What “Climate Gate” tells us about scientists…

…that they are often less like the Professor and more like all of the other denizens of the island.

 

Religion and vaccination

Here we have a story from Grand Rapids, MI, about a woman who could lose her job at a hospital because she is refusing to be vaccinated against influenza. The hospital makes flu shots a condition of employment. Such a requirement makes sense on multiple levels. Hospitals are a great place to catch, and spread, viruses, so flu vaccinations are especially important for hospital workers. This benefits not only the workers themselves but also their patients and the public at large.

The woman’s refusal is on religious grounds:

“I was raised a Christian,” the Spectrum Helen DeVos Children’s Hospital employee said. “And it was my belief that I feel like God created us in his image. He created our body and created our immunity.”

Soooo…..does this mean that God, in whose image “our body and…our immunity” are made, is afflicted by the hordes of viruses and other infectious diseases that present such a challenge to us, and that he is dumb enough not to trust the power of reason to seek ways to compensate for those frailities? Well, maybe he only created our bodies and our immunity in his image, and left our intellects to be shaped by superstition and a deficient educational system.

 

Evolution, spite, and ideological suicide bombs

11 October 2009

Recently we’ve seen allegations by a politician and a pundit that conservative leaders are being “spiteful” by taking positions that undermine their political foes (especially President Obama), even though these positions would seem to make them look bad. For example conservatives celebrated Obama’s failure to land the Olympics for Chicago even though this made them seem somewhat unpatriotic. Rush Limbaugh’s expression of hope that Obama fails to deliver his domestic political agenda–whether or not things get better–is another example.

This behavior has been compared to that of “bratty teenagers.” Of course, teenagers have no monopoly on juvenile spitefulness. My favorite example is from a child of a much younger age. When my son was 3 or 4, his bedtime ritual included having one of his parents gently scratch his back. On those exceedingly rare occasions when he was mad at his parents, one way he retaliated was to yell, “I’m not going to let you scratch my back tonight!”

Spite in any form raises the profound scientific question: “what’s up with that?”

Actually, the question that is raised is a deep one about the evolution of behavioral decisions that mediate selfishness and cooperation.

People interested in social evolution recognizes four kinds of patterns depending upon the benefits and costs that accrue to the parties involved. (“Parties” being an especially relevant term in this case.)

• Selfishness: one party acts to benefit himself at the expense of another
• Mutualism: both parties experience a net benefit (i.e., outweighing any costs of the action)
• Altruism: one party acts in a way that benefits someone else, but at some net cost to himself
• Spite: one party acts in a way that harms another, but he harms himself in the process

We can see all of these on display in human societies, and it is certainly anthropomorphism that motivated the naming of these categories. The scientific value of this classification is to focus attention on the pressures that may favor the evolution of different kinds of behavioral interaction in social groups.

Some of these behavioral categories are easier to account for than others. Selfishness, for example, is often assumed to be the default condition of a Darwinian world “red in tooth and claw.” Mutualism too is easy to understand, and nature–red or not in tooth and claw–abounds with examples of animals (and plants) helping each other to the mutual benefit of all. Think of bees and the flowers they pollinate: bees get food and flowers get their gametes dispersed accurately to other flowers.

Altruism has been a more of knotty problem. It has invited extensive study because there are numerous examples of apparent altruism in the animal (and human world), and because acts of self-sacrifice for others would fly in the face of a Darwinian account of evolution. This paradox has largely been resolved by recognizing that most apparently selfless acts actually result in some selfish benefit to the actor either through kinship (nepotism), reciprocity (you-scratch-my-back-and-I’ll-pay-good-money-for-it), or hidden mutualistic benefits.

This brings us to spite, which is an even harder problem than altruism because it is harder to find clear-cut cases in nature and because it is an even more challenging Darwinian paradox. How would any tendency to harm others evolve–or be allowed to persist in the face of natural selection–if it also entailed disadvantages to the harm-doer?

