Scientific American on energy & cosmology

Tamara Davis’s cover article (paywall) in the latest issue of Scientific American is about the old puzzle of whether it makes sense to talk about energy conservation in the expanding Universe.  It has the good taste to refer to my work with David Hogg on the nature of the redshift, which is at the heart of this question.   In fact, one of the figures in the article is essentially a slick, nice-looking version of something from our paper:


I think the article’s very good.  I think it gets the science right and emphasizes pretty much the right things.

More on the Larry Summers hypothesis

I want to make a few followup points regarding yesterday’s post about the gender gap in the sciences.

Just to recap, the “Larry Summers hypothesis” is the idea that differences in intrinsic intellectual ability can explain the underrepresentation of women in academic science.  More specifically,  the proposed explanation is that, even if there’s no difference in average ability, men tend to have intellectual ability (as measured by scores on various tests) that scatters more widely than women.  That means that men populate the very extreme highs and lows of the distribution much more than women.  If being a successful scientist requires being in the extreme high end of this distribution, then that might explain the gender gap.

I don’t think this is likely to be a significant part of the explanation, for reasons I tried to explain.  The biggest one is that I don’t think that success in a scientific career is sufficiently strongly correlated with intelligence (where the “intelligence” is defined to mean “the thing that the tests in question measure”).  To be more specific, I certainly don’t think that it’s strongly correlated with presence in the high-end tail of the intelligence distribution, which is where the gender differences supposedly lie.

If we were just trying to explain the preponderance of men among Nobel Prize winners, maybe a case could be made for this effect (although even then I’m not sure).  But in fact the gender gap shows up much earlier and grows at each step.  (The “leaky pipe” is the usual metaphor here.)  More men than women major in physics; the ratio skews further at the Ph.D. level, still further at the level of faculty jobs, and even further among tenured faculty.  If you think that all of this is because of effects in the top 1% tail of the intelligence distribution, I’m afraid you’re making  a flattering overestimate of the physics community’s intelligence.  We’re tolerably bright, but not that bright.

But there are a couple of things I want to make clear:

1. People sometimes use your attitude about the Summers hypothesis as a proxy for your attitude about all sorts of other things: if you disbelieve the Summers hypothesis, you must believe in the mind as a blank slate, with no room for intrinsic biological differences between the sexes.  Conversely, if you believe in the Summers hypothesis, (according to some) you must be a sexist.  Those attitudes are ridiculous.  In particular, although I think the Summers hypothesis is probably wrong, I think that that intrinsic cognitive differences in the sexes are quite likely to be real and may explain all sorts of other phenomena. I’m even generally sympathetic to the evolutionary psychology point of view, which is anathema to a lot of people who argue against the Summers hypothesis.

(Incidentally, if I may play armchair psychologist for a moment, it seems to me that the authors of that NOVA blog post, which got me started on this whole subject, are making this error: they saw Tierney as sympathetic to the Summers point of view and concluded that he must believe in the whole constellation of despised ideas that they associate with that point of view.  I can’t see any other reason they would have so egregiously misrepresented what he said.)

2. I don’t think that adherents of the Summers hypothesis are bad people, and I don’t think that the hypothesis should be ruled out of the bounds of polite discussion (as many people seem to).  It’s an a priori possible explanation of the observed data, which is either true or false.  It has the right to a hearing, and its probability of being correct can and should be judged on empirical grounds, like any other hypothesis.  Personally, I think it must be found wanting on those grounds.  But it should not be ruled out a priori because we don’t like its social or political implications.

3. It may seem to follow from point 2 that Larry Summers got a raw deal, but my sympathy for him is extremely limited.  If you’re a politician (and yes, a University president is a politician), then you should know better than to speak off the cuff about an extremely controversial topic about which you clearly have given very little thought.  He made a boneheaded move in raising the subject the way he did, and he got what was coming to him.  Moreover, as is often the case when politicians are brought down by gaffes, this one probably wouldn’t have brought him down if he didn’t have a history of alienating people.

Is John Tierney pulling a Larry Summers?

NY Times columnist John Tierney wrote a pair of columns on the much-discussed question of why women are underrepresented in math and the physical sciences.  I didn’t see these columns until someone pointed out this response to them on the PBS Inside NOVA blog:

Why aren’t there more women in the upper echelons of science? It’s a question with many answers, but John Tierney at the New York Times is only interested in one: Maybe women just aren’t smart enough.

This is such an inaccurate description of Tierney’s position that the authors would seem either not to have read his columns or to be deliberately misrepresenting them.  Tierney:

So why are women still such a minority in math-oriented sciences? The most balanced answer I've seen comes from two psychologists at Cornell, Stephen J. Ceci and Wendy M. Williams €” who, by the way, are married and have a daughter with a graduate degree in engineering. After reviewing hundreds of studies in their new book, "The Mathematics of Sex" (Oxford), they conclude that discrimination is no longer an important factor in keeping out women.

They find consistent evidence for biological differences in math aptitude, particularly in males' advantage in spatial ability and in their disproportionate presence at the extreme ends of the distribution curve on math tests (the topic of last week's column). But given all the progress made in math by girls, who now take more math and science classes than boys and get better grades, Dr. Ceci and Dr. Williams say that differences in aptitude are not the primary cause of the gender gap in academic science.

Instead, they point to different personal preferences and choices of men and women, including the much-analyzed difference in the reaction to parenthood. When researchers at Vanderbilt University tracked the aspirations and values of mathematically gifted people in their 20s and 30s, they found a gender gap that widened after children arrived, with fathers focusing more on personal careers and mothers focusing more on the community and the family.

