Category: Science

So if we could get people to exercise more, would they become more risk-loving, want less insurance, make more aggressive investments, and induce faster economic growth?  Would this be a good thing?

That’s Robin Hanson, the basic empirical result is that physically weaker people are more risk-averse in a wide variety of settings.

People exhibit less prejudice when they’re in the presence of a mirror, Dutch researchers have shown. Carina Wiekens
and Diederik Stapel said this effect occurs because mirrors make us
more aware of our public appearance, and therefore remind us of the
need to fall in line with social norms.

Here is more.  Perhaps I have seen too many vampire movies, but in general I am of the opinion that mirrors have a real influence on our behavior.

A man who knows he has this allele, she added, might be able to use the
knowledge to ignore tugs of restlessness he might feel in his marriage:
"You can say, ‘Oh, it is just my DNA, and I am going to ignore it.’ "

…Fisher [an academic researcher], who described herself as a romantic, said she would not reject
a potential mate who has two copies of the risky allele. She paused,
then added: "But I might not start a joint bank account with them for
the first few years."

Here is the full story.  Maybe they should put that on a T-shirt: "Oh, it is just my DNA, and I am going to ignore it."

Here are some recent results, from Sandra Black, Paul Devereux, and Kjell Salvanes.

More able parents tend to have more able children. While few would
question the validity of this statement, there is little large-scale
evidence on the intergenerational transmission of IQ scores. Using a
larger and more comprehensive dataset than previous work, we are able
to estimate the intergenerational correlation in IQ scores, examining
not just average correlations but also how this relationship varies for
different subpopulations. We find that there is substantial
intergenerational transmission of IQ scores; an increase in father’s IQ
at age 18 of 10% is associated with a 3.2% increase in son’s IQ at the
same age. This relationship holds true no matter how we break the data.
This effect is much larger than our estimated elasticity of
intergenerational transmission of income of approximately .2.

Here are ungated versions, or here.  Note that a) this is based on Norwegian data, b) income elasticity declines with birth order, c) intergenerational IQ elasticities are broadly the same across different levels of education for the father, d) the sample size is much larger than usual, and e) the author caution against assuming this is entirely a genetic effect; in another study large family size lowers IQ for instance, adjusting for parental IQ.

It has been found, for example, that women can predict a man’s
interest in infant children from his face. Trustworthiness also shows
up, as does social dominance. The latest example comes from a paper
just published in the Proceedings of the Royal Society by
Justin Carré and Cheryl McCormick, of Brock University in Ontario,
Canada.

The thesis developed by Mr Carré and Dr McCormick is that
aggressiveness is predictable from the ratio between the width of a
person’s face and its height. Their reason for suspecting this is that
this ratio differs systematically between men and women (men have wider
faces) and that the difference arises during puberty, when sex hormones
are reshaping people’s bodies. The cause seems to be exposure to
testosterone, which is also known to make people aggressive. It seems
reasonable, therefore, to predict a correlation between aggression and
face shape.

The bottom line is that a wide face predicts male aggression.  The study is based on photos of hockey players and measures of their combativeness.  Here is the full story.  Here is an Oprah magazine article on how women can camouflage a wide face with the right haircut.

Even fathers with only one wife provided no [longevity] benefit to their grandchildren, a finding supported by previous research.

That is based on a study of Finnish church data from the 18th and 19th centuries.  The thrust of the entire piece is the claim that polygamous men will live longer than monogamous men.  But note, all you Lotharios out there, this result is correlated with actual [multiple] marriage, not running around in bars and the like.

Getting stuck on their backs and dying of suffocation
Attacked by flies
Eaten by maggots
Being attacked by dogs or any other living creature
Being frightened into a heart attack by imagining the dog is going to attack, even though it is not
Drowning (Are we surprised sheep cannot swim?)
Suffocating in snow (surprisingly common)
Hoof infections that poison the blood
Almost exploding with grass because they have eaten too much and are unable to pass wind
If they get too hot
If they get too cold

That’s from Marti Leimbach and I wonder how many sheep die of old age.  With that, it is time to leave Santiago and return home.

