mrsmith wrote:

That would correspond to 15% of the population, which much really be far to high, so it must be some additional filtering going on?

The only prevalence numbers I have seen are 2-3%, which corresponds to 2 stdevs.

No, 15 points for 1 SD doesn't mean 15% of the population. The way that a standard normal curve works is that ~68% of people lie within +/- 1 SD of the mean (in this case, 100). And 96% of people lie within +/- 2 SDs of the mean. So, only 2% of the population have an IQ of 130 or above (+2 SDs), and only 2% of the population have an IQ below 85 (-2 SDs).

It also isn't true that having greater than or equal to 1 SD between your VIQ and PIQ scores is equivalent to having a PIQ score that is greater than or equal to 1 SD below the mean. As I showed above, my PIQ is 1 SD

**above** the mean, but I still have NVLD, due to its relationship to my VIQ score. Now, I'm sure that most NVLD-ers out there do have a PIQ in the 80-90 range; I realize that I am not a typical case. (I am fortunate enough to have taught myself certain visual-spatial skills over the years.) But again, it is possible to have NVLD with any level PIQ score, so long as it is 15+ points lower than the VIQ score.

As far as prevalence rates of NVLD, what I commonly read is that NVLD makes up around 1-10% of all total learning disorders. It's not all that common, even in the learning disorder category, but again, that statistic doesn't refer to specific IQ scores.

And in response to Ravenclawgurl, Symbol Coding/Processing Speed is only one component of PIQ. Block Design, Matrices, and other tests also are factored in for PIQ. Having low Processing Speed doesn't necessarily mean NVLD. I scored extremely highly in Processing Speed, yet I have NVLD.

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