Archive for May, 2010

May 17 2010

Sperm Sorting

I was recently asked about the legitimacy of sperm sorting as a way to choose the gender of your child. This is a topic I had been researching for another project anyway, so I thought I would report my findings. This is a good topic for skeptics because it may seem dubious at first glance, but in fact there is serious science behind sperm sorting. But there is also some pseudoscience mixed in.

Genetic gender is entirely determined by the sperm from the male. Women have two X chromosomes and so can only contribute an X. Men have one X and one Y, and so can contribute one or the other, which determines the sex chromosomes of the child. (I wrote “genetic gender” because there are non-genetic hormonal factors in the womb and hormonal abnormalities that can influence sexual development.) Therefore roughly half of the sperm rushing to be the victor in the conception race carry one X chromosome and will result in a girl, while the other half carry one Y chromosome and will result in a boy.

If we could separate out the Ys from the Xs, then we could control the resulting gender of the child. The X chromosome is larger than the Y. Since each sperm is essentially just a tight packet of genetic material connected to a tail, the weight of each sperm is largely determined by the weight of each chromosome.

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14 responses so far

May 14 2010

Logic and Creationism

I spent my allotted blogging time this morning debating over e-mail with a creationist who professes to be interested in logic. So, for your edification, here is the latest exchange in a point-counter point style.


Me: It is not just my opinion – it is the opinion of the vast majority of the scientific community. The inescapable conclusion is that you are smarter or better informed than 99% of working scientists – it doesn’t mean you are wrong, but that should give you pause.

Duane: You’re correct in the fact that the majority of the scientific community accepts what you believe as well. But there are explanations for that phenomenon. Besides, I have lived too long and know too much for that to give me pause. We have enough examples in old and new history of the majority being WRONG. I can’t just blindly accept something just because the majority believes it. Galileo comes to mind; how about climate change. We could go back to a whole host of scientific pronouncements about food and health and see it has changed from one side of the spectrum to the other over the years.

Me: There is no example of the scientific community in modern times being completely wrong about a 150 year consensus such as evolution. That would be completely unprecedented. Galileo is not a good analogy – he was not bucking a scientific consensus but religious dogma. Climate change is not a good analogy – the consensus is far more recent, not nearly as solid as evolution, and you cannot assume that it has been rejected or disproved – at the very least this is still controversial. Similar with food and health – I am a physician and very familiar this history and evidence. There is nothing here even remotely similar to evolution.

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102 responses so far

May 13 2010

IOM Report on Supplement Regulation

The Institute of Medicine (IOM) is an organization of independent scientists and experts who are tasked with providing, “independent, objective, evidence-based advice to policymakers, health professionals, the private sector, and the public.” In my experience they generally do good work – those IOM reports I have read in areas that I have some knowledge seem to be thorough and objective.

They were recently tasked by the Food and Drug Administration (FDA) to prepare a report on the science behind health claims for food and drugs. Their report is now in, and the results are in accord with my own writings on the topic. They conclude, basically, that there should be a rigorous standard of evidence for not only drugs but also health claims made for food and supplements as well.

Their key points focus on the fact that many food and supplement claims are based upon basic science research – the use of biomarkers instead of clinical outcomes. They point out that extrapolation from biomarkers to health outcomes is problematic, and they outline methods the FDA can use to standardize the use of biomarkers. This is a valid point, but I am not sure why they focused as much as they did on this one point.

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18 responses so far

May 12 2010

I Don’t Feel Your Pain

A recent study uses EEG to look at brain activity in doctors and control subjects while viewing another person being poked with either a needle or a cotton swab. The control subjects showed activity in parts of the brain consistent with empathy – a negative experience in reaction to the pain of  the other. The doctors, however, did not demonstrate this brain activity.

These results, while preliminary, are not surprising to me at all. You may find it odd that a doctor, who is supposed to be especially attentive to the comfort of their patients, would be inured to their pain. But this makes perfect sense.

Let me start by recounting my own personal experience as a representative anecdote. The first invasive procedure most medical students learn is blood drawing, which involves sticking a needle into the vein of a patient in order to fill tubes with blood to send off to the lab.

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20 responses so far

May 11 2010

Dialogue with a 9/11 Truther

Published by under Conspiracy Theories

Eric Carlson, a listener of the SGU, is also a self-described 9/11 truther. He has written an extensive, if belated, reply to our discussion of claims made by 9/11 conspiracy theorists back in September of 2005. For a change of pace I thought I would answer some of his points.

I will start by noting that Eric is quite respectful throughout and does what few people, in my experience, do – he admits legitimate points on the other side, rather than finding some way to dismiss every single point we make, valid or not.  For brevity I will not review the points on which he agrees with us. You can read them for yourself on his blog post. I will simply summarize/quote his points of contention and respond.