…given self-indication we should expect to be in a
finite-probability universe with nearly the max possible number of
observer-moment slots.  Such universes seem large enough to have at
least one inflation origin, which then implies at least one (and
perhaps infinitely many) large regions of time-asymmetry like what we
see around us.  And if, as it seems, most observer-moments in such universes are in
such regions, then we have explained why we see what we see.

That’s from Robin Hanson, one of the least evil people I have met.  I do not have the background to judge this claim but it makes sense to me.  The question is whether you are willing to bite the bullet when you realize the other implications of what Robin is postulating, namely that you start dealing with expected values of infinity, most of all in ethics…

By the way, via Andrew Sullivan, here is new evidence for dark energy.

That’s what some environmentalists said they feared when Planktos, a
California-based concern, announced it would embark on a private effort
to fertilize part of the South Atlantic with iron, in hopes of
producing carbon-absorbing plankton blooms that the company could
market as carbon offsets. Countries bound by the London Convention, an
international treaty governing dumping at sea, issued a “statement of
concern” about the work and a United Nations
group called for a moratorium, but it is not clear what would have
happened had Planktos not abandoned the effort for lack of money.

Here is the whole story.

Maybe not, maybe you just think they are:

Leading papers in a journal’s issue attract, on average, more citations than those that follow.  It is, however, difficult to assess whether they are of better quality (as is often suggested), or whether this happens just because they appear first in an issue. We make use of a natural experiment that was carried out by a journal in which papers are randomly ordered in some issues, while this order is not random in others. We show that leading papers in randomly ordered issues also attract more citations, which casts some doubt on whether, in general, leading papers are of higher quality.

Here is the full paper, courtesy of Pluralist Economics Review.

Remember all those studies showing that people claim they are above-average drivers?  Or above-average at other things they do?  It may not just be self-deception.  Here is the latest:

…we find it easier to consider the favourable evidence for a single
person than we do for a whole group. Consistent with this is the
finding that people tend to be biased when comparing any single
individual, not just themselves, against a group of others.

There’s
also the possibility that we’re biased towards the "target" in any
comparison. The "target" is the entity that is being measured up
against some benchmark. Following this logic, if I asked you how good
all other drivers are compared with you (thus making other drivers the
"target" of the comparison and you the benchmark), then this ought to
reduce the bias you’d show towards yourself.

…A new study has tried to get to the bottom of what causes the "above
average effect" by pitching these three explanations against each
other. Zlatan Krizan
and Jerry Suls Dozens asked dozens of undergraduates to list a group of
friends or acquaintances, to take one member of that group and then
compare that individual with the rest of the group on some attribute –
say, generosity.

Of the three factors, our difficulty in seeing the quality of a group, relative to the quality of an individual, seems to be the primary source of bias in the ranking. 

Fortunately, I am better at avoiding that bias than are my readers.

Yes, men are also, to their own detriment, continually surrounded with images of exceptionally attractive women. But this has less practical import, because–to say it once more–women choose.

Or:

The decline of matrimony is often attributed to men now being able to “get what they want” from women without marrying them. But what if a woman is able to get everything she wants from a man without marriage? Might she not also be less inclined to “commit” under such circumstances?

This essay is not politically correct and at times it is misogynous and yes I believe the author is evil (seriously).  The main behavioral assumption is that women are fickle.  So they are monogamous at points of time but not over time; Devlin then solves for the resulting equilibrium, so to speak.  The birth rate falls, for one thing.  The piece also claims that the modern "abolition" of marriage strengthens the attractive at the expense of the unattractive.  Some of you will hate the piece.  I disagree with the central conclusion, and also the motivation, but it does seem to count as a new idea.  If you’re tempted, read it.

I thank Robin Hanson for the pointer.

For the past week or so the newspapers have been trumpeting a new study showing no difference in average math ability between males and females.  Few people who have looked at the data thought that there were big differences in average ability but many media reports also said that the study showed no differences in high ability.

The LA Times, for example, wrote:

The study also undermined the assumption — infamously espoused by former Harvard University President Lawrence H. Summers in 2005 — that boys are more likely than girls to be math geniuses.

