Archive for May, 2007

May 09 2007

Probability and Incredulity

From time to time I will explore in depth a particular logical fallacy. Logic is a common theme in this NeuroLogica blog, and a finely tuned understanding of logic both valid and fallacious is essential to critical thinking. But fallacious logic is not always simple to understand and apply to the real world, so it is helpful discuss examples and applications. I claim no expertise in logic, I just like to use it as often as possible, and it’s kind of hard to avoid being an active skeptic. Today’s fallacy is the argument from personal incredulity.

The essence of this fallacy is the argument that a particular claim is not true because it is difficult to imagine, understand, or believe. What I consider to be a subset of this fallacy is the argument from ridicule – that something is wrong because it is ridiculous.
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May 08 2007

Is the Brain Analog or Digital?

Published by under Neuroscience

A reader sent me the following questions:

“On your recent blog entry about the virtual simulation of the mouse brain, you said that the human brain is analog, not digital. I thought that the firing of a neuron was a digital process- it either fires or it doesn’t. I was under the impression that the strength of a signal is irrelevant once an action potential is generated. Is this not true? Does the intensity of a signal affect future syntactic connections?

“As a system, the human brain is definitely analog, as it produces different firing patterns (outputs) when the same stimuli (inputs) are presented to it. I’m just wondering whether the more basic level of neurons would be considered analog or digital.”

– Jordan Horowitz

This is an interesting question and provides an opportunity to explore some of the basics of the anatomy of neuronal connections. It is true that the firing of a neuron (conducting a signal from the cell body down its axon and ultimately synapse on another neuron or end organ) is all or none – a neuron cannot fire a little or a lot, it just fires. This would seem to make neuronal function digital, since it is a binary on/off phenomenon. However, there are three important reasons why this is ultimately not the case.

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May 07 2007

I’m Certain You’re Going to Love This One

“Certainty? In this world nothing is certain but death and taxes.” – Benjamin Franklin

“What men really want is not knowledge but certainty.” – Bertrand Russell

“The quest for certainty blocks the search for meaning. Uncertainty is the very condition to impel man to unfold his powers.” – Erich Fromm

“Doubt is not a pleasant condition, but certainty is absurd.” – Voltaire

“Fear comes from uncertainty. When we are absolutely certain, whether of our worth or worthlessness, we are almost impervious to fear.” – William Congreve

Let me add my own quotable quote concerning certainty: The certainty that one is correct is the most reliable predictor of error, for knowledge stems from scientific methodology and certainty is anathema to such inquiry.

Recently I wrote about the general methodological differences between skeptics and believers. I did not touch upon the notion of certainty, but this is an absolutely critical distinction, and is a common theme behind many pseudoscientific beliefs. A good scientific skeptic must learn to be comfortable with doubt. In fact the very process of skepticism begins and ends with doubt. The methods of good scientific investigation stem from systematically doubting everything we think we know and every step in a chain of evidence or argument. Scientists know that all conclusions in science are tentative – that is just another way of talking about the central role of doubt and uncertainty in science.

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May 04 2007

Filling the Gulf

Most skeptics will eventually get into a discussion with a “true believer” or proponent of the paranormal. The experience is often highly frustrating, because, in my experience, either one or both sides fall into the trap of dismissing the conclusions of the other based upon self-serving assumptions. There is a wide gulf between skeptics and believers, and more often than not the gulf is too wide to make a connection.

What I find most frustrating is that both sides are looking at the same body of evidence, and have access to the same fund of accumulated scientific knowledge (sometimes), and yet they come to opposite conclusions. There therefore must be one or more critical differences between the methods of skeptics and those of believers. Discussions should therefore focus on identifying those differences, rather than the psychology of why someone believes or does not believe. Psychological speculations may be interesting, but they are completely counterproductive to finding common ground.

In my experience the two sides are not equal in this flaw. I freely admit my bias as a skeptic, but even taking this into account I find that the vast majority of believers make no or little attempt to truly understand the position of the skeptic, while skeptics (at least those who are experienced and mature) have gone to great lengths to identify in detail the flaws in the methodology of the believers. But let me explore the manner of dismissiveness on both sides.

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May 02 2007

Modern Medicine and Evolution

I was recently e-mailed the following question:

Is there any risk that modern medicine is diluting the strength and stability of human beings by essentially taking natural selection out of the picture? By entertaining a desire to prolong individual lives, are we propagating genetic weaknesses (“weaknesses” in the Darwinian sense) that could ultimately lead to the demise of humanity, or is that such a potentially lengthy process that humanity as we know it will likely have evolved into something new or become otherwise extinct before that could ever occur? I hope you understand that I am not necessarily advocating that we allow people with genetic weaknesses to die so that they might not procreate and dilute my gene pool. I was just wondering if there’s any validity to this thought.

This is a common question and the answer has several components.

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May 01 2007

Another Salvo in the Mercury/Autism Controversy

Published by under Neuroscience

There are many true controversies within science – where the evidence is not definitive competing theories may remain plausible and their proponents will fight hard for them. Ideally, this scientific fighting will lead to new ideas and new evidence that will eventually resolve the controversy. But most of the scientific controversies that garner public attention are fake controversies – they are not disagreements among serious scientists but between the mainstream scientific consensus and a dedicated group of unscientific ideologues working hard to subvert science to their cause. Evolution vs creationism is a good example of such a fake controversy, as is the denial that HIV causes AIDS. Another is the controversy over whether or not mercury, and specifically the mercury-containing vaccine preservative thimerosal, causes autism. The scientific consensus forming around a large body of evidence is pretty solid – no! Vaccines do not cause autism.

Yet there exists a largely grassroots movement that insists mercury/thimerosal does cause autism. Their beliefs are born largely by desperation, as the ranks of such groups are filled by parents of ASD children. They are ideologically fueled by anti-establishment, anti-government, and anti-corporate conspiracy thinking. They have their champions in the guise of activists like Robert Kennedy, journalists like David Kirby, and rogue scientists like the father and son Geier team.
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