Anyone know what is the percent of 2E kids in the normal population? And specifically the percent of HG+ kids that also have a LD?

If for example, a kid with iq >160 occurs 1:10,000 to 100,000 what's the incidence of a kid that's 2E with iq>160 like 1:1,000,000???

Review article on 2e from NAGC researchers, which estimates prevalence as ~300,000 in the USA:

http://maxwellgate.pbworks.com/w/fi...calInvestigationTwice-Exceptionality.pdf

Same information, in an NAGC white paper:

https://www.nagc.org/sites/default/files/Position%20Statement/twice%20exceptional.pdf

I've also seen 2-5%. The research is not particularly clear, as investigators use different definitions of both categories of exceptionality.

More recent research, looking at the % of disabled children who were assessed at 120+ (90+ %ile) on at least one WJIII achievement measure. They came up with 9% of disabled students:

http://masseyuniversity.mrooms.net/...a%20Special%20Education%20Population.pdf

There is some evidence that ADHD is evenly distributed across the cognition bell curve, and that LD is not (the previous citation references 36% of LD students potentially identifiable as gifted--keeping in mind that most standard definitions of LD rule out everyone below average a priori, so you're starting the discussion from only the upper half of the population).

In HG+ kids, even less is known.

This is an interesting local effort to identify 2e learners, which focused on already identified GT students (90+%ile), and found about 15-20% of them were 2e. It also includes what they did to try to remediate the other exceptionality.

http://www.stthomas.edu/media/project2excel/pdf/RevisedCombinedP2XAdminstratorUpdate2011.pdf

Thank you
The articles were very helpful. Sheds some light on this mystery of 2e kids.

I don't have a lot of stats, but probabilities for 2E and high IQ wouldn't multiply like that (going from 1e4 to 1e6). The two components are highly correlated, so mathematically, their probabilities would be of similar order. The correlation grows starting at around IQ of 125 and reaches almost 0.9 at 160, meaning that majority of the HG+ individuals are not neurotypical, but it could be very minor.

I'll find the references and post it.

Wow! .9 correlation at iq>160?

That means people at extremely high IQs, the brain has a hard time balancing high functioning in all general areas, and actually starts depleting some parts of the cortex. The brain is essentially at full capacity and must balance this by having weak areas resulting in SLDs, ASP, and ADHD, dyslexia etc.

So around 140-150 iq, less 2E occurrences because the brain isn't at full capacity and can balance effectively? So therefore, the more average iq a person has the more well rounded they can essentially be, but not necessarily especially great at one thing?

I wouldn't leap to that conclusion. While I don't know the reason for this high correlation, one might speculate that
a) Exceptionally gifted individuals have brains that are somehow physiologically different from neurotypicals. This might mean that the brain is wired to do certain things really well but other things not so well. (e.g. a sports car vs. a hybrid vs. a tow truck when considering speed, gas mileage, and brute power)
b) Brains are remarkably plastic, especially in childhood. It's possible that some extremely gifted individuals focused on building certain skills to the detrimental neglect of others. This may be neither inevitable nor permanent but would require work to remedy (e.g. OT, PT etc; or earlier just guiding the child to spend time developing skills that don't interest them as much).

Both a) and b) might be completely wrong, but I wouldn't leap to conclusions without solid research. Also fwiw my understanding is that from fMRI studies etc we appear to use our brains far below their full capacity.

So I'm jumping in with no expertise of any kind here, but a lot of the language above really strikes me: weakness, detrimental neglect, depleting.... Two thoughts strike me.

1) Most LDs are not "weaknesses", evolutionarily speaking. Reading and writing, for instance, are recent inventions, and only even more recently have they become common expectations for all people. What is actually surprising is that so many people have brains designed to be able to automatically do functions which have no evolutionary use, let alone advantage. So most common LDs are only weaknesses in the construct of living in this exact moment of time and geography. And the biggest ones, in reading and writing, are severely exacerbated by the idiosyncrasies of the extremely illogical way we have developed the English alphabet and spelling (it's dramatically less debilitating to be dyslexic in Spanish). Even ADHD has some notable advantages - if you are not living in a modern, sit-quiet-at-a-desk-all-day-long-and-comply-society.