Scientific American said:

So the team checked out the most gifted children. Again, no difference. From any angle, girls measured up to boys. Still, there’s a lack of women in the highest levels of professional math, engineering and physics. Some have said that’s because of an innate difference in math ability. But the new research shows that that explanation just doesn’t add up.

The Chronicle of Higher Education said:

The research team also studied if there were gender discrepancies at the highest levels of mathematical ability and how well boys and girls resolved complex problems. Again they found no significant differences.

All of these reports and many more like them are false.  In fact, consistent with many earlier studies (JSTOR), what this study found was that the ratio of male to female variance in ability was positive and significant, in other words we can expect that there will be more math geniuses and more dullards, among males than among females.  I quote from the study (VR is variance ratio):

Greater male variance is indicated by VR > 1.0. All VRs, by state and grade, are >1.0 [range 1.11 to 1.21].

Notice that the greater male variance is observable in the earliest data, grade 2.  (In addition, higher male VRS have been noted for over a century).  Now the study authors clearly wanted to downplay this finding so they wrote things like “our analyses show greater male variability, although the discrepancy in variances is not large.”  Which is true in some sense but the point is that small differences in variance can make for big differences in outcome at the top.  The authors acknowledge this with the following:

If a particular specialty required mathematical skills at the 99th percentile, and the gender ratio is 2.0, we would expect 67% men in the occupation and 33% women. Yet today, for example, Ph.D. programs in engineering average only about 15% women.

So even by the authors’ calculations you would expect twice as many men as women in engineering PhD programs due to math-ability differences alone (compare with the media reports above).  But what the author’s don’t tell you is that the gender ratio will get larger the higher the percentile.  Larry Summers in his infamous talk, was explicit about this point:

…if one is talking about physicists at a top twenty-five research university, one is not talking about people who are two standard deviations above the mean…But it’s talking about people who are three and a half, four standard deviations above the mean in the one in 5,000, one in 10,000 class. Even small differences in the standard deviation will translate into very large differences in the available pool substantially out.

If you do the same type of calculation as the authors but now look at the expected gender ratio at 4 standard deviations from the mean you find a ratio of more than 3:1, i.e. just over 75 men for every 25 women should be expected at say a top-25 math or physics department on the basis of math ability alone (see the extension for details on my calculation).  Now does this explain everything that is going on?  I doubt it.  As Summers also pointed out it takes more than ability to become a professor at Harvard and if there are variance differences in characteristics other than ability (and there are) we can easily get a even larger expected gender ratio.

Does this mean that discrimination is not a problem?  Certainly not but we need the media and academia to accurately present the data on ability if we are to understand how large a role other issues may play.

Addendum 1: Andrew Gelman points out that perhaps alone among the media, Keith Winstein at the WSJ reported the story correctly.

Addendum 2: The authors show variance ratios of 1.11 to 1.21, I take a VR of 1.16.  If we set the female variance to 1 this implies the standard deviation for female ability is 1 and for male ability 1.077.  Using an online calculator for the Normal distribution you can find that given their standard deviation .0102% of males have ability of 4 or greater (4 female sds) but given their sd only .0032% of females can be expected to have the same level of ability, thus a gender ratio of 3.18.

Note that we are assuming that mathematical ability is normally distributed – we know the data fit this distribution around the mean but we don’t know much about what happens at the very top.

I had never thought of this:

In a sense, base 3 is the best of the integer bases because 3 is the integer closest to e…Suppose you are creating one of those dreaded telephone menu systems — press 1 to be inconvenienced, press 2 to be condescended to, and so forth.  If there are many choices, what is the best way to organize them?  Should you build a deep hierarchy with lots of little menus that each offer just a few options?  Or is it better to flatten teh structure into a few long menus?  In this situation a reasonable goal is to minimize the number of options that the wretched caller must listen to before finally reaching his or her destination.  The problem is analogous to that of representing an integer in positional notation: the number of items per menu corresponds to the radix r, and the number of menus is analogous to the width w.  The average number of choices to be endured is minimized when there are three items per menu.

I have no idea if it is correct.  It is from the often quite interesting Group Theory in the Bedroom, and Other Mathematical Diversions, by Brian Hayes.