As mentioned, there are very few candidate examples of spite in nature, but there are some. One way to explain these is to identify hidden advantages to kin who might benefit as a consequence of a spiteful act that harms the actor. Another is to uncover “indirect reciprocity“–a spiteful act might hurt both the actor and the party that he harms (spiter and spitee?), but someone else who observes this act may benefit. If that individual (the enemy of my enemy) later turns around and helps the original actor, then the spiteful act may have been worth it. Thus, again, apparent self-sacrifice would have a self-serving consequence.

Do these explanations capture what does on in human societies, where spite is so remarkably common? Take an extreme instance of spite–suicide bombings. Here, the mildness of the term “spite” seems incommensurate to the horror of the act, but it raises the same evolutionary paradox in a particularly clear way. In the case of religiously inspired suicide bombers, the commonly understood motivation has to do with a delayed selfish benefit–eternal bliss. Science doesn’t allow recourse to supernatural payoffs, and in any case our stated motives may have nothing to do with Darwinian payoffs–the ways in which our actions affect the probability of our genes, or copies residing in kin, making it to the next generation. A Darwinian account of suicide bombings would predict that there is some selfish benefit, for example an enhancement of the well-being of the family of the bombers.

Let’s return to the somewhat milder spitefulness those who wade into political debates wearing ideological bomb vests–celebrating any failure of a political opponent even at the risk of blowing themselves up. It is not hard to imagine the selfish calculations (whether conscious or unconscious) that may underlie this stance. The key is that the failure of one’s enemy may pave the way for the future success of oneself or one’s own friends and family.

The troubling question is how the incentives wound up being set this way. It is not hard to imagine a different kind of society–because they do in fact exist–in which people can be guided by selfish motives but act in a way that benefits themselves as well as others. A society that embraces mutualism instead of spite. How have the payoffs been rigged so that spite is the attitude that prevails?

 

Learning curves

Today, yet again, I heard the phrase “steep learning curve.” This has always bothered me. Every time I hear this (quite overused) term, I find myself momentarily confused about what is meant. The reason for my confusion is that my notion of a steep learning curve–from studies of learning in animals and in human subjects–implies something different about the inherent difficulty of the task than what most users of the term seem to mean.

Most people who use the term “steep learning curve” are talking about something that is hard. To take just one example–one of the first I happened to encounter in a Nexis search of the term–this WaPo story is about an actress, Lauren Conrad, who is daunted by having to “learn a lot of facts and big words” for a guest-starring role on “The Family Guy.” The headline says she had a steep learning curve, and implied she found the task hard. To see whether this usage is typical, I spot-checked the Nexis results going back a few years. Every single article I opened equated steep learning curves with hard tasks.

By contrast, I tend to think of a steep learning curve as something that occurs when the task is easy. This is because a learning curve typically charts an animal’s (or human’s) response as a function of time or experience. More specifically, the learning curve shows the number or percentage of correct responses as a function of the number of attempts. Or it might show the error rate as a function of experience, in which case the learning curve would slope downward. Either way, the steeper the curve, the quicker the learner improves its performance. For example, here are graphs from a study on sequential learning by rats in which animals having to learn to press individual bars presented in a circular array in a particular sequential order.

Some versions of the task are easier for rats than others, and result in steeper learning curves.

I’ve often wondered how the jargon got co-opted. For a while my favorite hypothesis assumed three stages to the co-opting of the term. Stage 1: people were thinking something like “Wow, Lauren Conrad had a tough hill to climb in learning all those facts and big words for ‘The Family Guy’.” Stage 2: Learning curves are kind of like hills. Stage 3: Steeper hills are harder to climb (or descend safely?), and so, therefore, are steeper learning curves.

Studying instances of the term “steep learning curve” in my Lexis search, I realized another dimension of the usage: when people talk about someone having to climb a steep learning curve, they almost always mean that the task is not only hard, but it has to be done quickly.

So, there is something going on about motivation and not just the inherent difficulty of the task.

Here’s an example of different (ascending) learning curves measured when the inherent difficulty is presumably identical (a rat has to learn which bar needs to be pressed to get the reward), but the motivations are different.

Rats learn quicker when more motivated

The motivator in this case is a drug that is delivered when the correct bar is pressed. The higher the dose of the drug, the steeper the learning curve. See the original source of this figure in Addiction Science.

