turing equivalence

[John Collins]

Proving that a particular connectionist architecture is turing
equivalent may convince some skeptics that we are not completely
wasting our time, but in fact it shouldn't.  A computer built of
tinker-toys might be turing equivalent, but that implies neither that
it is an interesting model of cognition, nor that it is capable of
generating any useful results IN A REASONABLE AMOUNT OF TIME. 

For some 30+ years AI researchers have had at their disposal universal
computers which are for all purposes turing equivalent.  So why has AI
failed to achieve its lofty goals?  Clearly turing equivalence is no
guarantee of success in modeling cognition.  

The term "equivalent" is misleading. How can my PC be "equivalent" to
a Cray, and yet be so much slower?  A large part of cognition involves
interacting with the real world in real time; turing equivalence tells
us nothing about the speed, efficiency, or appropriateness of
computations given our noisy and uncertain world.

I am convinced that neural nets ARE turing equivalent; but dispite
this, I remain optimistic that connectionism will inevitably succeed
where GOFAI has failed. ;-)

  John Collins
  jcollins at cs.uiuc.edu