Does dyslexia affect working memory?

People often ask about working memory when a child or adult seems to understand an idea but loses track of several spoken steps, finds it difficult to hold sounds in mind while spelling, or struggles to listen and write at the same time.

Research suggests that some children with dyslexia find certain working-memory tasks more demanding than comparison groups, especially tasks involving spoken words, digits or speech sounds. However, this is not true for everyone with dyslexia, and a working-memory assessment cannot diagnose dyslexia on its own.

Most research in this area has involved children, so the same patterns should not automatically be assumed in adults with dyslexia.

What do short-term memory and working memory mean?

Short-term memory is the ability to hold information briefly. For example, this might involve remembering a short sequence of digits long enough to repeat it.

Working memory involves holding information in mind while using it. A task might require someone to remember a sequence of sounds while blending them into a word, or to retain part of a sentence while considering its meaning.

Researchers assess different forms of working memory. Verbal working memory involves spoken information, including words, digits and speech sounds. The part concerned with briefly holding speech-based information is sometimes called the phonological loop. Visuospatial working memory involves visual information, such as shapes, patterns or locations.

These terms describe the kinds of information used in a task. They do not describe fixed categories of learners: reading and spelling tasks can involve several skills at once, including knowledge of language and the sound structure of words.

What does the research suggest?

Research with children with dyslexia has identified average differences on verbal and visuospatial working-memory tasks when compared with children without dyslexia. The clearest pattern is for verbal working memory: tasks involving speech sounds, words, digit sequences, or verbal information that must be held while it is used.

Research involving broader groups of children with reading difficulties points in a similar direction. On average, these groups have found short-term-memory and working-memory tasks more difficult than comparison groups, particularly tasks requiring the recall of phonemes or digit sequences and tasks that combine remembering verbal information with another mental step.

This does not mean that dyslexia is caused by working-memory difficulty. The available research cannot establish whether these differences are a cause, consequence or associated feature of reading difficulties. Working-memory tasks can also draw on language skills, attention and the particular demands of the task.

The findings are best understood as describing a pattern seen across groups of children, not a rule about any individual child. Some children with dyslexia may have clear difficulties on working-memory tasks; others may not.

Why are speech sounds especially relevant?

Dyslexia is associated with difficulties in aspects of phonological processing: noticing and working with the speech sounds in words. This makes verbally based memory tasks particularly relevant, because they may ask a child to retain and work with those sounds at the same time.

For example, a task may ask a child to repeat digits backwards, hold individual sounds in mind while blending them into a word, or remember information from a spoken sentence. Across the research, the differences reported on tasks of this kind have generally been larger than those reported on visuospatial working-memory tasks.

This should not be used to interpret everyday experiences too quickly. Forgetting an instruction, for example, does not establish dyslexia or a working-memory difficulty. The instruction may have been lengthy, unfamiliar or delivered quickly, and many factors can affect how someone responds on a particular occasion.

It can nevertheless be useful to consider how information is presented. A multi-step spoken instruction asks a learner to retain earlier steps while listening to later ones. A written task may ask a learner to hold sounds in mind while deciding how to spell an unfamiliar word. These are examples of situations that can place demands on verbal working memory; they do not show why a particular learner finds the task difficult.

What about visual and spatial working memory?

The evidence for visual and spatial working memory is less consistent. Research with children with dyslexia has reported average differences on visuospatial tasks, but these have generally been smaller than the differences seen on verbal tasks.

There is also evidence that broader difficulties with managing attention, responses and behaviour are not inevitable in dyslexia. In a UK cohort, children with dyslexia without developmental language disorder showed a similar pattern to comparison children on a broad measure that included a visuospatial-memory task. This does not rule out visuospatial working-memory difficulty in individual children with dyslexia, but it supports caution about treating it as a standard feature of dyslexia.

Different studies use different tasks, definitions and participant groups. Some tasks described as working-memory measures also involve other skills. For that reason, it is more accurate to say that visual and spatial working memory may be relevant for some children with dyslexia than to assume a visual-memory difficulty is present.

Can working memory be used to identify dyslexia?

No. Working-memory difficulty is not required for a diagnosis of dyslexia, and it is not unique to dyslexia. A person may find working-memory tasks difficult for a range of reasons, and someone with dyslexia may not show a clear difficulty on those tasks.

Assessment for dyslexia needs to consider literacy skills, language-related skills, learning history and the person’s individual profile. A memory task can provide useful information about how someone approached a particular assessment, but it cannot confirm or rule out dyslexia in isolation.

This is also why broad statements such as “people with dyslexia have poor memory” are inaccurate. The research points to differences on particular tasks, especially those involving verbal information. It does not show that everyone with dyslexia has difficulty remembering information in general.

Reducing unnecessary memory demands

Where spoken information or multi-step tasks are difficult to manage, a practical approach is to reduce the amount that needs to be held in mind at once. This may be useful whether or not a learner has a formal diagnosis.

Possible approaches include:

• giving instructions in shorter stages;

• providing key steps in writing;

• demonstrating a task as well as explaining it aloud;

• using a checklist for a task with several stages;

• allowing time to check what needs to be done before beginning;

• sharing an agenda or key points before a meeting, lesson or discussion.

These approaches do not identify the reason for a difficulty, nor are they a replacement for a careful assessment where one is needed. They can simply make it easier to keep track of the information required for a task.

So, does dyslexia affect working memory?

For some children, yes. Research suggests that children with dyslexia are more likely than comparison groups to find some working-memory tasks demanding, particularly tasks involving spoken information and speech sounds. Differences in visual and spatial working memory have also been reported, but the evidence is less consistent and the differences are generally smaller.

Working-memory difficulty is neither universal nor diagnostic of dyslexia. The most helpful response is to identify which tasks create the greatest memory demands for the individual and to consider whether information could be presented in a clearer, more manageable way.