[PLUG-TALK] A 5 bit interrogation

Keith Lofstrom keithl at kl-ic.com
Wed Aug 3 13:17:03 PDT 2016

Devotees of ancient television shows might remember the
surreal 1967-1968 British science-fiction/mystery/drama,
"The Prisoner".  

In James V. Stone's fascinating 2012 book about
computational vision systems: "Vision and Brain - How we
Perceive the World", he introduces his chapters with
"impressions", little prose poems about what follows.

For chapter 7, "The Color of Information", about recoding
color information in the retina and visual cortex for
processing efficiency, he provides a vignette resembling
the opening lines of a "Prisoner" episode, recoded as
an information theoretic interrogation. 

The first lines are the imprisoned secret agent, the
indented lines are an disembodied ethereal voice:

Who is number one?
     You are number six. 

What do you want?

You won't get it.
     Given that you had two alternatives, to agree or
     disagree to provide information, your negative
     response has just given us exactly one bit of
     information, thank you. 

Well, you won't be getting any more.
     Given that you had two alternatives, to tell us you
     will or you won't provide more information, your
     response gives us another bit, thank you again. 

That's a low-down, two-bit trick to play.
     We already knew that, so your response has given
     us no information. 

I'm glad to hear it.
     Given that you had two alternatives, to be glad or
     not to be glad, your response gives us another bit;
     please continue. 

I can see that the only way for me not to provide
information is to be silent.
     Fair enough. Was that your final bit? 

It was.
     Apparently not ... 

Stone's contention is that the visual system exists to
infer models of the external world, not depict or store
images.  Every step of visual processing extracts and
compacts information prior to Bayesian inference, while
minimizing metabolically expensive neuron firings.


Keith Lofstrom          keithl at keithl.com

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