Language Evolution and Computation Bibliography

Deacon has suggested that one of the key factors of language evolution is not characterized by an increase in genetic contribution, often known as the Baldwin effect, but rather by a decrease. This process effectively increases linguistic learning capability by organizing a novel synergy of multiple lower-order functions previously irrelevant to the process of language acquisition. Deacon posits that this transition is not caused by natural selection. Rather, it is due to the relaxation of natural selection. While there are some cases in which relaxation caused by some external factors indeed induces the transition, we do not know what kind of relaxation has worked in language evolution. In this article, a genetic-algorithm-based computer simulation is used to investigate how the niche-constructing aspect of linguistic behavior may trigger the degradation of genetic predisposition related to language learning. The results show that agents initially increase their genetic predisposition for language learning—the Baldwin effect. They create a highly uniform sociolinguistic environment—a linguistic niche construction. This means that later generations constantly receive very similar inputs from adult agents, and subsequently the selective pressure to retain the genetic predisposition is relaxed.

Since Hinton & Nowlan published their seminal paper (Hinton & Nowlan 1987), the neglected evolutionary process of the Baldwin effect has been widely acknowledged. Especially in the field of language evolution, the Baldwin effect (Baldwin 1896d, Simpson 1953) has been expected to salvage the long-lasting deadlocked situation of modern linguistics: i.e., it may shed light on the relationship between environment and innateness in the formation of language.

However, as intense research of this evolutionary theory goes on, certain robust difficulties have become apparent. One example is genotype-phenotype correlation. By computer simulations, both Yamauchi (1999, 2001) and Mayley (1996b) show that for the Baldwin effect to work legitimately, correlation between genotypes and phenotypes is the most essential underpinning. This is due to the fact that this type of the Baldwin effect adopts as its core mechanism Waddington's (1975) `genetic assimilation'. In this mechanism, phenocopies have to be genetically closer to the innately predisposed genotype. Unfortunately this is an overly na{umlaut}yssumption for the theory of language evolution. As a highly complex cognitive ability, the possibility that this type of genotype-phenotype correlation exists in the domain of linguistic ability is vanishingly small.

In this thesis, we develop a new type of mechanism, called `Baldwinian Niche Construction (BNC), that has a rich explanatory power and can potentially overcome this bewildering problem of the Baldwin effect. BNC is based on the theory of niche construction that has been developed by Odling-Smee et al. (2003). The incorporation of the theory into the Baldwin effect was first suggested by Deacon (1997) and briefly introduced by Godfrey-Smith (2003). However, its formulation is yet incomplete.

In the thesis, first, we review the studies of the Baldwin effect in both biology and the study of language evolution. Then the theory of BNC is more rigorously developed. Linguistic communication has an intrinsic property that is fundamentally described in the theory of niche construction. This naturally leads us to the theoretical necessity of BNC in language evolution. By creating a new linguistic niche, learning discloses a previously hidden genetic variance on which the Baldwin `canalizing' effect can take place. It requires no genetic modification in a given genepool. There is even no need that genes responsible for learning occupy the same loci as genes for the innate linguistic knowledge. These and other aspects of BNC are presented with some results from computer simulations.

Turkel [16] studies a computational model in which agents try to establish communication. It is observed that over the course of evolution, initial plasticity is significantly nativised. This result supports the idea that innate language knowledge is explained by the Baldwin effect [2][14]. A more biologically plausible computational model, however, reveals the result is unsatisfactory. Implications of this new representation system in language evolution are discussed with a consideration of the Baldwin effect.