Dr. Ceci and Dr. Williams urge universities to make it easier for a young scientist to start a family and still compete for tenure, but they don't expect such reforms to eliminate the gender gap in academic science. After all, the difficulty of balancing family and career is hardly unique to science, and academia already offers parents more flexible working arrangements than do other industries with smaller gender gaps.

The gap in science seems due mainly to another difference between the sexes: men are more interested in working with things, while women are more interested in working with people. There's ample evidence €” most recently in an analysis of surveys of more than 500,000 people €” that boys and men, on average, are more interested in inanimate objects and "inorganic" subjects like math and physics and engineering, while girls and women are more drawn to life sciences, social sciences and other "organic" careers that involve people and seem to have direct social usefulness.

Ceci and Williams (and hence Tierney) may be right or they may be wrong.  But to take this position and replace it with “women just aren’t smart enough” is shamefully dishonest.

For what it’s worth, my best guess is that the key factors explaining the gender gap are:

  1. Girls being discouraged from doing math and science in school, starting from a very young age, by teachers, parents, and peers.
  2. The family-unfriendly nature of the tenure-track job process.
  3. Discrimination (almost 100% unconscious but no less harmful as a result) against women scientists by their peers.

Tierney does give more credence than I do to the Larry Summers hypothesis, that the gender gap is partly explained by the fact that more men than women lie at the extreme high-end tail in the distribution of math ability (as well as the other tail).  The NOVA blog post does a good job at laying out some of the reasons why this seems like an unlikely explanation.  Among many other reasons:

  1. If this were the explanation, the effect would be uniform across cultures, but it isn’t.
  2. In my experience, lying in the extreme tail in the distribution of scores on math tests is not all that highly correlated with being a successful scientist.  On the contrary, many of those extreme outliers lack the other skills needed for success in science.

So to the extent that Tierney is advocating this as the explanation for the gender gap, I think he’s probably wrong.  But it’s not fair to replace his actual position with an inflammatory and inaccurate straw man.

Unweaving the rainbow

I like this Abstruse Goose comic about how scientists view the world:

Abstruse Goose 275

The author’s commentary on this is “Poor bastards.”  Presumably he’s being ironic, but lots of people do feel this way.  But I’m with Feynman:

I have a friend who’s an artist, and he sometimes takes a view which I don’t agree with. He’ll hold up a flower and say, “Look how beautiful it is,” and I’ll agree. But then he’ll say, “I, as an artist, can see how beautiful a flower is. But you, as a scientist, take it all apart and it becomes dull.” I think he’s kind of nutty …. There are all kinds of interesting questions that come from a knowledge of science, which only adds to the excitement and mystery and awe of a flower. It only adds. I don’t understand how it subtracts.

(From What Do You Care What Other People Think?)

Rewiring the brain

(Warning: I’m going way far away from any area where I could possibly claim expertise here.)

Nicholas Carr has a new book coming out, as well as an article in Wired,  about the possibility of cognitive changes arising from the huge changes in the way we consume information in the Internet age.  I think that’s an interesting subject, but the reviews and discussions of Carr’s writing have emphasized a trope that I think is very misleading and alarmist: the Internet, they say, is rewiring our brains.

It seems to me that the rewiring-our-brains language is intended to scare people, provoking a reaction similar to Miles Monroe‘s (“My brain?  But that’s my second favorite organ!”).  But it’s not clear that it really means anything.  Anything that changes your mental state (remembering something, forgetting something, learning a new skill, etc.) results in physical changes (“rewiring”) of your brain.

It’s interesting to ask whether the Internet is changing the ways we think, and if so, whether those changes are good or bad, and it’s certainly good for psychologists and neuroscientists to do experiments to try to figure out the mechanisms.  But let’s discuss the results dispassionately without scaremongering.

Steven Pinker said it well in his book The Blank Slate:

All this should be obvious, but nowadays any banality about learning can be dressed up in neurospeak and treated like a great revelation of science. “Talk therapy, a psychiatrist maintains, can alter the structure of the patient’s brain” [says a newspaper article].  I should hope so, or else the psychiatrist would be defrauding her clients … A special issue of the journal Educational Technology and Society was intended “to examine the position that learning takes place in the brain of the learner, and that pedagogies and technologies should be designed and evaluated on the basis of the effect they have on student brains.”  The guest editor (a biologist) did not say whether the alternative was that learning takes place in some other organ of the body like the pancreas or that it takes place in an immaterial soul.

And just recently,  there’s a nice blog post by Vaughan Bell explaining why you shouldn’t pay any attention when people tout a scientific result as having to do with neuroplasticity:

Neuroplasticity sounds very technical, but there is no accepted scientific definition for the term and, in its broad sense, it means nothing more than ‘something in the brain has changed’. As your brain is always changing the term is empty on its own.

He goes on to describe the wide range of things people can mean when they use this term.

Someone needs to teach Will Shortz about emf

As far as I can tell, quality control for the New York Times crossword puzzle is very good but errors do creep in.

This past Friday, the clue for 37 Across was “Symbol of electromotive force.”  The intended answer: epsilon.  I’ll admit that the symbol for emf looks kind of like an oversized epsilon, but it’s not one: it’s a capital E in a script font.  In over 20 years of doing and teaching physics, I’ve never seen emf denoted by an epsilon.

Oddly enough, the last error I noticed in a Times crossword also had to do with emf.  In that case, the error was more unambiguous.  The clue was “Energy expressed in volts”, which is actually meaningless: volts aren’t a unit of energy.