Types of dyslexia: definition, symptoms and causes

Dyslexia is the most common disorder when it comes to learning disabilities. It is particularly detected in school and affects the reading processes, which end up affecting and hampering the writing processes.

In this article, we will know the three types of dyslexia according to the affected reading path., And the two types of dyslexia according to their origin. We will analyze the characteristics of each of them and see the differences they present, as well as their symptoms.

Types of dyslexia

Dyslexia is a learning disability characterized by difficulty reading correctly. This difficulty manifests itself in symptoms such as exchanging letters when reading, confusion and / or omitting words when reading. In addition, it can (and often) cause writing difficulties.

It is a very common disorder in children and adolescents (especially in children). More precisely, it represents 80% of cases of learning disabilities. It is estimated that its prevalence is between 2 and 8% of children in school.

however, there are different types of dyslexia. We can classify them according to various parameters. We will focus on two: according to the affected read path and according to the origin. But first, let’s see what is meant by reading paths through the two-track theory.

Dual Path Theory

When we learn to read, we can do it through several ways of reading: the direct or visual way and the indirect or phonological way. These two paths are the concepts posed by the theory of the double path of reading.

To understand the different types of dyslexia that exist depending on the affected pathway, one must first understand how each of the possible reading pathways works, because depending on which pathway or another is affected, the type of dyslexia will be. either.

1. By visual

The visual route is also called the direct route or the lexical route.. When we use this path, we look at the graphical representation of words and relate it to their meanings. As the name suggests, it’s a sight-centric pathway, and it makes us read the words “globally”, without spelling letter by letter.

In this way, we go from words (through a gestalt and a global perception of them) to the meaning of the term, then to its pronunciation (we read).

2. Phonological path

This second path is also called the indirect or sequential path.; when we use it in reading, we focus on the sounds of the letters to transform them into words, through a process of grapheme-to-phoneme conversion.

In other words, we are based on the use of a phonemic coding, letter by letter spelling, sound by sound, we have to form the word. This is why it is also called sequential or indirect.

Unlike the visual path, the mechanism of the phonological path is to access the word, to decode it from phoneme to grapheme, to pronounce it and finally to access its meaning.

Depending on the route concerned

The first parameter or criterion that we will use to classify the different types of dyslexia is according to the affected pathway. Thus, as we have announced, depending on whether the lexical or phonological pathways or both are affected, there are three types of dyslexia:

1. Lexical dyslexia

The first of the types of dyslexia is lexical dyslexia, where the affected pathway is the lexical pathway.. Always remember that the name dyslexia corresponds to the affected pathway. This type of dyslexia is also called superficial dyslexia.

A subject presenting it will have difficulty reading irregular words; that is, “atypical” words, with special writing rules, which deviate from the usual pattern (like irregular verbs).

This dyslexia is also called perceptual-visual dyslexia because the visual pathway is affected. What happens in this type of dyslexia is that the person, not being able to read globally, because they have the affected visual path, must read letter by letter, decoding the phoneme-grapheme.

Other associated symptoms

In addition, lexical dyslexia usually appears at age 7 or 8 (unlike others that appear later). It is also accompanied by deficits in psychomotor abilities and immediate memory (which allows us to remember events that have just occurred). The person confuses letters when reading, exhibits reading comprehension problems, and has impaired writing (writing with inversions).

Finally, another characteristic symptom is the impairment of perceptual-visual skills when solving visual problems or locating objects.

2. Phonological dyslexia

The second of the types of dyslexia depending on the pathway affected is phonological dyslexia, in which the phonological pathway (Not lexical, indirect or sequential) is affected. The main difficulties are, in this case, the reading of pseudo-words (that is to say words which do not exist, invented).

This is explained as follows: the person who suffers from it, not being able to read letter by letter accessing the meaning of the words, because he has the phonological path affected, it is necessary to try the visual or direct path. And, not being able to decode the phoneme-grapheme, you will have difficulty reading words which do not really exist, because you will have to read them globally, and since they do not exist (and you are not used to them), here be the difficulty of dealing with them.

Other associated symptoms

This type of dyslexia is also called auditory-linguistic dyslexia. It usually appears later than the previous one, in children between 9 and 12 years old. The alterations that accompany it are linked to immediate auditory memory. In addition, the person confuses words that sound similar and skips letters when reading (omits them).

On the other hand, as in visual dyslexia, the subject presents writing changes, syntactic errors, as well as poor reading comprehension.

3. Profound dyslexia

The last of the types of dyslexia is deep dyslexia, the most severe. It is also called mixed dyslexia because both pathways are affected; the visual and the phonological. More precisely, however, the most affected is the phonological path (which cannot be used at all); on the contrary, the visual path is partially preserved, which is why the subject is the only one able to use it (in part).

In this case, the subject has difficulty reading all the words, whether they are regular, irregular or pseudo-words. This is why reading comprehension in this case is zero.

According to the origin

The second criterion that we will use to classify the different types of dyslexia is according to their origin. So, we find two types of dyslexia, we know them below.

1. Progressive dyslexia

This dyslexia is also called developmental dyslexia. Its origin is unknown, but it has been linked to genetic alterations and delayed maturation. It affects from birth; however, it can obviously begin to be detected when the boy or girl begins to learn to read. It is more common than the following type of dyslexia (acquired dyslexia).

2. Acquired dyslexia

In that case, acquired dyslexia has its origin in a brain injury that affects one or more areas of the brain involved in the literacy process. Depending on the child’s age at the time of the injury, their brain plasticity, the cognitive stimulation they receive later and other variables, the dyslexia that will appear will be more or less severe, and more or less. less temporary.

Bibliographical references:

  • American Psychiatric Association -APA- (2014). DSM-5. Diagnostic and Statistical Manual of Mental Disorders. Madrid: Panamericana.

  • Andalusian Association of Dyslexia (Asandis). (2010). General guide to dyslexia.

  • Tamayo, S. (2017). Dyslexia and difficulties in acquiring literacy. Teacher, Journal of Curriculum and Teacher Training, 21 (1): 423-432.

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