Abstract
It has been recently shown (e.g., Hornik, Stinchcombe & White, 1989, 1990) that sufficiently complex multilayer feedforward networks are capable of representing arbitrarily accurate approximations to arbitrary mappings. We show here that these approximations are learnable by proving the consistency of a class of connectionist nonparametric regression estimators for arbitrary (square integrable) regression functions. The consistency property ensures that as network “experience” accumulates (as indexed by the size of the training set), the probability of network approximation error exceeding any specified level tends to zero. A key feature of the demonstration of consistency is the proper control of the growth of network complexity as a function of network experience. We give specific growth rates for network complexity compatible with consistency. We also consider automatic and semi-automatic data-driven methods for determining network complexity in applications, based on minimization of a cross-validated average squared error measure of network performance. We recommend cross-validated average squared error as a generally applicable criterion for comparing relative performance of differing network architectures and configurations.
Published Version
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