Table of contents:
- Page 1: What is dyslexia?
- You’re here: Signs of dyslexia
- Page 3: Diagnosing dyslexia
- Page 4: Skills measured
- Page 5: How does it work?
- Page 6: Costing
The complexity of learning disabilities in general makes it difficult to pin-point a discrete set of definitive signs. This is further complicated by the fact that some behaviors or difficulties are interpreted differently depending on age and developmental stage. However, advances in dyslexia testing have enabled clinicians to link certain traits, behaviors and deficits to the presence of dyslexia. Here is a list of some of the more common ones:
Children tend to develop language in a predictable series of stages and landmarks. This process has received a great deal of attention from psychologists and linguists, so it is fairly well understood. There is also a correlation between a failure to reach certain landmarks, and difficulties with reading later on. While none of these are conclusive proof of dyslexia, they are worth noting if you observe them in your child:
Late language acquisition
Many dyslexic children exhibit a delay in language acquisition. Acquisition is the term linguists use to describe the process whereby you take on your first language. Children who take longer to grasp their first language may be at greater risk of dyslexia, because this can indicate a deficit in phonological awareness.⁸
Difficulty with rhyme
Most people learn short poems, songs and nursery rhymes in early childhood. These are usually rich in rhyme, which serves two purposes. The first is that it enables memorization. It’s easier to remember the next line of a song if its end rhymes with the one preceding. The second is that it lays a foundation for the linking of sounds and symbols that comes later on. A dyslexic child may find it difficult to answer a question like: “can you think of a word that rhymes with hot?”
Problems with literacy
Once a child completes the process of acquiring a first language (usually around the age of 5), literacy is introduced through elementary schooling. The child must begin to learn to interpret written text. In order for this to happen, several other mental processes must be effortless and routine. If difficulties in any of these begin to appear as a child begins learning to read, this could indicate the need for a dyslexia test.
Learning sound-symbol relationships
Persistent difficulty in linking letter symbols to sounds can be an early indicator of dyslexia. Some children routinely give the wrong sound for a given letter symbol, even ones that are frequent. If this persists even when the symbol is written in large font, the problem may be a specific learning disability like dyslexia.
In English, and many other languages, each character in a written word represents one phoneme, or sound. You can think of a phoneme as a unit of sound that bears meaning. For example, the difference between /t/ and /d/ is a salient one for English speakers: “debt” and dead” are pronounced in similar ways, only the ending of the word differs – but the ending changes the meaning. To successfully deal with a word, a beginning reader must “blend” the sounds represented by the various symbols: the sequence t – a – p must become a single sound: “tap”. Dyslexia can make it difficult for the young reader to do this, even for very simple words.
Difficulty substituting sounds
Just as they may struggle to blend sounds into words, dyslexics often do not readily do the opposite task of breaking words into separate sound segments. A task such as changing one sound for another may be very difficult: “change the ‘t’ in ‘tap’ into a ‘m’ to make a new word”.
Reading for comprehension
Effective reading involves more than accurate decoding of the text. The reader must understand what the text is saying. For this to happen, the reader must move at the right pace: too slow, and important information will be forgotten. Too fast, and the brain will not have adequate time to assemble meaning. Furthermore, the effort of decoding the words should not be so great that it leaves no time and energy for interpretation. Dyslexics, even those who are able to read adequately, might have significant difficulty putting the meaning of a text together. In young children, this can manifest in an inability to answer even very simple comprehension questions after reading a story.
In addition to language and literacy skills, a child’s behavior and non-verbal abilities can provide useful information about future reading outcomes. As with the previous examples, these are not conclusive, and you should not think of them as definite symptoms of dyslexia. But they are worth noting, and you should inform the examiner or assessor, if you do procure a dyslexia test for your child later on.
Retaining heard information
Dyslexic children often fail to follow verbal instructions. This can easily be mistaken for defiance or a deficit in hearing. But it might indicate a deficit in auditory memory, which is a crucial aspect of learning.
There appears to be a high rate of coincidence between dyslexia and difficulties with motor skills. These are the skills that we recruit in order to do things like sit and balance (gross motor), or hold and manipulate paper and pencils (fine motor). Dyslexic children frequently exhibit poor or below average motor skills, which suggests a link between the two.⁹ Even though this isn’t very well understood, problems with physical control can be an early sign of a specific learning disability such as dyslexia or dysgraphia. Some researchers have even suggested that a failure to crawl might be relevant to learning difficulties like dyslexia.
What are the underlying causes?
Any of these signs may concern an observant parent. What is sometimes even more bewildering is the fact that many children who exhibit these signs seem completely normal in every other respect. Sometimes, these children register above average skills in other aspects of their lives. So what causes these problems? This is the subject of lively and ongoing debate, but there are several theories.
