Despite its relatively fixed word order, English permits a
considerable amount of variation in the ordering of post-verbal
constituents. My goal is to explain why speakers choose one order
over another. Toward this end, Jennifer Arnold and I have been
investigating factors that might influence ordering. The most studied
of these are grammatical complexity ('heaviness') and information
structure ('newness'). Others that might be relevant include semantic
relatedness among constituents and the potential for attachment
ambiguities. I report on corpus studies and psycholinguistic
experiments designed to ascertain the influence of these factors in
determining postverbal constituent ordering. These studies suggest
that no one factor can account for the variation. Rather, ordering
appears to be influenced by a number of interacting constraints.
Further, I argue that past attempts to explain ordering variation in
psycholinguistic terms have focussed too heavily on the hearer. I
present evidence that the needs of the speaker in planning and
producing utterances play a central role in determining constituent
ordering.