First published 2 July 2012
Heterochronous Neural Baldwinism
Keith L. Downing
Neural Baldwinism concerns the Baldwin Effect in the evolution of brains and intelligence. The first phase of the Baldwin Effect (B.E.), wherein plasticity provides a selective advantage, is intuitive and commonplace in simulations of adaptive systems. However, the second (assimilation) phase often poses problems for Baldwinism in general, and this is particularly acute for biological neural networks, where a complex developmental process greatly confounds the mapping from genotype to functional phenotype: a brain whose synapses are tuned to perform particular tasks. Since a strong genotype-phenotype correlation is often viewed as a prerequisite to this second phase, the body's most plastic organ would appear to defy Baldwinism. However, a detailed examination of 3 key processes of neural adaptation blurs the distinction between classic developmental and learning stages of brain maturation, thus supporting a re-interpretation of Neural Baldwinism's phase II as a heterochronous shift of the bulk of these three adaptive processes from postnatal to prenatal stages. This article illustrates Heterochronous Neural Baldwinism (HNB) with artificial neural networks that evolve, develop and learn, and in which some degree of synaptic tuning shifts to the prenatal stage.