asked Dr. Beeman to illustrate the kind of “distant connection” that the right hemispheric semantic processing is particularly good at detecting. He responded with the following example. “Consider this sentence: ‘Samantha was walking on the beach in bare feet, not knowing there was glass nearby. Then she felt pain and called the lifeguard for help.' When most people hear that sentence, they infer that Samantha cut her foot. But notice that the sentence never explicitly states that she cut her foot, or even that she stepped on the glass. These facts have to be inferred, and these inferences are made by the right hemisphere. It produces these inferences by detecting the overlap in semantic fields between the terms
bare feet
,
glass
, and
pain.
”
¹⁰