2) Now here I am just totally speculating, but the more I research, the more it seems to me that the more brains differ from the norm in one respect, the more they are likely to differ in numerous respects. It's not just one single function (that which we measure as IQ) that is different while everything else stays exactly the same. Rather, it all feels to me like the further one is from the norm, the more that brain simply functions differently from the norm in an increasing numbers of ways. The more intense thinking is part of a package of more intense feeling and sensitivity to what is experienced, resulting in some people truly experiencing the world in a qualitatively (and not just quantitatively) different way than most. Asynchrony, overexcitabilities, sensory issues, ASD might all be aspects of brains that just function differently from the norm. And these different and intense ways of experiencing the world may be part of what enables the different thinking, rather than a detrimental cost of it.

No proof of any of this, of course, but it's a different way of thinking about 2E. I personally find it helpful to recognize just how absolutely unnatural and discordant, evolutionarily speaking, modern school expectations are - for behaviour as well as functioning - for a significant portion of the human race. Instead of asking "Why can't my kids do this?", it's interesting to contemplate the question "Why should we ever expect any group of children to all be able to do this?"

I think very similarly to Platypus101 - school is an artificial construct. We are trying to teach to one type of student, which is an average that doesn't really exist in real life- it just hopefully works for the majority of kids.

I tend to think of my children as wired tighter than NT kids, and so all sorts of stuff comes with that. I tend to think in terms of "is their giftedness working for them or against them" rather than 2e specifically. For the kids where their brain configurations are working very efficiently in a particular way, they may be better adapted to the artificial constructs of modern society. For other gifted kids, their brains may measure similarly on an iq scale, but might be better adapted for a different type of developmental model in which adhd or other things we consider to be deficits are actually assets.

I think in the case of some disabilities, this is probably the case. My DD with ADHD doesn't filter anything out. She would do great as a caveman watching out for wooly mammoth to hunt. Not so great sitting in school when 30 kids are surrounding her talking and she's expected to figure out 982 divided by 36.

DS, on the other hand, would be dead as a caveman, with his coordination issues, he probably would have been eaten by a wooly mammoth. He doesn't function all that well in modern society either, the challenges are just different.

Spit-take! My DD doesn't have ADHD but she doesn't miss anything, either. Wound up tight and would imagine wooly mammoth if there weren't a real one around to scare her into flight!

DS would be a dead-caveman, too. Not because of coordination challenges, but because he wouldn't notice he was being eaten until he was half-digested.

The concept of the human brain not working at the full capacity is a little outdated. The fMRI studies show that the brain uses everything it has. Evolutionary speaking, your body won't feed cells that it doesn't use and the immune system will reabsorb them. The brain is the second consumer of glucose in the body (after the heart), so having a brain and not using it is very wasteful and unacceptable in evolutionary biology.

So the co-morbidity between different neurological disorders and high IQ doesn't stem from how we use the brain, but from the structural differences in the neural network.

For example... In the last ten years, using tools like fMRI, it is been established that the higher IQ individuals follow a different curve when it comes to cortical thickening and thinning. It looks like the higher the IQ, the longer the brain spends first over-connecting, reaching the peak much later in the childhood - around 13-14, instead of 7-8. After that it thins out almost or even faster than in typical children.

Now if it look at disorders such as autism, ADHD and schizophrenia, the research also points to a differentiated process of cortical thickening and thinning. In ASD individuals, the brain is often much larger than in normal children, showing signs of overconnectivity and lack of normal neural pruning - immune system function that targets neural connections that are unused, unneeded etc. As the brain prunes itself, the understanding becomes more streamlined, the speech becomes less garbled, the attention span gets longer etc... In the absence of it - sensory overload, speech delays and inability to understand and execute instructions well, typical in ASD. ADHD also shows a delay in cortical thinning when the children reach the peak, but at a later age, basically following a similar trajectory as the high IQ individuals. Some research into schizophrenia shows that the hallmark symptom - hallucinations - may come from unpruned connections, where the brain can self-generate stimuli that doesn't exist or use older memories as the new input.

