Skepfeeds-The Best Skeptical blogs of the day

Anectodal Evidence – a refresher

Posted in Skepdude by Skepdude on May 21, 2009

We all know that anecdotal evidence does not constitute proof of anything, except a belief that a person, or persons, are holding for one reason or another.  Many pseudo-scientific fields employ the anecdotal evidence tool because it can be evoke powerful emotional reactions from people. Autism “alternative medicine” is not an exception. Here is your typical anectode from the parent’s of an autistic child who improved, due to a radical change in his diet…according to the parents.

To watch Harry Weaver color with his grandmother, you’d assume he’s like any other three-year-old. That was not the case a year ago.

“You could call his name and he wouldn’t respond to his own name.  You could go clap your hands behind his head and he would act like nothing happened.  Somebody could walk up and say “boo,” and he would go on about his business just doing what he was doing,” says Julie Weaver.

“He was doing the traditional route and it wasn’t working. It wasn’t working. I had to do something else. I was losing more of him every day,” says Weaver.

So Julie radically changed Harry’s diet. She took out foods that contained gluten, a wheat protein from flour, and casein, the milk protein in cow’s milk.

She said she saw an immediate difference, describing it as a fog being lifted from Harry’s eyes.“He entered our world. He started having meaningful speech.

He would point his finger to show us what he wanted now. And when the therapist would come to the house to do therapy, he would cooperate,” says Weaver.

First, I am glad this child was able to overcome some of the troubles autism brings to kids. But I can’t help but note the fact that when the new diet was implemented, the regular therapy continued. It is impossible to reject the hypothesis that the continued therapy finally started showing some results. This is a typical post hoc ergo propter hoc fallacy, one that no person alive is immune from, including your own. We naturally like to see patterns like this, and if it makes us feel like we figured out how to solve the problem, we tend to see the correlation even more, even when maybe it is not there.

Is anyone aware of any studies done about diet change and autism? Please let me know in the comments.

How Anecdotal Evidence Can Undermine Scientific Results

Posted in General Science, Medicine by Skepdude on August 2, 2008

The recent medical controversy over whether vaccinations cause autism reveals a habit of human cognition—thinking anecdotally comes naturally, whereas thinking scientifically does not.

On the one side are scientists who have been unable to find any causal link between the symptoms of autism and the vaccine preservative thimerosal, which in the body breaks down into ethylmercury, the culprit du jour for autism’s cause. On the other side are parents who noticed that shortly after having their children vaccinated autistic symptoms began to appear. These anecdotal associations are so powerful that they cause people to ignore contrary evidence: ethylmercury is expelled from the body quickly (unlike its chemical cousin methylmercury) and therefore cannot accumulate in the brain long enough to cause damage. And in any case, autism continues to be diagnosed in children born after thimerosal was removed from most vaccines in 1999; today trace amounts exist in only a few.

Read the rest of Michael Shermer’s article at Scientific American.