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<Paper uid="P97-1054">
  <Title>Co-evolution of Language and of the Language Acquisition Device</Title>
  <Section position="7" start_page="425" end_page="426" type="concl">
    <SectionTitle>
5 Conclusions
</SectionTitle>
    <Paragraph position="0"> Partially ordering the updating of parameters can result in (experimentally) effective learners with a more complex parameter system than that studied previously. Experimental comparison of the default (SVO) learner and the unset learner suggests that the default learner is more efficient on typologically more common constituent orders. Evolutionary simulation predicts that a learner with default parameters is likely to emerge, though this is dependent both on the type of language spoken and the presence of memory limitations during learning and parsing. Moreover, a SVO bioprogram learner is only likely to evolve if the environment contains a dominant SVO language.</Paragraph>
    <Paragraph position="1"> The evolution of a bioprogram learner is a manifestation of the Baldwin Effect (Baldwin, 1896) genetic assimilation of aspects of the linguistic environment during the period of evolutionary adaptation of the language learning procedure. In the case of grammar learning this is a co-evolutionary process in which languages (and their associated grammars) are also undergoing selection. The WML account of parsing complexity predicts that a right-branching SVO language would be a near optimal selection at a stage in grammatical development when complex rules of reordering such as extraposition, scrambling or mixed order strategies such as vl and v2 had not evolved. Briscoe (1997a) reports further experiments which demonstrate language selection in the model.</Paragraph>
    <Paragraph position="2"> Though, simulation can expose likely evolutionary pathways under varying conditions, these might have been blocked by accidental factors, such as genetic drift or bottlenecks, causing premature fixation of alleles in the genotype (roughly corresponding to certain p-setting values). The value of the simulation is to, firstly, show that a bioprogram learner could have emerged via adaptation, and secondly, to clarify experimentally the precise conditions required for its emergence. Since in many cases these conditions will include the presence of constraints (working memory limitations, expressivity, the learning algorithm etc.) which will remain causally manifest, further testing of any conclusions drawn must concentrate on demonstrating the ac- null curacy of the assumptions made about such constraints. Briscoe (1997b) evaluates the psychological plausibility of the account of parsing and working memory.</Paragraph>
  </Section>
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