Beliavsky wrote:
On Nov 13, 8:22 am, Ericka Kammerer wrote:

Families living in poverty, or even close to it, have been excluded.
The parents in my sample also stayed together for at least the first
seven years of the younger sibling's life.
Again, skewing the sample based on assuming the
anticipated results hold true. You're supposed to *test*
these things, not build them into your research design..

The second exclusion makes sense to me, because parents divorcing
changes the environment for the children, and Murray is trying to
control for environment.

But it introduces a confound in that IQ and divorce
may be related. One should at least include and run the
tests and report any differences and the degree of confounding,
if any.

How much difference did IQ make? Earned income is a good place to
begin. In 1993, when we took our most recent look at them, members of
the sample were aged 28-36. That year, the bright siblings earned
almost double the average of the dull: £22,400 compared to £11,800.
The normals were in the middle, averaging £16,800.
And did they take birth order into effect? Quite a
few studies now seem to show sizeable birth order effects
on earnings, type of occupation, and risk tolerance (along
with small IQ differences). Clearly a confound, and one
that might explain a decent chunk of the results independently
of IQ.
Put together birth order issues and the odds that
a child with normal or above IQ parents and siblings would
have low IQ without any other disability that might also
affect earnings or success, and you've got some holes you
could drive a truck through.

I don't know of evidence that birth-order effects are nearly as large
as the IQ effects Murray found, and one economist found that the
effect "makes essentially no difference" (see below). In general, many
critics of IQ researchers dislike the conclusions of the research, so
they magnify, deliberately or not, the importance of any
methodological defects they perceive. I think that is what you and
toto have done.

I don't think you can handwave away methodolgical
issues quite so easily. There are a lot of people with
agendas out there doing research, and there's a lot of
poor quality research. Careful review of methodology and
good literature reviews are the only thing that stand
between acting on poor quality information and high quality
information.
No one is arguing that IQ is irrelevant, but you
have posted some very poor quality (not to mention
controversial) studies to support exaggerated claims of
IQ being the driving force behind success by a variety of
measures. I, for one, would not bet the farm on those
predictions. I have some very high IQ kids. There is
no guarantee that they will be successful or productive
just because they're smart. In fact, among their high
IQ schoolmates, there are obvious examples of underachievers
and students with poor work habits who may well struggle
if they don't shape up. Studies of gifted kids are replete
with examples of underachievers and even miserable failures
(if you define success as being a productive member of
society able to support one's self and one's family).
Heck, I've got a whole branch of the more distant family who
are shining examples of highly intelligent folks who
are failures according to just about any measure. The
infamous Terman study of the highly gifted found nowhere
near the proportion of highly successful folks they
initially expected to find. Slice it any way you like,
and it's clear that at some point, IQ is an advantage,
but it's nowhere near determinative of success or happiness.
So, when one puts on one's parental hat (this is, after
all, a parenting newsgroup) and asks what
factors one needs to influence in order to provide
children with the best start in life, coughing up some
high-IQ gametes just isn't anywhere near enough.

http://econlog.econlib.org/archives/...rth_order.html
The Birth Order Illusion
Bryan Caplan

However, if you regress real income on birth order AND family size,
you get a totally different picture. Birth order makes essentially no
difference (in fact, the sign reverses), but average income falls by
about $2400/child in your family. First-born only child? You'll make
more than average. First-child child in a big family? You'll do no
better than the fifth-born child - maybe a little worse!

Does this show that big families hurt incomes? Possibly, but the
simpler story is more plausible: Poor people have more kids, and kids
of poor people tend to be poor themselves.

If you look a little more, you will find many studies
that *do* show a birth order effect, even after controlling
for family size. You'll also find some studies that show
no effect for either factor, and some that show a birth
order effect with no family size effect. If you look at
what is said by those who follow the literature, most seem
to be placing their bets on birth order having some
significant effect in addition to other likely factors.

Best wishes,
Ericka