English Archives - The Writing Brain

What is dyslexia? What causes it?

Posted on July 31, 2019 by rwwiley

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

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

Posted on April 25, 2018 by rwwiley

“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”

Why is English spelling so strange?

Posted on April 23, 2018 by rwwiley

You may have had this experience before: you look at a word, and think to yourself “That can’t be how it’s spelled… is that right?” … that first R in February just looks wrong, sometimes. You may also have found yourself at some point asking your English teacher why something is spelled the way it is. If you got more than a response of “Because it just is.”– you’re lucky! Few people study orthography (the part of language concerned with letters and spelling), and fewer stills its history. However, we actually can find a lot of information about why words are spelled the way they are, by learning about their etymology—the chronology of a word’s form and meaning from its earliest (recorded) sources to current usage and spelling. It is a bit of a myth that English spelling is so strange because it is entirely random and arbitrary

The English language is a famous borrower—with roughly 200,000 words in the English lexicon (vocabulary), tens of thousands of words have been borrowed from several other languages, in particular Latin and French, which together account for half or more of the sources of modern English words. Other words are derived from Germanic languages, Greek, Spanish, Italian, Arabic, Chinese, you name it—and as a consequence of this global borrowing, there is added diversity in the spellings of words. This is because English orthography is relatively opaque: the relationship between letters and the sounds they represent is far from a perfect 1-to-1 mapping. For example, ‘K’ usually represents the phonological form (sound) /k/, a hard sound like in “kid”—but sometimes it’s read as /n/ like in “knife”, where it is part of the digraph (two letters that represent a single unit) ‘KN’. The letter ‘C’ is especially challenging—it can also represent the hard /k/, like the second ‘C’ in “circle”, but also the sound /s/, like the first ‘C’ in that same word! Or it can be part of the digraph ‘CH’, which can represent the sound /tS/ like in “choose”. And of course, there are those dreaded silent letters, like the ‘C’ in “indict”!

So, why is English spelling so irregular? It turns out that there is some method to the madness, which is beautifully described by D.W. Cummings in his book “American English Spelling”. The gist of it is, our spelling system as a whole is the result of a balance between competing ideas of what a words spelling should convey. You might think that the letters we use to spell a word should just tell us its sound—this is the phonetic demand. What would happen if we took this demand to the extreme, however? Should we spell the same word differently depending on the accent of the speaker—should “car” be spelled k-a-r for some of us but k-a-h for Bostonians? Should we spell homophones, words that have the same sound but different meanings, the same way—“two to many to count” becomes “too too many too count”? And how about the ‘S’ at the end of “cats” versus “dogs”—the first is pronounced as an /s/ but the second as a /z/ (say it aloud to yourself if you don’t believe me!)—should we write “It’s raining kats and dogz!”? A purely phonetic system, then, becomes problematic, because some sounds have multiple meanings, and because some words have multiple acceptable pronounciations.

Much of the oddness in our word spellings, then, comes from a desire to use the orthography to disambiguate meaning, or to give clues to the origin of the word (and, ideally, its definition). We want to spell “dogs” with an ‘S’ so that we consistently write our plural marker with that letter. For another example, although the ‘G’ in “sign” is not pronounced, it allows us to see its relationship with other words like “signature” (and not confuse it with “sine”!).

Admittedly, the system could be improved. Some of the oddities are no longer practically useful. Unless you speak Latin, the silent ‘C’ in “indict” or the ‘B’ in “debt” are not very helpful (they’re re-introduced nods to the original Latin “indictare” and “debitum”). In fact, several letters of the alphabet could probably be done away with entirely, if we were only willing to let go holdovers from their sources (for example, ‘X’ could be replaced with “ks” or “gz”). Ultimately, changes in spelling, like changes in language in general, occur continuously and naturally through social processes—what’s “here” today may be “gon tomarow”.

Links:

http://www.dwcummings.com “A Site for spellers, teachers of spelling and reading, and students of English words”

https://www.etymonline.com Online etymological dictionary

https://en.wikipedia.org/wiki/English-language_spelling_reform

Further reading: Chapter 1 in Cummings, D.W. (1988). American English Spelling. JHU Press: Baltimore.