The Phonological Disorder Theory
Janet Hatcher and Margaret J. Snowling

Watch this video as an alternative to reading the page.

The phonological disorder theory suggests that dyslexia affects a person's ability to represent the smallest units of speech sound (phonemes). The fact that the majority of dyslexic people show problems with short term verbal memory adds a great deal of weight to this argument (see bottom of page for evidence).

However the phonological deficit is not an international effect. It is most prominent in languages with a great deal of irregularity of spelling, such as English.

What is a phonological disorder?

Good question! This theory claims dyslexic people have a phonological deficit. It hinders the ability to clearly represent the smallest units of speech sound.

Ok but what is a phonological representation?

It is our understanding of how speech sound works. It allows us to break words down into their smallest units of sound and build them back up again. Basically it’s all about how we understand, remember and reproduce speech sounds.

How does a phonological disorder affect a dyslexic person?

It is not fully understood how exactly dyslexic people are affected by the phonological deficit. The main idea is dyslexic people have less precise representations. This creates confusion when dealing with the smallest units of speech sound (phonemes).

For example:

The word ‘dog’ can be broken down into three phonemes (the smallest units of sound, see graphic).

phonological disorder example card 1

This is, of course, a three letter word made up of three phonemes.

However the word ‘read’ is a four letter word that only has three phonemes (see graphic).


The theory argues that because dyslexic people’s phonological representations are less specified confusion occurs when dealing with the phonemes (see bottom of page for evidence).

Click here for phonics help.

Short term verbal memory:

Poor short term verbal memory is a very common cognitive difficulty for dyslexic people. We use verbal memory to blend sounds in words together when reading them for the first time. This is why an inability to read non-words (made up words) is one of the strongest signs of phonological dyslexia.

Problems with short term verbal memory naturally lead to difficulties with long term verbal memory. For example dyslexics may often forget the names of people they have met before.

More information:

If you want to learn more about the phonological theory click here for Margaret J. Snowling's book 'Dyslexia'.


The phonological disorder theory is generally the most popular explanation of dyslexia. It ties up most of the unusual symptoms that are seemingly not related to reading.

The fact that the majority of dyslexic people have problems with verbal short term memory adds weight to the argument. With a language with lots of irregular spellings having a good short term verbal memory must be fundamentally important.

However the fact that the phonological disorder is not a worldwide effect is a fundamental flaw. It is most recognizable in languages which use more irregular letter to sound combinations, such as English.

The main point is dyslexic people struggle to work with the smallest units of speech sound. However there is still the larger and more important question of why? Click here to find out about more possible causes of dyslexia.

Return from The Phonological Disorder Theory to Home Page.

Evidence for The Phonological Theory:

Phonological processing skills and deficits in adult dyslexics .

Developmental dyslexia: the role of phonological processing for the development of literacy.

Naming speed, phonological awareness, and orthographic knowledge in second graders.

Towards a further characterization of phonological and literacy problems in Dutch-speaking children with dyslexia.

Working memory deficit in dyslexia: behavioral and FMRI evidence.

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