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RULE 1:
There can be only one pattern per frame. Black squares singly
or in groups not attached to the pattern by at least one side or corner
are deleted. |
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RULE 2: A pattern must fit its `frame' with respect to at least one
dimension. As you can see in this example, the Dynism will have to move
closer to the `target' object to extract an Input that fits in this
way.
|
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RULE
3: Patterns must be centered. Those that are an odd number of
squares wide or high will be biased to the left or bottom of the frame
respectively. |
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RULE 4: Any white squares fully enclosed by black squares will
themselves
be converted into black squares. Such squares represent stimuli in
other
tones and will have their own patterns extracted from them.
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In
order to conform to Rules 2 and 3, the Dynism must usually be moving
either directly toward or away from a stimulus. Indeed, just as most
terrestrial
sharks must keep swimming to keep breathing, the Dynism must keep
moving
to keep seeing. To keep the stimulus centered in its retina, it
continuously
extracts `trial' patterns as it goes. A Reflex Loop can then alter the
Dynism's angle of approach according to the positions of these patterns
within their frames.
The
Dynism begins to minimize the need for `perceptual motion' by
subdividing
its retina into a much larger number of tinier cells. The Processor can
then gang-switch these into groups of four, eight, 16 or even larger
powers
of two to correspondingly double, quadruple, or otherwise increase the
size of an array. It can then extract a pattern from a stimulus at
several
distances, though some motion may be needed for an exact fit at points
in between.
To reduce the need for motion further, the retina sub-divides into much
larger numbers of tinier cells still. However, smaller cells on an
external
retina entails greater risk of damage from the environment. So let's
assume
at this point that the mantle of `Dynism' is now taken over by another
species that solves this problem by evolving an eye with a single lens
and an internal retina. Although this produces an inverted image on the
retina, matching is not affected since the Templates are simply stored
in its ROM the same way.
The
advantages of this eye are considerable. For instance,
instead of
the arrays being gang-switched across the retinal surface to capture a
stimulus, a Centering Reflex responding to a light fluctuation can move
the entire eye to place the stimulus in the center of its retina. This
allows the retinal arrays to remain stationary so that they form a set
of Chinese Boxes, one inside the other. The largest, Box 0, subtends an
arc we'll assume for the sake of illustration to be 128 degrees. Box 1
subtends an arc of 64 degrees, Box 2 32 degrees, and so on down to Box
7 which subtends an arc of just one degree. As you can see, the center
16 cells of each Box are each made up of four smaller cells from the
Box
within it acting in unison.
To
be able to fit a stimulus closely enough to eliminate the need for
motion
entirely, the photocells from which each Box is made are themselves
formed
from 32x32 arrays of subcells. These allow a Box to shrink to nearly
half
its size half a cell at a time to fit a stimulus. It only need shrink
to
this size since capturing smaller stimuli is the role of the
immediately
smaller Box, the inner colored square. To ensure a stimulus does not
extend
beyond its boundaries, it also extracts a trial 32x32 pattern derived
from
the subcells themselves, then checks that this is wholly contained
within
the outer colored square. The two colored squares therefore define a
`Limit
Zone' (yellow) within which a stimulus must fit in at least one
dimension
before the Box can extract an Input Pattern from it.
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Since the
Input Patterns the Boxes extract
represent images, not numbers,
they must be nearest-matched in Analogue fashion, not Digital. This
raises
an interesting problem. As you can see here, a visual stimulus might be
partly obscured either by a single large stimulus, or several very
small
ones. In order to reduce the chances of a mismatch, should a comparator
select the template in which the mismatched squares are distributed
evenly
over the template, or one in which they are concentrated in contiguous
bunches?
As it
happens it doesn't matter, the comparator can
just select the
first match it encounters as before. In order to explain why though,
we'll
need to look at another problem: How does the Dynism determine whether
a stimulus has been presented by the object that normally presents it
and
not some other? Responding to false stimuli not only wastes energy, it
may place the Dynism in jeopardy.
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When
an object presents a stimulus, it usually presents certain other
stimuli
adjacent to it or in the near vicinity. When the Dynism matches a
pattern
to a template with an output therefore, it must also as a `double
check'
match the patterns from at least one other such stimulus before it
copies
that output to its effectors. We'll call the mechanism that performs
this
operation an `Identifier'.
But
before we can look at how this works in any detail,
the Dynism must
first acquire a few more mechanisms.
| At
this stage in its evolution a Dynism may only be
able to match a
few of the stimuli an object might present. To illustrate, let's
imagine
one of its Prey species actually looks like this (albeit somewhat
contrived)
object. As you can see, the further away its stimuli lie from its
center,
the more distorted they become. The Dynism can therefore only match the
center ones - unless it evolves predistorted Templates for the others.
Also, several `stimuli' that we see as `complete' are bisected by the
tones
of the underlying sphere, preventing the Dynism from matching them.
Others
may be common to other objects, so that they can't be used as
`identifiers'
even when they are successfully matched. The three stimuli here may
well
be the only ones that will allow the Dynism to Identify the object as a
member of a particular Prey species. |
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In
order to capture any set of identifying stimuli quickly
enough to
identify a Predator species, the Dynism's eye must become able to
extract
patterns from several stimuli simultaneously. A Reflex Loop may evolve
to move the eye in `raster scan' fashion over its Visual Field, but
such
an eye would quickly be superseded by one that scans the Boxes across
the
retina instead, just as its external-retina predecessor did.
