Stevan Harnad (2001) Is Real Chaos Essential to Cognitive Capacity, or Will Symbolic Simulation do?. Psycoloquy: 12(051) Symbolism Connectionism (18)

Reply to Kentridge on Harnad on Symbolism-Connectionism

Department of Electronics and Computer Science

University of Southampton

Highfield, Southampton

SO17 1BJ

United Kingdom

http://www.cogsci.soton.ac.uk/~harnad/

harnad@cogsci.soton.ac.uk

Kentridge (2001) suggests that chaotic dynamics may be essential for cognition. But the performance power of chaos remains to be demonstrated, and even if it helps to pass the Turing Test, it remains to be shown (as with neural net parallelism) that serial symbolic simulation would not have done worked just as well.

REPRINT OF: Harnad, S. (1993). Harnad's response to Kentridge. Think 2: 12-78 (Special Issue on "Connectionism versus Symbolism" D.M.W. Powers & P.A. Flach, eds.). http://cwis.kub.nl/~fdl/research/ti/docs/think/2-1/index.stm

1. There are several ways to construe Kentridge's (2001) friendly suggestions about chaos and cognition; some are indeed supportive, but some may be Trojan horses! It all boils down to which of the three rooms in the three-room argument his arguments apply to: If nonlinear dynamical systems that display chaos have essential analog properties (analogous to essential parallelism, as in room one, PAR), that is, if a chaotic system is, like a transducer or a furnace, something a system has to BE in order to display certain properties essential to cognition (in other words, if just symbolically/numerically simulated chaos, 'virtual' chaos, won't do), then all we need is the demonstration that such an essential property of chaos is indeed also a property essential to cognition. Transduction had face validity, but chaos requires an argument or a proof (I'm not sure I see either in Kentridge's commentary, but perhaps I have not understood it fully).

2. On the other hand, if all the performance properties of chaos could also be exhibited by room 2 (SIM), which would now be merely a symbolic/numerical simulation of the chaotic system in room 1 (i.e., a 'nondeterministic symbolic description of the neural network's behavior,' perhaps using numerical probabilities, multiplicative interactions, even pseudo-random number generators), then we would of course be back where we were in the beginning.

3. My own approach has the virtue of not stipulating anything about the innards of the winning(Total-Turing-Test-passing) system except that it must include sensorimotor transduction, which is of necessity analog. I can't tell whether Kentridge's proposal pertains only to properties of the innards (a nonlinear dynamical system with the capacity to exhibit chaos), or also to the properties of the analog input itself (in which case our positions are even more compatible). One still waits, of course, to see the full performance capacity of chaos (whether simulated or real): Can it, for example, help us pass the TTT?.

Harnad, S. (2001) Grounding symbols in the analog world with neural nets -- A hybrid model. PSYCOLOQUY 12(034) http://www.cogsci.soton.ac.uk/cgi/psyc/newpsy?12.034

Kentridge, R.W. (2001) Cognition, chaos and non-deterministic symbolic computation: the chinese room problem solved?. PSYCOLOQUY 12(050) http://www.cogsci.soton.ac.uk/cgi/psyc/newpsy?12.050