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Eyewitness testimony/anecdotal evidence: Why is this bad evidence?

What makes a claim extraordinary?

Why does that claim require extraordinary evidence?

What is extraordinary evidence?


Why is the claim,
"I saw an alien spacecraft hovering over my house last night" extraordinary?

Why is the claim "I saw Dan at the store today" not extraordinary?


Just more questions non-skeptics might ask. :)

See my post above:

When a person makes a statement about an event that does not fit within the body of knowledge that science has thus far accumulated...
 
What makes a claim extraordinary?


The consequences of it's truthfulness.

If a claim would overturn a major tenet of science, then it would be extraordinary.


Why does that claim require extraordinary evidence?


In order to avoid mistakenly rewriting all of our knowledge to date.


What is extraordinary evidence?


White House lawn. Klaatu barada nikto. Or similar.


Why is the claim,

"I saw an alien spacecraft hovering over my house last night" extraordinary?


The claim is quite common. If it were true, it would be the first time, and that would be extraordinary.


Why is the claim "I saw Dan at the store today" not extraordinary?


It might be, if Dan has been dead for six months.

Realistically though, it's back to consequences. Most people willl respond to the claim with "So what?"


Just more questions non-skeptics might ask. :)


Yup :)
 
What makes a claim extraordinary?

Something that deals with the paranormal, to start. If I told you that I'm fostering a kitten named Peppercorn you would probably believe me. Fostering a kitten is a believable and normal thing to do. If I said that Peppercorn knows how to talk and can hold a great conversation about Chaucer, then this claim would become extraordinary. Cats don't converse in English and even if they did, I doubt they'd want to talk about Chaucer.

Why does that claim require extraordinary evidence?

The evidence has to match the claim. If I told you that Peppercorn can talk then sent you a video of her meowing you would not be convinced that she can actually talk.

Why is the claim,
"I saw an alien spacecraft hovering over my house last night" extraordinary?

Why is the claim "I saw Dan at the store today" not extraordinary?

We see people at the store all the time. Running into someone you know in your hometown is not extraordinary. However, as of yet, there is no credible, verifiable evidence that UFOs exist. The event in itself would be extraordinary.

Just more questions non-skeptics might ask. :)
 
Most people who have served on juries and who have listened to conflicting eyewitness testimony know that what people think they are sure about--and what they will swear to--must be mistakes. Once I was a juror on an assault case. The defendant (charged with assaulting a co-worker in the parking lot of their place of work) did not testify, but the plaintiff, the parking-lot attendant, and a security guard all did.

The plaintiff said the defendant had attacked him with a hammer taken from their place of employment (which meant that the attack was premeditated, not a spur-of the moment thing).

The attendant said the defendant had picked up a broken-off wing mirror from a car as he ran after the plaintiff and that he hit him with that.

The security guard said he saw the defendant running away from the parking lot, holding what he thought was a gun.

Two of these witnesses (and maybe all three) had to be wrong.
 
Something that deals with the paranormal, to start. If I told you that I'm fostering a kitten named Peppercorn you would probably believe me. Fostering a kitten is a believable and normal thing to do. If I said that Peppercorn knows how to talk and can hold a great conversation about Chaucer, then this claim would become extraordinary. Cats don't converse in English and even if they did, I doubt they'd want to talk about Chaucer.


Well, maybe just a brief chat.


Thou seydest this, that I was lyk a cat;
For whoso wolde senge a cattes skyn,
Thanne wolde the cat wel dwellen in his in.
And if the cattes skyn be slyk and gay,
She wol nat dwelle in house half a day,

But forth she wole, er any day be dawed,
To shewe hir skyn, and goon a caterwawed.
This is to seye, if I be gay, sire shrewe,
I wol renne out, my borel for to shewe.
Sire olde fool, what eyleth thee to spyen.


- Geoffrey Chaucer​
 
If they missed the gorilla, if anything, that's a positive thing. It means they were concentrating on what they'd been designated to do wrt the exercise, i.e. counting the number of times the ball was passed.
I'd guess the people most likely to notice the gorilla were the ones not giving much of a stuff about the counting.

:eek::covereyes
 
Multiple eyewitnesses may not be reliable either. Ask supporters of opposing teams to describe a contentious penalty decision.
 
If they missed the gorilla, if anything, that's a positive thing.

Positive for what?




It means they were concentrating on what they'd been designated to do wrt the exercise, i.e. counting the number of times the ball was passed.
I'd guess the people most likely to notice the gorilla were the ones not giving much of a stuff about the counting.

Yes, that's the point. Most 'eyewitnesses' are asked to tell us about something that happened when they were going about their business concentrating on something else.

I've never heard of somebody testifying, say, that they're confident in what happened during the car accident, because they got in the car to make detailed notes about crashing it.

In any case, there's abundant evidence that even people asked to concentrate on an activity will not be reliable. (a good parallel test would be to see if there's consistency on the number of ball passes recalled for the video, too)

Another example of distraction is the 'interrupted lecture' experiment where students are asked to fill out a crime report after the lecture is interrupted by an attack on the prof. It was a staple in second year psych.
 