His first point has to do with melting steel. We pointed out that, while the temperatures of the fires at the WTC towers were not hot enough to melt steel, they were hot enough to weaken the steel sufficiently to cause the collapse. Eric admits this point, but then counters:

While the Skeptic present a strong argument based on the limited facts they present, they fail to note the existence of Molten Steel in the wreckage.  While the Skeptics may call this point anomaly hunting, the educated Conspiracy Theorists will demand that physical evidence be included in the analysis.

This is an assumed premise followed by a straw man. Eric does something I find extremely common among conspiracy theorists – prematurely assuming facts that have not been established. As they say in court (at least on TV), “Objection, assumes facts not in evidence.”

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30 responses so far

May 10 2010


Language is a powerful but tricky thing – it not only is a tool for expressing our thoughts, to a large degree it shapes and frames our thoughts. This is true in every area of intellectual enterprise – where expanding one’s vocabulary literally expands the palette of ideas and concepts available, and technical or specialized language typically develops to precisely capture the necessary concepts.

This is true in my own field of medicine. I often caution students, for example, to use the proper terminology – not out of convention, but because sloppy language leads to (equals, in fact) sloppy thinking. The legs are not “below” the arms, they are “caudal” to the arms – further along the neuraxis away from the brain. Not only is it important to use terms that are precise, it is important (and a more subtle problem) to use words that are not prematurely precise. Disease taxonomy is often hierarchical, and if you commit yourself too early to a narrow branch, you will prematurely narrow your thinking as well. The patient did not present with “seizures”, they presented with “episodes” – and it is for us to determine if these episodes are seizures or something else.

Politicians and marketers use language differently from scientists and philosophers. The latter is concerned with precision and accuracy, while the former with emotion, deliberate vagueness, and false implication.

The specific example I am getting to today is a particular peeve of mine – the gross overuse of the term “therapy.” It seems you can throw the term “therapy” at the end of any activity and thereby imply that it has a specific medical application, or some benefit beyond the obvious pleasure or benefits of engaging in that activity. So now we have aromatherapy, massage therapy, music therapy, and dance therapy. “Therapy” has become a marketing term, like “natural” – rendered devoid of precise meaning and used to create vague implications.

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19 responses so far

May 06 2010

Waxman Fights for Sense in Supplements

I am sitting in an airport right now – traveling makes it very challenging to keep up with my multi-media output. Just getting the SGU out this week will be a challenge (but fear not – it will get out on time). So – I only have time for a short post this morning.

Recently Congressman Henry Waxman introduced a bill that would hold vitamin sellers accountable for the health claims that they make. This would be a sensible change to the current regulations in the US, which essentially amount to a free-for-all with a thin veneer of accountability. Right now there is almost no pre-marketing requirements for the supplement industry.

Thanks to DSHEA, companies (which increasingly include pharmaceutical companies – so forget your homey image of a  mom-and-pop vitamin store) are free to sell vitamins and “supplements” (which can include herbs used as drugs) without any requirement to provide evidence of safety and efficacy. They are even allowed to make pseudo health claims – so-called “structure and function” claims.

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8 responses so far

May 04 2010

Hypnotized by Charisma

Published by under Neuroscience

Have you ever found yourself saying, “What were they thinking?” or more importantly, “What was I thinking?” In the light of day (when your thinking at least appears to be more clear and rational) you may have a hard time understanding how you were fooled by a con man, caved in to a slick salesperson, or were taken in by a charismatic politician. It’s almost as if your brain were functioning differently.

Well – increasingly evidence suggests that perhaps it was. A recent study, looking at fMRI scans of Christians and non-Christians in response to the speech of a faith healer, is just the latest in a series of studies which sheds an interesting light on how our monkey brains work.

But first, some background.

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20 responses so far

May 03 2010

More Anti-Science at the Huff Po

One of the challenges of trying to be scientific, and an honest intellectual, is that judgment is often required in assessing a claim or topic. The problem with relying upon one’s judgment is that it is fraught, even overwhelmed, with personal bias. The “default mode” of human behavior (which means most people do this most of the time) is to construct an elaborate rationalization for what we already believe, and want to believe. The more intelligent we are, the more sophisticated and elaborate our rationalizations – giving more confidence in our conclusions, but not necessarily deserved.

The solution to this problem is to develop a specific intellectual skill set – knowledge of the many and various ways in which we bias our thinking and the constant application of this knowledge to our own beliefs. In other words, we need to be skeptical, especially of ourselves. But not just skeptical in attitude, systematically skeptical of the process of our own thought. But since this is necessarily self-referential (we can bias our assessment of our biases) it is also necessary to check your beliefs and thinking against other people, people with different perspectives – from different backgrounds, areas of expertise, and cultures.

The opposite of this approach is to be insular, to have a self-contained belief system that feeds on itself but which is completely disconnected from logic and reality. Humans seem to have an unfortunate penchant for falling into such self-contained belief systems, cults being the ultimate expression of this tendency. Conspiracy theories are another manifestation.

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