[From Clem McGowan (960417 . 2045 EDT)]
refer to Lars Christian Smith (960407 15:40 CET)
"No, it is not a trick question, I would like to know why one can't tickle
oneself. Why can't people produce this particular perception? Is there a
HPCT explanation? Or an explanation not incompatible with HPCT? Is the
concept of surprise essential to the explanation?"
Rick Marken (960411.0820), (960415.1130) and Bill Powers proposed PCT-based
explanations.
Here is (a report on) a strongly related control theory explanation -- with
an important addition -- that appeared in the April 6-12, 1996 issue of the
"The Economist" This explanation uses, in effect, a hierarchical control
model PLUS "efference" copies. As such it seems to be a model-based
control theory explanation along the lines of Hans Blom. Here are excerpts
quoted from pages 88-89 of "The Economist" :
"Why can you not tickle yourself? And what does that have to do with
artificial consciousness? Quite a lot, according to Rodney Cotterill, a
physicist at the Danish Technical University in Lyngby. After years of
pondering the workings of the brain, Dr Cotterill believes he has found the
quintessence of consciousness.
........
Consider what happens when you reach for a glass. Signals to the brain
from the eyes and fingers (called afference in the biological jargon) keep
it informed about how the task is progressing. Signals from the brain to
the fingers and eyes (called efference) make the necessary adjustments to
avoid an accident. But at the same time another type of signal, called an
efference copy, is sent out to other parts of the brain. In simple terms,
the efference copy warns the brain's sensory-receptor areas about what the
muscles are about to do. Hence, since it is anticipated, self-tickling is
not very stimulating.
Certain nerve cells in the brain are activated only if they receive
efference copy and related afference within about two-tenths of a second of
each other. This seems to be a way of discriminating between events that
the brain has caused in the environment and those over which it has no
control, and thus distinguishing self and non-self, a central aspect of
consciousness.
It is the efference copy that Dr Cotterill believes is the crucial
ingredient of consciousness. Without it, all there is is a
computer-controlled robot. With it, the computer-robot becomes aware that
it is in control of itself.
Efference copy can be produced by a brain even when no muscles move.
According to Dr Cotterill, thought itself may be efference copy looping
round and round in a way that allows a brain to simulate vision, speech and
other faculties without actually moving a muscle. Such simulations can
lead to new associations of muscular movements -- associations which are
more commonly known as ideas.
Dr Cotterill's arguments, which have just been published in the 'Journal of
Consciousness Studies,' are unlikely to be endorsed universally." (end
quote)
Speaking of robots, has there been any discussion in CSG of Rodney Brooks'
robots built using a "subsumption hierarchy" that IS a hierarchy of control
system?
---Clem McGowan