THE EVOLUTION OF SYNTACTIC CAPACITY FROM NAVIGATIONAL ABILITY

MARK BARTLETT, DIMITAR KAZAKOV
2006 The Evolution of Language  
Syntax And Navigation Many recent computational models (most notably those of Kirby (2002) ) have shown how syntax may naturally emerge in language in order to exploit structural properties of a semantic space. However, while such models can explain why early human protolanguages may have gained in structural complexity to become full languages, they do not explain how the ability of individuals to handle compositionality of linguistic fragments evolved: while existing models explain the
more » ... ce of syntax in language, this is predicated on an existing syntax handling capability. We present one possible explanation for the evolution of this neurological under-pinning of syntax, and outline results from a computational model which has been developed to assess its feasibility. We believe a link exists between motor and verbal sequence processing that may hold the key to the origins of syntax. We have previously discussed a model of navigation which demonstrates this link (Kazakov & Bartlett 2004) , using landmarks as beacons and describing the path between two points by the list of landmarks one has to pass by on a journey from one position to another. One can devise a impoverished formalisation which represents such a map as a regular grammar, in which landmarks correspond to terminals, crossroads to non-terminals, and rules describe paths between two positions, e.g. the rule Y → X l 1 l 2 l 3 states that to reach Y it is sufficient to be at X and then to pass by the three landmarks listed in order. With this representation, planning or following a path is equivalent to generating or parsing, respectively, a sentence of a regular language (RL). Should the navigational needs of individuals necessitate return along the same path as the outward journey, the navigational task requires a more complex formulation equivalent to a context-free language (CFL). The equivalence between the processor needed to understand these routes and a RL or CFL parser is important: if a parser was needed for navigation, it may have first evolved for this purpose. Once this parser was developed, only a relatively small change in the neural connections may have been required to make this parser available to the human brain speech circuitry. This theory draws support from existing neurological research. Ullman (2004) pinpoints several memory circuits in the brain, the procedural memory, which
doi:10.1142/9789812774262_0051 fatcat:uq2ida62ozcydjnhhmqldn6w64