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I don't think we are poor encoders of the information. I bet that every detail you paid attention to regarding the car accident is stored in your memory somewhere. The problem is survival depends less on memorizing and time stamping a verbatim account of an incident then it does integrating the incident with everything else you know. Witnessing and trying to make sense of a car accident would pull in other memories of perhaps similar incidents or at least common knowledge.

Remembering what happened 2 years later in court is hard because we've got the original memory plus excess baggage, including times you thought about the accident or were interviewed about it. It's a retrieval problem, and I think it illustrates just how awesome human memory is for making sense of the world (versus remembering what you had for breakfast 22 days ago).
 
Unless you believe that all anecdotal evidence is accurate, how do you decide which to believe and which to discard?

~~ Paul
That's a toughie, but if, say, the town drunk tells me he took a ride in a flying saucer last night, I tend to think that's a tad less credible than if a Ph.D. astronomer tells me that he saw something in the sky last night that he can't explain.
 
Positive for what?
Positive in the sense that the clear intent of the people performing that experiment was to write your average Joe off as an inattentive idiot.
Yet they didn't really think through their experiment too well; so the joke's on the 'scientists' rather than the subjects they're wishing to patronise.
All positive, that.

Yes, that's the point. Most 'eyewitnesses' are asked to tell us about something that happened when they were going about their business concentrating on something else.
Really? Got anything to back that up?
I imagine you're talking about witnessing crimes or disasters, or serious accidents and things of that nature, things of real import. When people notice this stuff they tend to give it a lot more attention than their usual hum-drum dodging-people-on-the-sidewalk behaviour, which they can do pretty much automatically.

I've never heard of somebody testifying, say, that they're confident in what happened during the car accident, because they got in the car to make detailed notes about crashing it.
No idea what you're talking about.

In any case, there's abundant evidence that even people asked to concentrate on an activity will not be reliable.
Which, if true, undermines all human knowledge, ..thus undermining the claim itself and making it impossible.. or at least making it open to the same accusation.. thus pointless.

(a good parallel test would be to see if there's consistency on the number of ball passes recalled for the video, too)
I imagine it'd be a bell curve, as are many other 'scientific' results we trust.

Another example of distraction is the 'interrupted lecture' experiment where students are asked to fill out a crime report after the lecture is interrupted by an attack on the prof. It was a staple in second year psych.
What is this unreliability of human experience tested against?
It can only be tested against other human experience.

In the end, undermining the validity of human experience becomes a self-defeating exercise.
Of course, those seeking to use this approach do it unevenly.. e.g. somewhere like here you'll see that the experiences of a few people simultaneously witnessing the same UFO or ghost will have this argument used against them, while a few scientists simultaneously experiencing a particular experiment will not.
 
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Unless you believe that all anecdotal evidence is accurate, how do you decide which to believe and which to discard?

~~ Paul

Well, as I understand it in a jurisprudence setting (that's what I get for dating lawyers ;)), eyewitness testimony is only part of the package. I saw him rob the bank; she saw him rob the bank; they saw him rob the bank, his fingerprints were there, his DNA was there, his alibi doesn't check out, the people who say they saw him are cross-examined, and through the adversarial justice system, things get settled one way or the other. The eyewitness testimony is questioned and examined and given the most skeptical treatment possible very extensively. One side is arguing against it passionately and presenting all evidence to discredit it. So that's the huge difference between eyewitness testimony in a court system and in a situation where someone's supposedly seen something "paranormal."

Then there's the issue of medical case studies based on a single person. The problem here is that we do see a lot of weird medical claims (strange allergies, some bizarre substance being the cure for everything, vaccines causing autism, psychic surgery, we don't need to go through the whole list), and their claimed success is always based on dramatic improvement in individual cases. But there's a world of difference between these anecdotes and actual case studies. A good example is when one patient may have a reaction to a particular medication that's never been recorded before. This would be reported (probably by this person's doctor), and written up in a peer-reviewed journal. The author might have a hypothesis as to why this reaction happened, but it must be based on information already available. If it's a legitimate case study, others will come in to support it, the mechanism can be studied, and conclusions can be drawn. This is exactly what happened with the issue of certain fruits that absolutely should not be eaten with some very common drugs (Tegretol, the statins, and Seroquel being the main offenders.) Unfortunately, this information hasn't made its way down to the general public very well yet.

But evidence based on something that comes from a single individual doesn't work this way when applied to situations where paranormal claims are involved. So I don't think that the issue is just the way that the claim that's being made; a lot of it has to do with the type of claim that's being made. I would probably be just as suspicious of a study supposedly proving aliens that was promoted as double-blind and run by distinguished researchers.
 
In the case of our hypothetical auto accident, a trained investigator will look at the damage to the cars, damage to any objects at the scene, distribution of debris and tire marks from the vehicles, and testimony from any non-involved witnesses as well.

Usually, I can figure out what happened with a glance at the autos.

In police work, we are well aware that people, especially under stress, are often very poor witnesses. Especially if they are personally under stress; a news segment just aired locally about a string of armed robberies. A couple of victims were able to describe the robber's gun pretty well, but not the robber....They were fixated on the weapon.
Often, a non-involved witness will provide more detail.
 

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