What Is the Best IQ Test to Test "How High" an Adult's IQ is?

I am a high intelligence specialist and I have a background in test & measurement and am currently working on normative sampling for updated IQ tests here in the US.

Here's my opinion on why it is very difficult - if not impossible - to develop an IQ test for the smartest adults: Once people are adults, experience, exposure (opportunity), education, and ability to focus on mastering something become inextricably intertwined with pure intellectual factors and comparisons become less about relative intelligence and more about who wishes to study for or "game" a test.

My own work has focused on discerning levels and profiles of intelligence in the very young, children six and under, because interests and developmental milestones are still largely un-tampered with (relatively speaking) and as most parents know, it is difficult to teach something to a very young child if the child isn't interested;-) What we discover by looking at these early interests and developmental milestones is that we can indeed estimate where a child will eventually test on the intellectual continuum (IQ range) and what this child is likely to need at school, at home, and in social and emotional relationships and interactions in order to thrive, be emotionally healthy, and end up being nicely productive and happy.

This early "diagnosis" of high intelligence doesn't necessarily translate into adult success or degrees or credentials, but the underlying factors remain and most people who know such an adult realize the person is phenomenally smart even though (perhaps) unsuccessful or a failure in common terms. Early diagnoses that don't result in proper support (at home, at school, within social circles) can still doom a highly intelligent child to a very unsatisfying and unproductive life despite any innate intelligence he or she might possess.

So, the perfect high IQ test for high ability adults? I don't think there is or can be such a thing until we simply can connect electrodes or fMRIs to somehow assess purely how one brain functions compared to another. And, I ask, why is this so important really? If the diagnosis isn't to help with better understanding what a person is capable of learning, how a person manages social adjustment, finding friends, etc., then why is it an important thing to measure? I'm open to hearing good answers that I may not have considered.

Since it does run in families, you can do what so many of us in this field have done: find out how smart your own biological children or grandchildren are (get them tested or fill out the online Ruf Estimates Kids IQ Test on this website) and make a good estimate from that. If you have a phenomenally intelligent child, you're likely to be at least moderately gifted and probably highly gifted yourself. If you do look at my 5 Levels of Giftedness materials, you can pretty much assume that you are within one level higher or lower than your children or the average of your children. One family can have a range of about three levels and still be completely normal. But it simply isn't likely that you could have a Level Four child and not be at least a Level 2 intellect yourself. So interesting.

Personally, I think the most important reason to know any of this is to find out if you are too different or unusual for some of the people you're trying to please, work with, get along with. If they don't get your jokes, it may not be because something is wrong with you;-)