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These are excerpts and elaborations from my book "The Nature of Consciousness"
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Dimensions of Cognition The obvious criticism
against production systems is that they don't "look like" our brain. David Marr claimed that a scientist can
choose either of three levels of analysis: the computational level (which
mathematical function the system must compute, i.e. an account of human
competence), the algorithmic level (which algorithm must be used, i.e. an
account of human performance) or the physical level (which mechanism must
implement the algorithm). Different sciences correspond to different levels:
Cognitive Science studies the mind at the computational level, Neurology
studies the mind at the physical level, Eye Medicine studies the mind at the
algorithmic level. Newell refined that vision by dividing
cognition into several levels. The
program level represents and manipulates the world in the form of symbols. The
knowledge level is built on top of the symbolic level and is the level of
rational agents: an agent is defined by a body of knowledge, and has some goals
to achieve and some actions that it can perform. An agent's behavior is
determined by the "principle of rationality": the agent performs
those actions that, on the basis of the knowledge it has, will bring it closer
to the goals. General intelligent behavior requires symbol-level systems and
knowledge-level systems. Newell then broadened his division of
cognitive levels by including physical and biological states. The whole band can be
divided into four bands: neural, cognitive, rational and social. The cognitive band can be
divided based on response times: at the memory level, the response time (the
time required to retrieve the referent of a symbol) is about 10 milliseconds;
at the decision level the response time is 100 milliseconds (the time required
to manipulate knowledge), at the compositional level it is one second (time
required to build actions), at the execution level it is 10 seconds (time
required to perform the action). At the rational band the
system appears as a goal-driven organism, capable of processing knowledge and
of exhibiting adaptive behavior. Back to the beginning of the chapter "Cognition: A General Property of Matter " | Back to the index of all chapters |
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