The Phonological Disorder Theory Janet Hatcher and Margaret J. Snowling
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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 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).
The word ‘dog’ can be broken down into three phonemes (the smallest units of sound, see graphic).
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 evidence).
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.
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.