So I think I have a new insight about the co-opting of the term “steep learning curve.” When someone needed to talk about how many facts and big words Lauren Conrad had to learn, what was of interest was not really how inherently difficult the task was to achieve, but how urgently Lauren needed to achieve it. This kind of usage, then, is obviously connected with the motivations of the person doing the learning, whether it is money, fame, or drugs.

Understanding the usage in this way doesn’t dispel my discomfort when I hear the term. The problem is that the relationships among learning and motivation and performance are really complicated. A quick improvement in performance could be a result of the task being easy or the learning being very motivated. Saying the learning curve is steep doesn’t indicate which is which. But I have no intention of trying to change this incredibly common usage pattern. This would be like trying to get people to pronounce “forte” or “finance” or “dissection” the way I was taught. Some hills are too steep to climb.

As for the phrase “going forward”……

____________________

Update: Wikipedia has a decent review of the science and language of learning curves: http://en.wikipedia.org/wiki/Learning_curve

Update 10/6:  corrected some typos

 

What is behavior?

I was going to entitle this entry “What is an Ethologist?” I decided, however, that this begs a question that is a bit more interesting, hence the title I selected.

The conventional definition of “ethology” is “the scientific study of animal behavior.” The field took shape in the early part of the 20th century, growing out of the sciences of zoology and physiology. From zoology came the goals and methods of comparative biology for understanding the diversification and modification of traits as species evolve. From physiology came the quest to understand the biological machinery underlying complex organismal traits. Scientists trained in these older traditions realized that methods developed for the study of bones, muscle twitches and glandular secretions could be applied to the more ephemeral and variable domain of behavior. In recognition of the importance of this new field, the 1973 Nobel Prize for Physiology or Medicine was awarded to three pioneering ethologists–Konrad Lorenz, Niko Tinbergen, and Karl von Frisch.

Now we come to the question-begging part. If ethology is the study of behavior, what is that thing–behavior–that is the focus of study? It turns out to be a hard question to answer. Actually, it is an easy question to answer, but a hard one on which to find agreement among the answers different people provide. That’s the point of an article published in July 2009 in one of the leading journals in the field, Animal Behaviour. The article’s title: Behavioural biologists do not agree on what constitutes behaviour.

Before reading further, I encourage you to do what I did when I read that title–I decided on my own definition. That didn’t take long. I have thought about the topic for a long time, having taught the subject for many years, and having once been an editor of Animal Behaviour. So, I already had an opinion: behavior (back to American spelling) is what animals do as opposed to how they are built (morphology) or how their internal systems work (physiology). To extend this a little, behavior constitutes actions (including lack of movement) that may have consequences for the animal’s biological fitness, and that are mediated by internal systems for sensing the environment and controlling the body.

Before reading the article, I anticipated some of the objections that might be raised to my own definition. What about behaviors seen in non-animals such as plants (e.g. such as vines that climb) or microbes (such as bacteria that swim up and down chemical gradients)? What about physiological or morphological changes that are mediated by internal control system and that clearly have a behavioral role, but that don’t fit the notion of the animal “doing” something (e.g., changes in the color of the beak and plumage of male starlings when the breeding season arrives)? I knew my definition was a little ambiguous, but it still captures a big chunk of what ethologists study.

Such ambiguity is precisely the point of the Animal Behaviour article, which used two kinds of surveys to expose the fuzzy boundaries of people’s definitions of behavior. The first survey asked people to agree or disagree with a series of statements offering definitions of behavior. The second survey asked people to classify several phenomena as “behavior” or “not behavior.” The participants were practicing scientists whose work had something to do with behavior (including members of the Society for Plant Neurobiology–who knew?).

The results showed first that there was a lot of disagreement among people about how behavior should be defined, and what kinds of phenomena qualify as behavior. Even more striking was that people often disagreed with themselves: for example, they recognized things as behavior that were at odds with the definition they favored.

