Wednesday, 13 December 2017

Regression to the mean and IQ

People say that the offspring of high IQ individuals will regress to the mean (average) of their 'population' - and they calculate this as if it were a mathematical law...

But intelligence is a measure of a biological variable, and 'regression towards the mean' happens, if-and-when it does, for biological reasons - it is not a mathematical law.

When a high IQ individual is a descendant of high IQ parents, grandparents etc - there is no regression to the mean.

(Except for the trivial reason that test-takers who score highly because they 'have a good day' will re-test at lower scores. This can be somewhat dealt with by having several measurements of IQ - although this also increases the chance of 'having a bad day' maybe from non-random illness, and falsely dragging down the average. In practice there is no substitute for high quality data and increased numbers/ averageing does not help. This means excluding from the data any people who are suffering from acute, test-score suppressing illness or any other systematic cause for false measurement. In biology; smaller higher quality studies are always better than larger, poorer quality studies.)

In other words, to the extent that a high IQ individual comes from a genetically-relatively-intelligence-inbreeding caste or class; there is no regression to the mean.

And, in fact this is a very common situation - at least to the extent that regression to the mean is insignificant in amongst other factors. 

The point to hold in mind is that no variation/ distribution is really random; randomness is just an assumption, a model, which may be expedient for specific purposes - but is not a general truth; indeed randomness is usually a false model when it comes to biology.

In sum, human behaviour and ability cannot be explained by mathematical rules - at most such rules summarise a specific data set - which must then be evaluated in terms of scientific quality. We cannot explain unless or until we know something of causes. 


Unknown said...

I've been thinking a good amount about this. I think I'm a genius, but sometimes I think I'm not. I see life in a certain way, but I don't tell the world, I know it's isolated from society. It feels that at times I'm in love with the idea of genius, instead of it as a construct. The internet, people; they all say the same thing. I'm looking for that difference. Mr. Charlton, these blogs are interesting.



Bruce Charlton said...

There are people who are 'a genius' by their nature (ie high intelligence with the Endogenous personality) - which is most a matter of its being innate. But only a small proportion of these become known, or achieve a recognised breakthrough. Quite a lot of genuine breakthroughs are not, nowadays, recognised. How many people are aware that intravenous ketamine infusions are the biggest breakthrough in the treatment of severe depression for... 70 years? Yet the discovery dates from 2000, at latest, and was published in a high impact journal.