Phonological deficit hypothesis
The idea that phonological weaknesses underlie dyslexia to some extent is a part of almost all theories about the causes of dyslexia. However, in its strongest form, the phonological deficit hypothesis proposes that dyslexia is caused by phonological deficits alone. The child with poor phonological awareness will have difficulty remembering, recalling and manipulating the sounds of their language. This gives rise to symptoms such as difficulty identifying words that rhyme, or breaking words up into their constituent sounds. As a child approaches school-going age, these weaknesses can impede literacy. This is because effective reading requires a child to master relationships between graphemes (written symbols) and phonemes (meaning-bearing units of sound in a language).
The notion that phonological deficits can completely account for dyslexia continues to be challenged, however. A growing body of evidence suggests that the relationship between phonological awareness and written language is much more complicated than previously assumed. Some studies have shown that learning to read actually influences a child’s ability to perform tasks that demonstrate phonological awareness. The strong version of this hypothesis is likely to continue to lose to more nuanced approaches.
An alternative to the phonological deficit theory is the magnocelluar theory. Magnocellular cells are neurons that form networks in parts of the brain. In particular, magnocellular cells involved in vision allow us to focus our eyes and counter the effect of motion or visual “noise”. On this theory, reading difficulties like dyslexia have a kind of physiological footprint; the magnocellular pathways of a dyslexic should show underdevelopment or abnormal development. This theory recalls 19th and 20th century models that construed dyslexia as a purely visual phenomenon, a point of view that gradually gave way to a more phonological understanding. Overall, the magnocellular theory is not widely favored and has limited experimental support.
However, it is possible that visual deficits might play a role. Obviously, vision is crucial to reading, so it is a good idea to assess a child’s vision before testing for dyslexia. An optometrist or physician can administer a test to ascertain whether a child has normal eyesight. Once you have ruled out poor eyesight as the cause of a reading difficulty, you can proceed with a dyslexia test.
Double deficit hypothesis
As the name suggests, advocates of the double deficit hypothesis point to weaknesses in two distinct areas. The double deficit hypothesis is an extension of the phonological deficit hypothesis, because it acknowledges the key role that phonological awareness plays in the act of reading. However, this hypothesis offers a more precise description of the problem.
According to this theory, weaknesses in phonological processing are not the only explanation for dyslexia. While many dyslexics do exhibit deficits in phonological awareness, there are also dyslexics who do not. In these cases, clinicians frequently observe weaknesses in rapid automatic naming (RAN). While there may be significant overlap between these two types of dyslexia, it is also possible for a child to show deficits in only one skill and not the other. The double deficit hypothesis provides a way to evaluate various degrees of dyslexia. On this view, the double deficit (phonological and RAN) underlies the most severe form of dyslexia. Less severe is the case of a child who has a deficit in phonological processing but not RAN. Finally, a child with normal phonological awareness, but a weakness in RAN, is described as having a mild case.
Recent developments in dyslexia research have led some to conclude that all previous models based on a single deficit are inadequate. One of the reasons for this is that dyslexia so often co-occurs with other cognitive disorders such as dysgraphia and dyscalculia, as well as more behavioral disorders like ADHD. Building on this observation, the multi-deficit model seeks to come up with a way of accounting for dyslexia in a way that takes these correlations into account.
This theory suggests that a wide range of cognitive skills underlie reading. Because of this, a reading difficulty like dyslexia emerges through a highly complex interaction between these. Dyslexia can arise due to weaknesses in phonological awareness, the various types of memory and even reasoning skills. In particular, working memory has received increasing attention as a skill that needs to be developed in order to treat dyslexia. All of these can contribute in a probabilistic way to a disorder like dyslexia. This means that their various contributions are subject to chance and other factors. This model has received criticism because it is difficult to test and falsify. But its insistence on treating dyslexia as a multi-faceted problem is probably the most realistic approach to the issue.
Can dyslexia go undetected?
Sometimes, specific learning disabilities like dyslexia can be hard to detect. Some children evade a diagnosis because they have exceptional abilities and can therefore mask their dyslexia.¹⁰ They feature in the literature as “twice exceptional” cases, because they are above average in ability and intelligence, while living with specific learning disabilities. Another common term is “stealth dyslexia”. Some signs of this include:
- Significant difference between verbal expression (high) and writing ability (low)
- Extremely illegible handwriting
- A tendency to “supply” words rather than reading what is actually on the page
Children in this category often under-achieve despite their high intelligence and sophisticated problem-solving abilities. If there is a substantial and unaccountable gap between your child’s ability and your child’s achievement at school, it might be unwise to rule out dyslexia as an underlying cause.
NEXT: Page 3: Diagnosing dyslexia