The Computer Metaphor

1
The Computer Metaphor

• The brain is a computer (an information
  processing device)
• The mind is a (collection of) programmes
• Our perceptions and cognitions are constructed
  out of the collective activity of these
  programmes

2
The Hard Problem

• Why does (some of) the brains activity generate
  subjective experience?
• Having explained everything physical about the
  brain, there is something still left over
  experience
• e.g. Childbirth
• See David Chalmers (1996) book, The Conscious
  Mind
• your 1st year Consciousness course notes

3
Cognitive Models

• Cognitive models fractionate the mind
• Initial questions for any cognitive model
• How many mechanisms?
• What does each mechanism do?
• How do the mechanisms work together? -
  functional architecture
• How do you find answers to these questions?

4
Inspiration

• Brain anatomy and function?
• What happens to cognition after brain damage?
• How are cognitive functions carried out by the
  brain?
• Man-made computing devices?
• How do computers represent, store and process
  information?
• Introspection?

5
Look Within?

• Generates descriptions of memory phenomena
• Memories pop into mind.
• It helps to have a cue to jog the memory.
• Sometimes they come back involuntarily
• But how?
• How does information become conscious?
• Where did it come from, where does it go?
• How is the target memory found?
• How can you be sure you have the right memory?
• How do you know the memory contents are accurate

6
It may depend upon your span of attention
7
Hi-fidelity
Low fidelity
It may depend upon the fidelity of episodic
encoding
8
Proprioception
9
Size Constancy and After Images

• After images have a constant retinal size
• After images change size if their perceived
  distance changes (Emmerts Law).
• The visual system somehow combines the constant
  retinal signal along with distance information to
  generate the apparent size of the after imge.

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A Visual and Proprioceptive Illusion

• Subjects were dark adapted for 5 minutes
• After image of hand produced by a flash gun
  positioned above subjects head
• Now in total darkness, hand is moved either
  towards or away from face
• Subject reports any change in size of afterimage,
  relative to initial size at start point.

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What do the Illusions Reveal?

• Hidden visual and proprioceptive mechanisms that
  underlie conscious perception
• The constructive nature of our perceptions
• The tip of the iceberg?

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Summary

• A host of processing mechanisms generate our
  conscious experiences
• The nature (i.e. how they work) of these
  mechanisms is hidden from us
• We dont realise the extent to which our percepts
  and thoughts are constructed