Anecdotal (testimonial) Evidence

via The Skeptic’s Dictionary

Testimonials and vivid anecdotes are one of the most popular and convincing forms of evidence presented for beliefs in the supernatural, paranormal, and pseudoscientific. Nevertheless, testimonials and anecdotes in such matters are of little value in establishing the probability of the claims they are put forth to support. Sincere and vivid accounts of one’s encounter with an angel or the Virgin Mary, an alien, a ghost, a Bigfoot, a child claiming to have lived before, purple auras around dying patients, a miraculous dowser, a levitating guru, or a psychic surgeon are of little value in establishing the reasonableness of believing in such matters.

Anecdotes are unreliable for various reasons. Stories are prone to contamination by beliefs, later experiences, feedback, selective attention to details, and so on. Most stories get distorted in the telling and the retelling. Events get exaggerated. Time sequences get confused. Details get muddled. Memories are imperfect and selective; they are often filled in after the fact. People misinterpret their experiences. Experiences are conditioned by biases, memories, and beliefs, so people’s perceptions might not be accurate. Most people aren’t expecting to be deceived, so they may not be aware of deceptions that others might engage in. Some people make up stories. Some stories are delusions. Sometimes events are inappropriately deemed psychic simply because they seem improbable when they might not be that improbable after all. In short, anecdotes are inherently problematic and are usually impossible to test for accuracy.

Thus, stories of personal experience with paranormal or supernatural events have little scientific value. If others cannot experience the same thing under the same conditions, then there will be no way to verify the experience. If there is no way to test the claim made, then there will be no way to tell if the experience was interpreted correctly. If others can experience the same thing, then it is possible to make a test of the testimonial and determine whether the claim based on it is worthy of belief. As parapsychologist Charles Tart once said after reporting an anecdote of a possibly paranormal event: “Let’s take this into the laboratory, where we can know exactly what conditions were. We don’t have to hear a story told years later and hope that it was accurate.” Dean Radin also noted that anecdotes aren’t good proof of the paranormal because memory “is much more fallible than most people think” and eyewitness testimony “is easily distorted” (Radin 1997: 32).

Testimonials regarding paranormal experiences are of little use to science because selective thinking and self-deception must be controlled for in scientific observations. Most psychics and dowsers, for example, do not even realize that they need to do controlled tests of their powers to rule out the possibility that they are deceiving themselves. They are satisfied that their experiences provide them with enough positive feedback to justify the belief in their paranormal abilities. Controlled tests of psychics and dowsers would prove once and for all that they are not being selective in their evidence gathering. It is common for such people to remember their apparent successes and ignore or underplay their failures. Controlled tests can also determine whether other factors such as cheating might be involved.

If such testimonials are scientifically worthless, why are they so popular and why are they so convincing? There are several reasons.

MORE . . .

Here is a great podcast:

Robert T. Carroll, Ph.D. discusses anecdotal evidence (8 minutes).

Click here to open in a new window or listen right here:

Via Skepticality – the official podcast of Skeptic magazine and the Skeptic Society

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