Ellipsis, Common Ground, and Dialogue Interaction
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                    Jonathan Ginzburg

It is commonly thought that ellipsis arises when, roughly, a content
that could have been expressed overtly is sufficiently salient as to
enable the conversational participants to easily access it from the
common ground.  The starting point for this talk will be a phenomenon
I dub the Turn Taking Puzzle which seems to fly somewhat in the face
of this intuition.  The data at issue here concern the resolution of
bare wh-phrases exemplified here by the wh-phrase `why'.  (1a), where
the original speaker keeps the turn, contrasts minimally with (1b),
where two distinct speakers are involved.  In (1a), `why' must pick up
on a fact that positively resolves the initial question A poses,
whereas when `why' is uttered by a new speaker the resolution is to a
fact characterizing A's initial utterance:

(1a) A: Where was your Grandmother's sister born? Why? 
     (Unambiguously: `Why was she born *there*?')
(1b) A:  Where was your Grandmother's sister born? B: Why?
     (`Why do you ask where she was born?')
(1c) A:  Where was your Grandmother's sister born? (and) Why am I 
     asking this question?

I will suggest that these data cannot be explained merely as a
consequence of the differing coherence of an utterance depending on
*who* makes the utterance: the resolution unavailable to A in (1a) is
coherent when it arises from a non-elliptical utterance, as in (1c);
indeed as far as plausibility goes, this latter resolution is no less
perhaps even more plausible than the actual resolution that occurs in
(1a) .  A possible conclusion, then, is that in conversation the
common ground (or however we wish to call the repository from which
conversationalists draw the semantic objects they utilize in
interpretation) is not always common.

Coming up with a detailed solution to the TTP involves a number of
interesting semantic and pragmatic issues which will form the focus of
my talk: the TTP provides us with a number of clues about the time
course of utterance resolution across speaker and addressee, more
jargonistically---clues as to how utterances update contexts.  The TTP
and related ellipsis phenomena taking place during utterance grounding
and clarification also suggest the need for radical modifications of
existing notions of meaning and content, for instance those deriving
from the Relational Theory of Meaning.