[extropy-chat] FWD [forteana] Perceptual-blindness experiments (fwd)

Terry W. Colvin fortean1 at mindspring.com
Fri Feb 27 16:40:30 UTC 2004

---------- Forwarded message ----------

I've been very interested in human perception and information processing
for many years now. Our brains are pretty flakey even on a good day
(half-assed may be 1/4 ass too positive?), and the slightest change in
chemistry brought on by stress, drugs, diet, disease, etc., can totally
alter how we perceive the world around us.

Which is why eyewitnesses are so suspect in criminal investigations.
Police prefer to never base any arrest totally on an eyewitness without
any supporting physical evidence simply because the eyewitness is almost
always wrong about much of what they think they saw.

So I love these kind of experiments.

< http://viscog.beckman.uiuc.edu/media/sciam.html >

Here's how it works. There's a one-minute video of two teams, each with
3 players. One team has white shirts and one team has black shirts.
They're tossing around 2 basketballs. The subject's task is to count the
number of passes made by the white team. About 35 seconds into the
video, a guy dressed in a gorilla outfit enters the mix, beats his chest
for about 9 seconds and then leaves.

When people do this test, the results are that 50% never see the gorilla
guy. Yep, 50%. Doesn't mater who you test. Out of any group of people,
50% will concentrate so hard on watching the basketballs that they don't
see anything else in the film.

The effect is called inattentional-blindness. It probably happens
because (1) visual perception does not work like a camera. We "see" what
our brains process, not what our eyes see. (2) heavy concentration on
one thing requires enough brain resources that there's not much left
over for other tasks. (3) we tend to see what we expect to see, not
what's really there.

None of this is a problem when you have lots of time, it's only a
problem when you have no more than a few seconds to perceive and
interpret some unusual event.

Good stuff for a novel. Character commits a crime in such a way that
half the witnesses don't even see him do it. Police are stumped because
half the witnesses say one thing, half say another, and ALL can pass lie
detector tests. [Lie detectors don't test whether you're lying. They
test whether you feel guiltily about lying. If you're wrong but think
you're telling the truth, you zip right through the test.]

The difficult part, as with much fiction, is convincing readers that
such a bizarre but true effect is really true and not the made-up part
of the story. 8-)

"Only a zit on the wart on the heinie of progress." Copyright 1992, Frank Rice

Terry W. Colvin, Sierra Vista, Arizona (USA) < fortean1 at mindspring.com >
     Alternate: < fortean1 at msn.com >
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