Perhaps this outcome isn’t so surprising. After all, behavioral phenomena are hard to pin down even when everyone would agree upon their classification as behavior and not something else. Consider the fox squirrel that I am watching out my window right now. It is moving over the lawn, alternating periods of travel with pauses, digging occasionally, burying occasionally, looking up occasionally. These behaviors vary in their expression each time they are done, and you can be sure that they vary among individuals. They unfold in an ongoing, highly variable sequence, making it hard to segment into elemental parts that can be measured, isolated, and reduced to underlying physiological explanations.

These  challenges inherent in studying behavior don’t undermine the legitimacy of ethology as a rigorous science.  They do, however, make the achievements of the early ethologists (including Darwin, who was the first ethologist of them all) all the more astonishing.

 

Try feeding a family

More evidence they think we’re stupid.

In reaction to the possibility that a tax might be imposed on “juice drinks and soda,” an outfit called Americans Against Food Taxes has come out with an ad that shows a fit, attractive mom hauling bags of 32-oz soda bottles out of her hatchback.

The key tag line:  “They say it’s only pennies.  Well those pennies add up when you’re trying to feed a family.”

Wow.

To see an intelligent analysis of the public health implications of a tax on sweetened beverages, see the recent report in the New England Journal of Medicine.

 

More on vestiges

In the previous post, I pointed to a site that lists the “Top 10″ vestigial organs. Number of 9 on this list has long been my personal favorite: the vestigial pelvic bones of modern whales. The reason it is my favorite is because of the role that it played in my own intellectual development.

From an early age, I have been fascinated by nature, and by animals in particular. When I was growing up, my family moved around a lot, but we always lived on the suburban fringe of one midwestern city or another, with easy access to woods, fields, and streams. My parents being tolerant of unsupervised wandering to a degree that was common then, but uncommon today, I would spend a lot of my free time exploring the tiny slices of nature available to me. When I was five, we lived in Fort Wayne across the road from a one-acre woodlot which seemed as vast and as bountiful as the great deciduous forests of eastern North America must have seemed to European settlers. At seven, in Finneytown (outside Cincinnati), I would bring home jars overfilled with tadpoles, unwittingly doing cruel experiments on the carrying capacity of pondwater microcosms. At 9, in Kenwood (a different Cincinnati suburb), there was a stream that my friends and I would follow to “Devil’s Dungeon” (a huge storm drain). Splashing through the stream we would find crayfish, frogs, turtles, and even a medicinal leech on one occasion.

There wasn’t much to these discoveries beyond the general show of admiration that young kids offer to things they are seeing for the first time, but they did feed my growing appreciation of the wonders of nature. And not just the extant wonders of nature. When on family picnics to various parks around the Cincinnati area, we would find stream beds that abounded in fossil creatures, most of which, I now realize, were bryozoans that must have lived about 440 million years ago (see this reference). I can still recall the sense of wonder I felt as I fondled these pieces of matter that once had lived and now were rock.

Then there was Mr. Terwilliger, my fifth grade science teacher. I LOVED science class–electroplating pennies with nickel, looking at dead insects through a microscope, but especially watching live animals in Mr. T’s classroom. He had a menagerie of snakes, snapping turtles, deer mice, white mice (who were there mainly to be food for the snakes), and crayfish (for the snapping turtles). It was around this time that I asked my mother, who had been a botany major in college, “If botany is the study of plants, then what is the study of animals?” When she told me “Zoology,” that’s when I decided to become a zoologist. That was before I decided I wanted to be an NFL football player, preferably a member of the Green Bay Packers under Vince Lombardi, a dream that had to be relinquished when I turned out not to grow up to six foot four and 250 pounds as I had planned. Fortunately zoology worked out as a decent backup plan.

I read a lot as a child, and I was particularly drawn to books about nature and science. I learned about vestigial whale bones in one of these books, again when I was around 10. I think it was by Roy Chapman Andrews, the great paleontologist and longtime director of the American Museum of Natural History, who wrote for children as well as for a professional audience and the general public. What I remember of the story is its essential logic.

• Whales are mammals through and through, though they look more like fish than they do like other mammals.
• Mammals originated on land, so the ancestors of whales must have been terrestrial and not aquatic creatures, and must have had four legs like other mammals.
• Whales have a lot of features that terrestrial mammals do, including hair, lungs, and forelimbs (their flippers) with five digits.
• Perhaps they also have traces of hind limbs even though none are visible on the surface.