So the same presentation - overconnected brain - can either result in out-of-box thinking, creativity and ability to see what others can't or in difficulty understanding human language and sensory overstimulation. Or both.

It looks like the bigger the brain capacity/connectivity, the easier it is for the brain to fall into a less typical developmental trajectory, with various symptoms and abnormalities - hence a high correlation between learning disabilities and high IQ.

I have some saved links about this--it's so interesting. The first one is about cortical thickness and IQ, the second is about ADHD, third ASD.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3985090/

http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0035770

http://brain.oxfordjournals.org/content/137/6/1799

When DS was in process of being evaluated for ASD, I kept finding anecdotal information about "big heads" being associated with ASD. That seemed ridiculous, but I guess it's actually true, frequently! DS head was so big he had a CT scan (age 6 months) to make sure he didn't have hydrocephalus. He is now starting to grow into his head.

A child at the age of 3 has more neural connections than an adult, even though the brain volume is smaller. As the child grows up, synaptic or neural pruning occurs and the child loses most of his childhood memories but begins to think more rationally or more clearly.
https://en.m.wikipedia.org/wiki/Synaptic_pruning

A more intelligent brain spends more time over connecting...
http://www.nimh.nih.gov/news/science-news/2006/cortex-matures-faster-in-youth-with-highest-iq.shtml

An ASD individual may have more connections than typically developing children
http://www.medscape.com/viewarticle/830316
http://newsroom.cumc.columbia.edu/blog/2014/08/21/children-autism-extra-synapses-brain/

Schizophrenia is linked to abnormal pruning as well:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3104582/

Eco21268 posted a good reference on ADHD (thanks!), but unfortunaltely the authors didn't look at the dynamics of the cortical thickness and it is the key for high IQ kids and ADHD.... Measuring it at only one point in time is misleading.

Bipolar/mood disorder...
http://www.ncbi.nlm.nih.gov/m/pubmed/11986993/

Thanks Chicagomom - real info much appreciated!

And eco - - - your younger DS is starting to sound MUCH too familiar. Half-digested indeed.

Differentiation in synaptic pruning is just an example of things that correlate with mental disabilities just as well as they correlate with higher cognition...

There are two more things that easily come to mind:

1) Testosterone levels, specifically fetal testosterone. Apparently when it is high your child will have much better visual spatial abilities and general intelligence
http://www.sciencedirect.com/science/article/pii/S1041608009001083
https://www.sciencedaily.com/releases/2011/03/110311153549.htm

and, just as likely, your child will have ASD traits and introversion.
http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.471.4530&rep=rep1&type=pdf

2) Mitochondrial DNA variants. Mitochondria is a symbiotic organism that's been living with us for millions of years, but it isn't human - it has its own DNA. Its basic role is to provide energy to the cells, including the brain. It is been hypothesized that the brain neural efficiency is directly related to the mitochondrial health and its ability to metabolize glucose into ATP.

Some are associated with higher IQ
http://www.davidsongifted.org/db/Articles_id_10032.aspx
some are associated with schizophrenia and ASD:
http://www.ncbi.nlm.nih.gov/pubmed/25446950
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3285768/
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0127280
and with attention issues:
http://scholarworks.gsu.edu/cgi/viewcontent.cgi?article=1082&context=psych_theses

Since each cell has 1000-2000 of these, you have millions of cells, and each can have its own slightly-different DNA mutations, you really can get any combination you want, different cells working differently, atypical development etc. Unlike the nuclear human DNA, it isn't long - only 37 genes, so they are multi-tasking. One mutates and you have a myriad of issues. Luckily for us, they don't mutate at the same time in all of the cells....

These two specifically are passed maternally - one through prenatal exposure and one through the egg.