Monday, December 26, 2011

ad hoc hypothesis


In science, an ad hoc hypothesis is an assumption made in response to facts that are inconsistent with a theory in order to prevent the theory from being falsified. By extension, an ad hoc hypothesis is any assumption made to save a claim from being refuted. What are often called ad hoc hypotheses might better be referred to simply as rationalizations.

One of the more important ways of testing a scientific theory is to deduce observations that should occur under specified conditions if the theory is correct. An experiment may create those conditions and if the predicted observations occur, the theory is said to be confirmed. Experiments that confirm a theory should be replicable. If the predicted observations do not occur and it is determined that the theory cannot be correct if they do not, then the theory is falsified. Likewise, if experiments fail to replicate confirmations and it is determined that the theory cannot be correct if replication doesn't occur, then the theory is said to be falsified. If a new fact is discovered that is inconsistent with the theory, the fact must be accommodated. The theory might be tweaked or it may be preserved by hypothesizing another fact that would make the first fact consistent with the theory. Or, the fact might prove the theory false.
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When William Hershel discovered the planet Uranus in 1781 by telescopic observation, it was also discovered that the new planet’s orbit was different from what it should have been according to Newton’s laws. The orbit of Uranus was an anomaly: a phenomenon that apparently did not fit with the Newtonian paradigm. Some scientists may have thrown up their hands and said: “See, Newton was wrong! Hah!” Others may have offered the ad hoc hypothesis that the anomalous orbit was caused directly by God. Uranus has a different kind of orbit than the other planets because God is working a miracle—suspending the laws of nature—perhaps to demonstrate his power and existence to us. But most scientists set to work to solve the puzzle. The simplest solution was to posit another planet beyond the orbit of Uranus whose gravitational force was affecting the planet’s orbit. This hypothesis could be independently tested. Its size and orbit could be calculated based on how much it perturbed the motion of Uranus. Thus was Neptune discovered. When the math for Neptune’s orbit didn’t work in accordance with Newton’s laws, it was proposed that still another planet awaited discovery. The object known as Pluto gave astronomers the data to show that Neptune did, after all, orbit in accordance with Newton’s laws. Both of these hypotheses could be independently tested, albeit with some difficulty given the state of knowledge and technology at the time.
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When Alfred Wegener proposed his theory of continental drift in 1912 against the prevailing theory that the Earth was formed by cooling from a molten state and contractions, he could not explain how continents move. It was suggested that gravity was the force behind the movement of continents, though there was no scientific evidence for this notion. In fact, scientists could and did show that gravity was too weak a force to account for the movement of continents. Alexis du Toit, a defender of Wegener’s theory, argued for radioactive melting of the ocean floor at continental borders as the mechanism by which continents might move. “This ad hoc hypothesis added no increment of plausibility to Wegener’s speculation,” wrote Stephen Jay Gould (Ever Since Darwin. W.W. Norton & Company.1979, p. 163).
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George Dillman claims that he and his top students can knock out people by manipulating some sort of subtle energy called qi (chi or ch'i, pronounced chee). When 8th degree black belt Leon Jay failed to move Luigi Garlaschelli with qi, Dillman offered the following ad hoc hypotheses. 1. Garlaschelli is a total non-believer and you must believe you can be knocked out by qi for the power to work. 2. Garlaschelli might have had one big toe pointing upward and the other pointing downward. If so, the power won't work. 3. Maybe Garlaschelli wasn’t knocked out because his tongue was "in the wrong position."

While Dillman's hypotheses seem like obvious rationalizations, they have the merit of being empirically testable to a degree. Qi remains undetectable by science's most refined measuring instruments, but we can at least test the toe and tongue position claims. If the no-touch knockout doesn't work even when the toes and tongues are aligned the way Dillman wants them, we'll at least know that these hypotheses are false. On the other hand, if Jay or Dillman knocked over Garlaschelli without touching him when his toe and tongue were aligned, we'd have evidence in favor of the qi hypothesis.
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Sunday, December 18, 2011

Natural Thinking: A Case Study

In the concluding chapter of my book Unnatural Acts, I suggest that a good way to enhance critical thinking would be to set a goal of studying various biases, fallacies, and illusions that plague human thinking. I list 59 items worth investigating. I hope this blog will help those choosing to study the 59 items, plus a few more.

