These are excerpts and elaborations from my book "The Nature of Consciousness"
Homeostasis The US mathematician Norbert
Wiener (who founded Cybernetics in
1943) first recognized the importance of feedback (a term that he coined) for
any meaningful behavior in the environment: a system that has to act in the
environment must be able to continuously compare its performed action with the
intended action and then infer the next action
from their difference. This is
what all living organisms do all the time in order to survive. Feedback is the action of
feeding a system its past performance. Given past performance, the system can
adjust future performance. All biological systems (animals, plants, ecosystems)
exhibit feedback. Feedback is the basis of life. As Bernstein had asserted, we
could not even coordinate our limbs if we were not capable of using feedback. Feedback is crucial for
"homeostasis", the phenomenon (first described in the 1930s by the US
biologist Walter Cannon) by which an organism tends
to compensate variations in the environment in order to maintain its internal
stability; i.e., by which an organism adapts to the environment. Homeostasis
consists in maintaining a constant internal state in reaction to changes in the
environment and through action on the environment. For example, body temperature
is controlled by perspiring and shivering (one lowers the temperature and the
other one increases it). Homeostasis is crucial for survival. Given the number of factors
that must be taken into account for any type of action in the real world, it is
not surprising that the brain evolved to use feedback, rather than accurate
computation, to guide motion. It is not a coincidence that
feedback turns out to be as crucial also for the performance of machines in
their environment. Beginning with James Watt’s steam engine, machines have been
designed so as to be able to control themselves. A control system is a system
that uses feedback to achieve some kind of steady state. A thermostat is a
typical control system: it senses the temperature of the environment and
directs the heater to switch on or off; this causes a change in the
temperature, which in turn is sensed by the thermostat; and so forth. This loop
of action and feedback, of sensing and controlling, realizes a control system.
A control system is therefore capable of achieving a "goal", is
capable of "purposeful" behavior (as opposed to the chaotic behavior
that would result if feedback was not used). Living organisms are control
systems. Most machines are also control systems. Another folk concept that
Wiener formalized is “noise”. Wiener
emphasized that communication in nature is never perfect: every message carries
some involuntary "noise" and in order to understand the communication
the original message must be restored. This led to a statistical theory of
amount of information. Wiener understood the essential unity
of communication, control and statistical mechanics, which is the same whether
the system is an artificial system or a biological system. This unified discipline
became "Cybernetics". A
cybernetic system is a system that achieves an internal homeostatic control
through an exchange of information between its parts. The British neurologist Ross
Ashby also placed emphasis on
feedback. Both machines and living
beings tend to change in order to compensate variations in the environment, so
that the combined system is stable. For living beings this translates into
"adaptation" to the environment.
The "functioning" of both living beings and machines depends
on feedback processes to the extent that feedback allows the system to
self-organize. Ashby emphasized the
power of self-organizing systems, systems made of a very high number of simple
units which can evolve autonomously and adapt to the environment by virtue of
their structure. Ashby believed that in every
isolated system that is
subject to constant forces "organisms" arise that are capable of
adapting to their environment (i.e., that tend towards stationary or
quasi-stationary non-equilibrium states). Basically, his principle of
self-organization asserts that in any isolated system, life and intelligence
inevitably develop. Back to the beginning of the chapter "Machine Intelligence" | Back to the index of all chapters |