Reading difficulties and ADHD often co-occur. Learning to read requires sustained attention on activities that may not interest kids with ADHD. Contrary to popular thinking, learning to read is hard. Learning any new skill is hard and reading is no exception. However, once kids with ADHD know how to read, they can flourish. Their inattention may even be advantageous in some situations, that is, if they have some form of intellectual inattention, in which they constantly seek stimulation through encountering new ideas in books.
In this post, I’m going to answer some probability questions in regards to reading. What is the the probability that a kid has:
a) either dyslexia or ADHD or both?
b) either dyslexia or ADHD, but not both?
c) doesn’t have dyslexia or ADHD?
How common is dyslexia?
According to neuroscientist Stanislaus Dehaene, about 5-17% of kids have dyslexia. Some dyslexia businesses claim that 30% of kids have dyslexia. I think 30% is an absurdly high estimation, given the much more prevalent frequency of instructional failure. Just because a child struggles to learn to read, does not mean that child has dyslexia. Very few schools use research-based instruction with explicit, systematic phonics and decodable texts. Therefore, many, many smart kids without dyslexia still struggle with learning how to read.
I learned how to teach reading from John Shefelbine. According to him, only 5% of kids have dyslexia–these are the kids that learn to read at a much, much slower rate than their peers even when given research-based instruction.
In this post, I’m going to use Dehaene’s estimate of 5-17% and take the average–11%–to figure out the questions above. That is, in the calculations in this post, I’m assuming 11% of kids have dyslexia. However, it should be clear by now that we don’t know the exact frequency of dyslexia.
How common is ADHD?
About 10% of kids have ADHD. According to researcher Dr. Philip Shaw, ADHD occurs all throughout the world and has been around from the very inception of our species. There have always been hyper, impulsive kids in every society. As stated in our last post, ADHD is real. ADHD shows up on brain scans and is highly heritable. ADHD seriously impacts the learning how to read process, as kids with ADHD struggle to avoid otherwise mundane distractions in our everyday world. As an educator, you may find that your students with ADHD jump, spin, and talk excessively during reading time.
How many kids have ADHD and dyslexia?
Dyslexia and ADHD often co-occur. Kids with ADHD learn to compensate for their impulsivity. Therefore, they begin to use the same crutches as kids with dyslexia–looking at pictures, guessing based on the first letter, and predicting what word comes next. They develop the same coping mechanisms.
About 2.5% of kids have ADHD and dyslexia.
Now, let’s get back to our probability questions above…
What is the the probability that a kid has either dyslexia or ADHD or both?
In this case, we can use the General Addition Rule in statistics:
P(A or B)= P(A) + P(B) – P(A and B)
.11 + .1 – .025 = .185
Then, you move the decimal to get 18.5 %.
That is, 18.5% of kids have dyslexia or ADHD or both. This, of course, is an estimation. I outlined the numbers I used above.
What is the the probability that a kid has either dyslexia or ADHD, but not both?
With this questions, you take the number you found above–.185–and use it in the equation.
P(A or B, but not both) = P(A or B) – P(A and B)
.185 – .025 = .16
This means, 16% of kids have dyslexia or ADHD, but not both.
What is the the probability that a kid doesn’t have either dyslexia or ADHD?
Here you can use the Complement Rule in statistics.
P(Ac) = 1- P(A)
1- .185 = .815
This means, 81.5% of kids don’t have dyslexia or ADHD.
The rate of instructional failure is very high.
Very few schools use research-based instruction. Therefore, reading problems can develop simply because a student needs access to explicit, phonics instruction. Some kids are almost immune to poor reading instruction and will learn to read with nearly any curriculum. However, there’s a large subset of kids–and these are smart kids–that require explicit, phonics-based instruction, even when dyslexia or ADHD is not present.
If we give students research-based instruction, the rates of reading difficulties will drop precipitously.