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What Is the Link Between ADHD and Working Memory?

Is distraction and hyperactivity unique to children with ADHD?

“Joseph was very articulate and our assessment with him took longer than usual as he asked questions frequently. He loves English and History and tried to begin many debates and discussions with us during the assessment. His mother says that he spends hours and hours researching topics that he finds interesting — these might not be related to school. However, his pattern of behavior on the Conners Rating Scale indicated a very high ADHD. When asked about his motivation levels, he was very apathetic and negative about his school and learning in general.”

Students with ADHD often have average or even high IQ. Yet they struggle with learning. I was quite puzzled by this for some time because usually high IQ scores are associated with good grades.

Then I noticed that another group of students displayed similar ADHD-type behaviors, such as fidgeting, being highly distractible, and lacking motivation.

How is it that students with ADHD and gifted students share similar IQ and behavior profiles, yet they have very different learning profiles?

The answer was in their working memory profile. The gifted students had excellent working memory, which was linked to their excellent grades. In contrast, the ADHD students’ poor working memory was linked to low achievement.

Average IQ does not always suggest average grades. If a student has a working memory problem, they can struggle academically even though they have average IQ ability.

The interesting thing about the working memory profile of a student with ADHD is that they do not have difficulties in short-term memory. In a testing situation, they can recall digits, words, instructions, and spatial locations at the same rate as their peers. In the classroom, they can usually remember what you have told them and repeat it back.

The problem arises when they actually have to manage or manipulate that information, in both verbal and visual domains. They struggle when they have to hold information in mind and use that to guide their behavior toward tasks or goals.

How reliable are these working memory deficits in students with ADHD? In order to answer this question, I looked at a range of executive function tests, such as inhibition, shifting, and planning actions, as well as working memory, to see which of these tests would be the best in identifying students with ADHD from their typically developing peers. Out of all the executive function and working memory tests, visual-spatial working memory was the test that was the best identifier of students with ADHD in the classroom.

This tells us that visual-spatial working memory deficits are such a prominent feature of students with ADHD and can be used as an additional diagnostic tool to identify them in the classroom.

Watch a video on the link between ADHD and working memory.

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