  This paper hypothesizes that chunking plays important role in reducing
dependency distance and dependency crossings. Computer simulations, when
compared with natural languages,show that chunking reduces mean dependency
distance (MDD) of a linear sequence of nodes (constrained by continuity or
projectivity) to that of natural languages. More interestingly, chunking alone
brings about less dependency crossings as well, though having failed to reduce
them, to such rarity as found in human languages. These results suggest that
chunking may play a vital role in the minimization of dependency distance, and
a somewhat contributing role in the rarity of dependency crossing. In addition,
the results point to a possibility that the rarity of dependency crossings is
not a mere side-effect of minimization of dependency distance, but a linguistic
phenomenon with its own motivations.