The book then described how some scientist (the author? someone else?) arranged to dissect a whale that had washed up on a beach. Rooting through the blubber, he finds them, in just the spot where one would expect: bones equivalent to those in the pelvic girdle in mammals that walk on land. They were in the right location, they had the right shape, but they were now rudiments of the legs that they had descended from, with no function related to walking.

This absolutely floored me. I recall being completely amazed not so much by the facts that were revealed about nature, but by the power of human reasoning that was on display: that you can ask a question about the distant past (whether the ancestors of whales had hind legs), and then figure out a way to answer it.

It still amazes me.

 

Vermiform musings

Well, maybe the human appendix has a function after all. Long one of the textbook examples of a “vestigial organ,” a recent publication now reinterprets the appendix as serving a critical role in helping deal with contamination of food. Here is a Science Buzz article summarizing the research. Both detailed (i.e., microscopic) studies of the appendix and comparisons of the equivalent organ in other mammals provide evidence that this structure serves as a refuge where a reserve force of “good” bacteria can be maintained in the event of an influx into the intestines of toxic food-borne bacteria. The paper also suggests that appendicitis can be intepreted as a pathological response to a modern diet–a diet which the appendix was not evolved to handle.

Drawing of human small and large intestines, with appendix at lower left (4)

From http://www.gutenberg.org/files/18467/18467-h/images/advise028.png

So what? Well, the thing is that the “vermiform appendage” (as Darwin called it) has long played a role in arguments about the history of life, and especially the history of the human lineage. The interpretation of the appendix as a vestigial structure figured in first chapter of Darwin’s The Descent of Man. The chapter was entitled “The evidence of the descent of man from some lower form” (no beating around the bush there). In the popular imagination, this interpretation has hardened into dogma for all practical purposes, and continues to play a part in the “argumentarium” of defenders of an evolutionary world view. Vestigial structures are especially favored by critics of so-called “Intelligent Design creationism. The writers here and here make the standard argument: what kind of intelligence is it that produces a structure that is useless at best, and can even malfunction with lethal consequences on occasion? Gotcha!

So what if the appendix actually does have a function, and what if it actually is rather well configured for that function? Does this give solace to creationists? I’m sure it will, but it shouldn’t. Nature is replete with biological structures whose function was initially unknown or misunderstood before deeper studies reveal their contribution to the organisms survival. For example, a few pages after his discussion of the appendix, Darwin himself posits that the external ear of humans “together with the various folds and prominences…which in the lower animals strengthen and support the ear when erect…is of no distinct use.” Now it is thought that the folded structures of the outer ears reflect sound waves in a manner that helps the auditory system more accurately pinpoint the source of sound in space.

So, it is neither surprising nor unprecedented to discover a previously unknown function for an apparently useless structure. At the same time, such discoveries do not invalidate the more general idea that evolution does sometimes leave in modern species useless vestiges of a formerly complex structure. See this list of the “Top 10″ vestigial organs for examples (a list which includes one vestigial example–the human appendix–but several examples that are true vestiges of structures that disappeared during evolution). Some creationists work strenuously to prove that apparent vestiges actually have functions specified by The Designer (you can see the fruits of their labors in creationist web sites such as Answers in Genesis), and will be greatly reassured by the new paper on the function of the appendix (the same prediction is made here). However, the phenomenon of vestigial structures remains a very conspicuous challenge to a creationist world view, and yet one very easily accommodated by Darwinian theory.

 

‘Deathers’ now!

First (well, recently) the “birther” controversy and now the “death panel” controversy: more debate about the supposedly nefarious aims of Obama and other Democratic politicians that seems to be completely uninfluenced by actual evidence (see previous post). The “deathers” (as I’ve heard them called) find evidence in health reform legislation that the reformists want the government to take over health-care decisions, including whether to to keep grandma on life support, even though (i) no fair reading of the text supports this interpretation, and (ii) the people who wrote it deny having this goal.

