myths Archives - The Writing Brain

Dyslexia is surely one of the most recognized learning disabilities, yet also one of the most commonly misunderstood. One difficulty is simply that the term is used in different ways by different groups: teachers, education specialists, and psychologists will likely all provide different definitions of dyslexia.

In common language, ‘dyslexia’ usually refers to difficulties with reading, but very often challenges with spelling are also present (although the term for a problem specifically with spelling is dysgraphia). And unless otherwise specified, dyslexia usually refers to a developmental dyslexia, meaning a reading/spelling deficit appearing in children as they mature. This is opposed to acquired dyslexia, meaning the loss of reading ability after a brain injury, such as a stroke (for more on acquired dyslexia and dysgraphia, read here).

ramus2019img — An illustration of the core phonological deficit in the brains of dyslexic children (Ramus, 2014; accessed from here on July 30, 2019). In yellow are the parts of the brain (left superior temporal lobe) sensitive to phonology in ***both*** dyslexic and typical readers; in the green circle is the part of the brain (left inferior frontal lobe) known as Broca’s area, a key area for higher-level processing of speech. A leading theory maintains that it is the *connection between* these two areas that is primarily responsible for dyslexia, and that genetic factors determine the strength of this connection.

There are a lot of myths and misconceptions about dyslexia (do a quick web search for “dyslexia myths” and you’ll find lots of great information debunking them), one of which I’ve written about previously (see here). What it all boils down to is that dyslexia is a difficulty with mapping between the written word and its sound and meaning—but this difficulty can arise in different ways, depending on the individual and the language being read.

Dyslexia rates are highest in languages that use what is known as “opaque orthography”, like English, and lowest in languages that have transparent orthography. What’s the difference? English has a very opaque orthography—think of words like “ghost” (what is that ‘h’ doing there?) and “island” (not ice-land or is-land!). Most English letters can be pronounced multiple ways, sometimes even within the same word (the ‘c’s in “circle”). Even worse, most English sounds can be spelled multiple ways (like the vowel sound in “wait”, “late”, and “freight”… for more on why English spelling is so weird, see this post here). Other languages, like Spanish and Italian, have much less complicated relationships between letters and their sounds. So for example, at the end of first grade, children learning to read English make more errors when reading (67% in the United Kingdom) than those learning French (28% in France) or Spanish (8%; Dehaene, 2009).

Probably the main reason dyslexia is more diagnosed in English-speaking children is because the “core deficit” of dyslexia is actually one related to phonology: a disability with learning how to map between letters and their sounds (see Ramus, 2014). This means that for most children, the best way to overcome dyslexia will be educational interventions that focus specifically on phonology and how to ‘sound out’ words. Moreover, this seems to be largely genetically determined. While there may be associated deficits in areas besides phonology, the underlying source of difficulty for these children is in mapping between letters and sounds.

However, there are some children whose reading difficulties are not related to phonology, but instead to deficits in memory, attention, or vision (although this issue remains controversial). Only an educator or psychologist with special training can distinguish between different underlying cognitive deficits, as it requires comparing and contrasting performance on carefully chosen tasks. It’s also worth mentioning that for acquired dyslexia, there are clearly defined sub-types, some of which have nothing at all to do with phonology.

In summary:

Dyslexia is a difficulty with relating the written word on the page (or a screen!) to sound and meaning
Dyslexia in children, known as developmental dyslexia, is primarily (although not exclusively) caused by a deficit in phonology, determined by genetic factors
Dyslexia is not a sign or symptom of low intelligence; it is not a visual problem with seeing letters correctly or controlling eye movements

“Aoccdrnig to a rscheearch at Cmabrigde Uinervtisy, it deosn’t mttaer in waht oredr the ltteers in a wrod are, the olny iprmoetnt tihng is taht the frist and lsat ltteer be at the rghit pclae. The rset can be a toatl mses and you can sitll raed it wouthit porbelm. Tihs is bcuseae the huamn mnid deos not raed ervey lteter by istlef, but the wrod as a wlohe.”

You’ve probably encountered that paragraph before (or, if you’re like me, a bunch of times—it seems to go viral every other year!). How true is this claim that “the human mind does not read every letter by itself, but the word as a whole”? The first part has some truth to it—we do not focus on each letter in a word as we read—but the second part is very misleading! It is a pernicious myth that we learn to read by memorizing words as a whole shape. And it’s easy enough to come up with examples where jumbling letters in this way is a real problem—calm becomes clam, blow becomes bowl, etc. So, what do we actually need to look at, when we’re reading?

As you’re reading this sentence, you might feel that your eyes are moving smoothly across it. In fact, when we read text, whether its on a printed page or a computer screen, our eyes more in a series of short jumps, called saccades. These saccades are very fast, around 20-35 milliseconds, and in between them our eyes fixate on the text. These fixations can be brief (150 milliseconds), or relatively long, say one half of one second.

So, what is it that we look at during these periods of fixation? It is true that we do not focus on every single word when we’re reading—this is more or less for two reasons. First, we’re able to perceive several letters within the fovea (the center of our gaze): in languages like English, which are written from left to right, we can see a few letters to the left of our fixation and maybe 12-15 to the right (in languages written from right to left, like Arabic and Hebrew, readers can perceive more letters toward the left of fixation that the right!). This means that during each fixation, we take in a few words at a time, unless there are very long words. When we saccade to our next fixation, we are able to skip over some words because we actually have already seen them. This means, of course, that one of the challenges of reading is remembering the words and letters you have recently seen (in working memory) and integrating them with new information, as you continue to saccade through the sentence.

The second reason we do not need to fixate on every word is because we are often able to predict what words are going to follow—and we can use this ability to predict to speed our reading. This is often true of function words (words like “to”, “the”, and “do”), but also in sentences where the context leads to a very high probability for a certain word. Imagine that in one fixation you read “They sang Happy…”—you can guess that almost definitely the next word is “Birthday” (in fact, when we read sentences where we expect one word and it ends up being another, this surprise has consequences—it will cause us to slow down dramatically in our reading speed and often to double back and re-read!).

How do we know these things about reading? Mostly through the use of a machine called an eye tracker, which allows us to know (with very high temporal precision) where someone is looking. There are many videos online where you can see demonstrations of an eye tracker at work. This one in particular “How we read shown through eye tracking”) shows how we move our eyes from one line of text to the next—and how this is affected by the way that the lines are (or are not) justified!

Links:

“Eye movements in skilled readers”

“What eye movements during reading reveal about processing speed”

“How we read shown through eye tracking”

myths

What is dyslexia? What causes it?

Is it true that we don’t look at every word when we’re reading? What are our eyes doing when we read?