Bad Witness! No Cookie!

March 21, 2011

We’ve been trained for a very long time that an eyewitness is a very reliable source of information.  Often times an eyewitness at a trial can be the difference between a conviction and acquittal.  And if one witness is good, many witnesses is better.

The problem is, witnesses are a very poor source of information and whole crowds of witnesses are not much better.  Our senses, primarily sight and sound, are not perfect and our brains are very adept at filling in the blanks. When it comes to memory, we don’t fair much better as there too our brains tend to make up stuff.

A picture that has nothing to do with the article.

This is going to be a very important concept in future blog posts, so I figured I better cover it early.  So much of critical thinking centers around knowing what information to believe and what not to believe.  But for now, read this and let it sink in.  It’ll be important later.

Let’s start with memory.  Basically, you suck at memory.  Not only do you forget things, but you make stuff up and convince yourself that you got it right.  Our brains need to make sense out of everything.  If we experience something that doesn’t make sense our brains will frequently make things up in order to bring sense to our reality.  Check out this Scam School video.  In this video, Brian Brushwood demonstrates this effect.  It’s worth the 5 minutes to watch, and be sure to play along with the game.  Get your #2 pencil and paper ready!  Watch the video before reading on.

(As an aside, here are two more videos from Brian Brushwood.  At 40 minutes each these videos are a little long.  But they very entertaining, and will leave you wondering how humans ever got out of the stone age. )

So let’s say that an eyewitness was on the stand at a trial.  Can you trust their statements? Maybe, maybe not.  It’s a hard thing to judge, but you certainly can’t assume it’s true.  Here’s a transcript of a presentation by a Law and Psychology professors over at the Stanford Law School that covers the details much better than I could.

Now, on to eyesight.  Our eyes are bad, very bad.  We are especially bad at estimating size and distance.  And when things are fuzzy or dim we tend to make up detail that isn’t there.  The easiest example of this is your typical “UFO” sighting.  Here’s a great write-up about the October 2010 UFO sighting in New York.  The video embedded in that page is no longer valid, but this one still works.   I laughed when the reporter describes Jupiter as “having a tail and blue flashing lights”.

Most of our visual mistakes are made when looking up into the sky.  If you see a dot in a cloudless sky you have no frame of reference to compare it with.  You can’t tell if it’s a 1/2 mile wide balloon 20 miles away, or a 12 inch balloon 40 feet away.  Even if there were clouds you’d still have issues because you don’t really know how far away the clouds are, or how big they are.

We also make up detail that isn’t there.  In the late 1800’s and early 1900’s many people thought that there were canals on Mars.  The main proponent of this was Percival Lowell.  Lowell was an otherwise remarkable astronomer but fell prey to an imaginative mind and a fuzzy telescope image.   And don’t even get me started on the Face on Mars!

I know what you’re thinking. “Did he fire six shots or only five?” Well, to tell you the truth, in all this excitement I kind of lost track myself. But being as this is a .44 Magnum, the most powerful handgun in the world, and would blow your head clean off, you’ve got to ask yourself one question: Do I feel lucky? Well, do ya, punk?

The evidence is not quite so clear when it comes to hearing.  Mostly there just have not been as many studies into the accuracy of our ears and how our brain processes what we hear.  We certainly have a hard time counting events, like gun shots, that happen quickly.  I can also tell you that, as someone who has ran the sound system for lots of events, the volume of a sound will also effect your perception of pitch.  Our ears do degrade age.  And sometimes sound does not behave in an intuitive way.   The end result is that, like memory and eyesight, our hearing cannot be completely trusted either.

One topic which I won’t get into this time is our brain’s tendency to find patterns where a pattern does not exist.  That could be a whole series of blog posts by itself!

So what does this all mean?   Simply put, it means that we have to be mentally vigilant and identify ways that our senses and brain fail us.  We must take these into account when weighing evidence, anecdotes, and eyewitness testimony.  Later blog posts will cover things like the Scientific Method, which is simply a methodology to keep our brain from getting in the way of logic and reason.



  1. This explains why when I worked in retail, and men would come through to purchase clothing for their wives/girlfriends/mistresses, when asked the woman’s size men would invariably reply “she’s about your size”. Two weeks later, I’d see the woman who was “about my size” come in to return the mis-sized gift.

  2. My memory says I hallucinated this blog post.

  3. […] Kessner's Soapbox My personal soapbox to rant about whatever is on my mind. « Bad Witness! No Cookie! Followup to Bad Witness, No Cookie! March 25, 2011 I ran across this news item today and […]

  4. […] to prove a hypothesis in a way that’s immune from human interference.  In a previous post, Bad Witness! No Cookie!, I talked about how the human brain and senses can mess with what we think is the truth.  This […]

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