The most disturbing aspect of this is that public opinion is being swayed by such incredibly silly arguments.

 

Birthers and evidence

The so-called “Birthers movement” has dominated the news over the past month. In case this posting is read by someone from the distant future–say, a month from now–here’s what this is all about: the birthers claim that President Obama may have been born in Kenya rather than in Hawaii, and hence constitutionally ineligible to serve as President. Although the question was raised during the 2008 primaries by a supporter of Hilary Clinton, it has been embraced by opponents of Obama from the right, and by the crankocracy at large.

This blog is about science, so I’m not going to talk about the history, politics, psychology, sociology or comedy of the birther movement. Instead I want to talk about the role of evidence in this debate, to point out some striking parallels with the role that evidence plays in scientific debates, as well as some striking differences.

So what is the evidence is the birther debate? I’ll keep this brief. Fuller summaries can be found here and here. First, the evidence that Obama is a natural-born citizen of the United States consists of (a) an official “certification of live birth” from the State of Hawaii, (b) statements from current state officials that this document is valid, and (c) announcements of Obama’s 4 August 1961 birth in two Honolulu newspapers. Of these, the first source of evidence is normally regarded as sufficient proof of citizenship.

What about the evidence that Obama was actually born in Kenya? As far as I can tell, only one item of evidence for this claim was put forward to get the birther movement moving. This was a supposed affidavit from Obama’s step-grandmother that she was present when he was born in Kenya. Actually, no such affidavit has been produced to my knowledge. However, there was a recording made of Obama’s grandmother telling one “Bishop Ron McRae” by telephone (with the help of a translator) that she had been present when he was born in Kenya. However, the same interview quickly revealed that she was misunderstood and tried to correct the misunderstanding. Listen to how it unfolded here and here. It sounds to me that when she said she was “present,” she meant to say she was “alive” at the time he was born. In any case, she went on to assert that Obama was born in Hawaii.

That’s it for the primary evidence for either side (unless we were to consider the forged Kenyan birth certificates that were apparently designed to embarrass the birther movement). However, this isn’t the only evidence that has been discussed.

On the birther side, there are numerous claims that are aimed against the evidence of Obama’s U.S. citizenship (not for his supposed Kenyan citizenship). These claims fall mainly into two categories. First there are suggestions that Obama’s Hawaiian documents may be forged or based on false testimony about where he was born. Second, there are allegations (based on faculty legal reasoning) that Obama’s citizenship is called into question by his having only one native-born American parent, or having been adopted by his Indonesian stepfather.

As for the defense of Obama’s status as a natural-born citizen, the additional evidence, such as it is, is mainly along the lines of “why would Hawaiian officials be motivated to lie about the authenticity of Obama’s birth records?” and “why would anyone have a reason to plant false birth announcements in newspapers?”

In other words, the additional evidence being offered by either side consists principally of challenges to the other side’s evidence.

What does this have to do with science? A lot, actually. Science is committed to testing the truth or falsity of claims about nature using evidence publicly available to independent observers. What is the evidence that science uses? By definition it can be any observation made with our unaided senses, or with a device, such as a telescope or microscope, designed to enhance our senses. Such evidence has the power to convince because it is potentially available for anyone check, to replicate. All you have to do is to look with your own eyes, hold the same fossil in your hand, do the same experiment, peer through the same telescope at the right place in the heavens.

So goes the textbook version of how science works. But in practice there is more to it than that; there is an additional kind of evidence that is perhaps more widely used in actual scientific debates than any other kind. I’m talking about testimony, or the trusted statements of reliable observers. As a practical matter, it would be impossible for any one person to repeat all of the observations or experiments that back up the claims of science. So, vast amounts of scientific knowledge are taken on trust. Like almost anyone who has thought about it, I’d love to know what happened to the dinosaurs to cause them to disappear from the face of the earth around 65 million years ago. Actually, I think I do know–not because I or anyone else witnessed the global cataclysm that afflicted the earth 65 million years ago. I haven’t even met the scientists who have evaluated the geological traces left by this cataclysm and have identified the culprit as an asteroid the size of Manhattan island. (Nor have I met the scientists who have suggested instead that the climatic changes that extinguished the dinosaurs were caused by massive volcanic eruptions in what is now India.) I am in no position–practically speaking–to evaluate the evidence for myself. Instead I have to trust someone else’s evaluation of the evidence.

