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*.

https://charltonteaching.blogspot.co.uk/2010/10/scope-and-nature-of-epidemiology.html

https://charltonteaching.blogspot.co.uk/2008/05/social-class-iq-differences-and.html