After this initial post, the blog will focus on specific cognitive biases, illusions, or fallacies. The next post, for example, will be on ad hoc hypotheses. But I thought I would introduce the blog with a case study that would exemplify the dangers of following intuition and instinct when making judgments. I view Unnatural Acts as an antidote to Malcolm Gladwell's Blink: The Power of Thinking Without Thinking. In Blink, Gladwell argues that intuition or quick judgments can be just as valuable as well thought out and time-consuming evaluations of data. In Unnatural Acts, I try to make the case that while intuition works well enough in many cases, for most important matters there is a much better chance of making a fair and accurate judgment by doing the hard work of collecting, analyzing, and evaluating data in an impersonal, reflective, dispassionate way. Our natural instincts work well enough most of the time, but occasionally we would be better off engaging in some unnatural acts.
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This is a story about a mother trying to understand why her firstborn suffered from a neurological disorder and after a short and miserable existence died soon after his first birthday. It is the story of how a powerful emotional experience affected her judgment to the point where she became unable to see anything good in medicine or anything bad in the anti-vaccination movement. I can't say I have all the details right, but the general picture is clear enough from what information is available about the case.

Stephanie Messenger says she wrote the children's book Melanie's Marvelous Measles because vaccinations are ineffective, children should be taught to embrace childhood disease, and getting a disease like measles helps build the immune system naturally. Messenger explains her reasoning on her website Nature Matters!, which she runs out of Queensland, Australia.

She tells us that she had her first child vaccinated twice by the time he was four months old. In the U.S., the recommended vaccine schedule would include immunization against about a half dozen diseases during an infant's first four months. Messenger writes of the initial vaccination for her son:

Within moments of my son receiving his immunisations he was screaming. This continued for most of the day and when he wasn't screaming he was crying. This was unusual as he was a very happy, placid baby, who was already rolling over at 8 weeks and gooing and gahing at the first sight of his mother. The doctor told me his reactions were 'normal' and he'd be OK in a couple of days.

After the first day he had almost recovered with only some irritability and restlessness noticeable. As the weeks passed he continued to reach milestones and all appeared OK.

It would appear that her doctor was right. The infant stopped fussing and "continued to reach milestones." Then he had his second round of immunization:

At 4 months of age I dutifully took him for his next round of vaccinations. This time he screamed louder and I could not console him at all. I would breastfeed him, only to have him projectile vomit it back up and still the screaming continued. He had never before vomited at all, ever. After he had vomited 2 feeds I called the doctor and told her what was happening and she said to stop breastfeeding and give him juice only. He kept some of it down but still vomited often.

The next day I called the doctor and told her I think the vaccines have done this and she told me 'no, it's just a coincidence' but to bring him back in, which I did. She referred me to a specialist. While waiting for the specialist appointment in a few days, my baby boy started doing strange things. He started arching his back and crying out in pain. He was as stiff as a board. His eyes would roll into the back of his head. He didn't have a temperature. He had also started shuddering but he wasn't cold. (I later learnt from the doctor these were convulsions and seizures). The vomiting continued and I was convinced to give up breastfeeding by the clinic sister. He vomited up the formula also. I was getting very scared.

Messenger doesn't say why she thought the vaccines had made her infant sick. She may have been influenced by the anti-vaccination movement in Australia and elsewhere. She may have been influenced by seeing Dr. Robert S. Mendelsohn on the Phil Donahue show talking about the dangers of vaccination. In any case, her early judgment that vaccines caused her son's convulsions and other problems was not based on scientific evidence. All she knew for sure at that point was that the infant showed signs of illness shortly after his vaccinations. Whatever the trigger, her initial judgment about the cause of her son's seizures wasn't based on research she had done. The research would come later. To her credit, she was skeptical of her doctor's assurance that the connection between the vaccinations and the convulsions was coincidental. She was not afraid to challenge the medical community. She would not blindly accept what the health experts had to say about the value and safety of vaccinations. She set out to do her own research. That's an admirable trait and is to be commended.