The role of cognitive bias in the existence of crackpottery and quackery

A few recent articles got me thinking about the prevalence of crackpot science and medical quackery in modern society, and I thought I’d just write a post with some general thoughts and observations on the subject.

The articles that got me thinking again: McCain jumps into autism controversy, rejects science and evidence, via The Carpetbagger Report, the ‘return’ of the Lizard Man in Lee County, South Carolina, and Bad Statistical Reasoning about Weather and Climate, via Good Math/Bad Math.

Let me summarize each of these reports briefly after the fold, and then speculate what they (and other unscientific arguments) have in common.

Let’s first look at John McCain. As a town hall meeting in Texas, McCain responded to the question of a mother with an autistic child:

McCain said, per ABC News’ Bret Hovell, that “It’s indisputable that (autism) is on the rise amongst children, the question is what’s causing it. And we go back and forth and there’s strong evidence that indicates that it’s got to do with a preservative in vaccines.”

McCain is, to put it quite bluntly, wrong. There is no scientific evidence linking the presence of thimerosal in childhood vaccines to the rise in U.S. autism cases, and even if there is a small causal effect it is far dwarfed by the very real risk of not vaccinating children against deadly communicable diseases. In fact, the preservative hasn’t been used in vaccines since 2001, and autism is still as rampant as ever, but this belief in a connection persists.

In Lee County, SC, an elderly couple awoke one morning to find their car damaged and their pets missing, and immediately suspected the actions of a mythical ‘lizard man’ which had first been reported in 1988. They came to this conclusion even though there was nothing ‘lizard-y’ about the crime scene: no scales, no lizard-prints, and no evidence that a lizard man ever existed, anywhere.

Mark Chu-Carroll noted one of his pet peeves about the global warming debate, a flawed argument used on both sides of the debate:

The basic argument takes one of two forms:

  1. Wow, look how hot it is today! How can anyone possible deny global warming?
  2. Wow, look how cold it is today! How can those idiots believe in global warming?

These statements are flawed scientifically because a single day’s weather does not say anything about overall climate change, but people still make them all the time.

I’ve been fascinated by this sort of flawed thinking for years, and all of it can be broadly traced back to what psychologists would call ‘cognitive bias.’ In particular, I would say that most of it falls under the category of ‘confirmation bias‘: “a tendency to search for or interpret new information in a way that confirms one’s preconceptions and avoids information and interpretations which contradict prior beliefs.” In simpler terms, you remember the things you agree with and forget the things you disagree with.

To see how this works, let’s look at a specific example of ESP (extra-sensory perception). Suppose you consciously make a prediction of a future event. If you are correct in your prediction, you will most likely remember it, at the very least because it’s a good story to tell. If you are wrong in your prediction, however, you will quickly forget you ever made it. After many such attempts at ESP, you will probably accumulate a large memory of ‘correct’ predictions, possibly leading you to conclude that you’re psychic, but you’ll have forgotten the even larger number of times you guessed wrong. This ‘selective memory’ leads you to a conclusion which is at odds with reality, and can potentially have harmful consequences if acted on.

Mark Chu-Carroll’s pet peeve about global warming is a simple example of this bias. If you’re a believer of global warming, you’re more likely to pay attention to those days when it is anomalously hot outside as a confirmation of your beliefs. If you’re a global warming denialist, you’re more likely to note the extremely cold days. (Note: global warming is on firm scientific footing! The denialists have come to the wrong conclusions, but both the pro- and con- arguments mentioned above are flawed.)

People are often biased towards personal stories and anecdotal evidence over hard scientific facts. In the anti-vaccination crusade, people are moved by the tales of children who received vaccinations and then were diagnosed with autism. The fact that the vast majority of vaccinated children turn out just fine is ignored in favor of believing the heart-wrenching (and usually sincere) tales of family tragedy.

In the lizard man case, local legend has trumped, in the minds of the residents of Lee County, common sense explanations of what chewed on the couples’ car. In pretty much any other county in the country, people would be looking for a stray bear, mountain lion or coyote; in Lee County, the evidence ‘points’, in their minds, to the utterly ridiculous idea of a hitherto undiscovered lizard man.

Science itself is not immune to problems of selection or confirmation bias: I remember a case a number of years ago in which a nuclear research lab was getting good evidence for an exotic nuclear state. Later evidence suggested that the researchers were tossing out ‘noisy’ data and keeping the data which looked good, which served to artificially enhance a nonexistent signal. The scientific method, however, including peer-review, is designed to detect, block and weed out such bias in research.

Do I have a point to this post? Not particularly; I’m really just thinking out loud about some news of the week. I guess, if anything, this is a warning to scientists and non-scientists alike to make certain the conclusions follow the data, and not the other way around.

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2 Responses to The role of cognitive bias in the existence of crackpottery and quackery

  1. Personal Demon says:

    On the topic of the climate change debate, the folks over at have performed a literature survey of all the climate change papers published in the 1970s and come to the conclusion that only 7 out of the 71 peer-reviewed papers predicted that the Earth was entering a new Ice Age. Sixty-Two percent of the papers were predicting global warming due to increased greenhouse gases. This hasn’t stopped global warming critics from characterizing “global cooling” as the majority opinion, and then using this straw man argument to pillory environmental science as a whole. I haven’t read the “ice age” papers, so I would be way out of line if I accused those authors of “cognitive bias” (when the issue could just as easily be attributed to improved measurements over the past three decades). That being said, it was certainly true that the 1970s was a colder than average decade, and that led many people to conclude that it was the beginning of a trend.

  2. PD: That’s an interesting result, and it doesn’t really surprise me. I wouldn’t claim that the authors of the papers were guilty of such a bias as much as the media: I still remember, from my youth, breathless stories on the news programs predicting a new Ice Age and what it would entail for humanity. I’m guessing that a few studies produced cooling results, and that was exciting and different (‘man bites dog’) and therefore got more attention than the warming research (‘dog bites man’ – boring!).

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