Why should trust in testimony give me such confidence? After all, the latter-day prophet Rael said that he received a message in 1973 from aliens who explained their role in guiding the evolution of life on earth; the not-so-latter-day prophet Joseph Smith said that he received a message in 1823 from an angel called Moroni who told a story little more believable than Rael’s. Lots of people fervently attest to the truth of one or the other of these stories, which amount to eyewitness testimony. I find both to be nonsense. I don’t trust the testimony.

Why, then, do I trust the testimony of other scientists? The key difference is that the testimony of scientists can potentially be checked, and disproven if it is wrong. In fact, the scientific community has developed an elaborate array of social mechanisms to hold scientists accountable for the accuracy of their testimony. These include (i) the expectation that methods be thoroughly described (so others can repeat them), (ii) peer-review of publications, grant proposals, and tenure applications, and (iii) communities of experts who do have the expertise and opportunity to test claims of other scientists independently.

By contrast, the testimony of the prophets and their followers can’t potentially be checked or disproven. All such religious testimony is based on private, rather than public, evidence. The belief system provides no mechanism whatsoever for independently testing such testimony.

Back to the birther “controversy.” The controversy is being kept alive (in some people’s minds) because, after all, it is not hard to poke holes in testimony, if you are creative enough and are willing to impugn people’s motives. So what if there are photographs of an apparently authentic “certification of live birth:” maybe the photographs or the document itself were faked. The Republican governor of Hawaii, backed by other state officials, has attested to the validity of the birth records, but maybe these officials, motivated to defend the pride and integrity of their state, aren’t giving the matter enough scrutiny, or are just lying. The newspaper announcements were real, but perhaps they (along with the birth certificate) were based on false testimony by Obama’s mother, so she could avoid the hassle of going through a naturalization process for her son.

How to counter such criticisms of the testimony? Unfortunately, I don’t see any way to do it. So long as we have to rely upon testimony by people who, rightly or wrongly, can be said to have a motive to lie (or to deceive themselves), then clever critics can poke holes in this testimony. The critics can then satisfy themselves no matter how weak their own evidence.

Common sense provides a way out. Believing that Obama was born in Kenya and not Hawaii entails a belief in a large network of lies, omissions, and misunderstandings, all of which continue to be maintained across generations by people whose motives otherwise would not be aligned. Believing that Obama was born in Hawaii is a much simpler proposition, entailing far less cognitive dissonance.

This kind of common sense has a counterpart in science, the widely used principle of parsimony, sometimes called “Ockham’s Razor” after the 14th century logician William of Ockham. The principle is commonly stated as, “Entities must not be multiplied beyond necessity.” In science this means favoring explanations that account for existing evidence in the most efficient way, i.e., with the fewest auxiliary hypotheses. Scientists use this principle not as a matter of faith, but because it tends to work. Simple example: it is easier to believe that the earth and other planets orbit the sun than that the sun and other planets orbits the earth, because this one elegant hypothesis (presented to western science by Copernicus) more easily explains the apparent motion of other celestial bodies as viewed from earth, including bodies not known prior to the invention of telescopes.

Ockham’s Razor is just a heuristic, a rule of thumb. It isn’t infallible. Sometimes scientific explanations entail hypotheses of great complication, and are nevertheless true. Sometimes there really are political conspiracies involving elaborate webs of deception. But still….

It can be very frustrating to argue with people who cling to conspiracy theories that require a convoluted–and unparsimonious–narrative in which each new fact or item of testimony is met with a counterclaim about a supposed lie or distortion by someone who has no apparent motive to deceive. It is equally frustrating, of course to argue with people who would deny the moon landings, the Nazi Holocaust, or the guilt of Al Qaeda in the 9/11 attacks.

The frustration arises because these kinds of arguments–and those made by the birthers–ultimately don’t have any concern for evidence or parsimony of explanation. Instead they rely upon one underlying assumption: that people lie.