>>The model for intelligence is the human brain. The brain is the only
>>machine known that is capable of producing motor acts that we class as
>>intelligent. The notion was promulgated at the Dartmouth Summer
>>Conference that intelligence had been described by the predicate
>>calculus, and that all that was needed was to mechanize the
>>manipulative algebra; the platform being irrelevant. This was done,
>>but with unsatisfactory results.
>>We assert that any study on intelligence must be rooted in the brain.
>>It must concern itself with the chemistry and circuitry of the brain.
>>We reject Emergentism. When we explain the brain, or a computer
>>simulation of the brain, we are finished. There is no soul (mind) to
>>appear as resident in the machine.
>>The classical approach to the brain follows the Bell-Magendie law.
>>Sensory input leads to motor output. This is a passive view. I suggest
>>that we can take a more active view by emphasizing circuitry in the
>>middle, the central pattern generator (CPG). All motor output starts
>>in a CPG. Without a triggered CPG, an organism does nothing. Without a
>>triggered CPG, a human is just a lump of clay.
>>The central pattern generators are constructed by the genome. The
>>brain is a structure organized by the genome. It enters the world,
>>ready for action. Workers in Neural Nets could note this. The brain
>>does not self-organize. The genome does the organization. The brain
>>adapts itself to the universe that it encounters.
>>The rules by which the brain adapts are set up by the genome. The
>>rules are chemical. Axons grow, synapses form. Axons are retracted,
>>synapses sloughed off. Synapses are strengthened; synapses are
>>weakened. What else is needed?
Maybe we are really like this;
...Brooks's ideas gelled in a cockroachlike contraption the size of a
football called "Genghis." Brooks had pushed his downsizing to an
extreme. Genghis had six legs but no "brain" at all. All of its 12
motors and 21 sensors were distributed in a decomposable network
without a centralized controller. Yet the interaction of these 12
muscles and 21 sensors yielded an amazingly complex and lifelike
behavior.
Each of Genghis's six tiny legs worked on its own, independent of the
others. Each leg had its own ganglion of neural cells-a tiny
microprocessor-that controlled the leg's actions. Each leg thought for
itself! Walking for Genghis then became a group project with at least
six small minds at work. Other small semiminds within its body
coordinated communication between the legs. Entomologists say this is
how ants and real cockroaches cope-they have neurons in their legs
that do the leg's thinking.
In the mobot Genghis, walking emerges out of the collective behavior
of the 12 motors. Two motors at each leg lift, or not, depending on
what the other legs around them are doing. If they activate in the
right sequence-Okay, hup! One, three, six, two, five, four!-walking
"happens."
No one place in the contraption governs walking. Without a smart
central controller, control can trickle up from the bottom. Brooks
called it "bottom-up control." Bottom-up walking. Bottom-up smartness.
If you snip off one leg of a cockroach, it will shift gaits with the
other five without losing a stride. The shift is not learned; it is an
immediate self-reorganization. If you disable one leg of Genghis, the
other legs organize walking around the five that work. They find a new
gait as easily as the cockroach.
In one of his papers, Rod Brooks first laid out his instructions on
how to make a creature walk without knowing how:
There is no central controller which directs the body where to put
each foot or how high to lift a leg should there be an obstacle ahead.
Instead, each leg is granted a few simple behaviors and each
independently knows what to do under various circumstances. For
instance, two basic behaviors can be thought of as "If I'm a leg and
I'm up, put myself down, " or "If I'm a leg and I'm forward, put the
other five legs back a little." These processes exist independently,
run at all times, and fire whenever the sensory preconditions are
true. To create walking then, there just needs to be a sequencing of
lifting legs (this is the only instance where any central control is
evident). As soon as a leg is raised it automatically swings itself
forward, and also down. But the act of swinging forward triggers all
the other legs to move back a little. Since those legs happen to be
touching the ground, the body moves forward.
Once the beast can walk on a flat smooth floor without tripping, other
behaviors can be added to improve the walk. For Genghis to get up and
over a mound of phone books on the floor, it needs a pair of sensing
whiskers to send information from the floor to the first set of legs.
A signal from a whisker can suppress a motor's action. The rule might
be, "If you feel something, I'll stop; if you don't, I'll keep going."
While Genghis learns to climb over an obstacle, the foundational
walking routine is never fiddled with. This is a universal biological
principle that Brooks helped illuminate-a law of god: When something
works, don't mess with it; build on top of it. In natural systems,
improvements are "pasted" over an existing debugged system. The
original layer continues to operate without even being (or needing to
be) aware that it has another layer above it.
When friends give you directions on how to get to their house, they
don't tell you to "avoid hitting other cars" even though you must
absolutely follow this instruction. They don't need to communicate the
goals of lower operating levels because that work is done smoothly by
a well-practiced steering skill. Instead, the directions to their
house all pertain to high-level activities like navigating through a
town.
Animals learn (in evolutionary time) in a similar manner. As do
Brooks's mobots. His machines learn to move through a complicated
world by building up a hierarchy of behaviors, somewhat in this order:
Avoid contact with objects
Wander aimlessly
Explore the world
Build an internal map
Notice changes in the environment
Formulate travel plans
Anticipate and modify plans accordingly
The Wander-Aimlessly Department doesn't give a hoot about obstacles,
since the Avoidance Department takes such good care of that.
http://www.kk.org/outofcontrol/ch3-b.html
