Shared common ground influences information density in microblog texts

If speakers use language rationally, they should structure their messages to achieve approximately uniform information density (UID), in order to optimize transmission via a noisy channel. Previous work identified a consistent increase in linguistic information across sentences in text as a signature of the UID hypothesis. This increase was derived from a predicted increase in context, but the context itself was not quantified. We use microblog texts from Twitter, tied to a single shared event (the baseball World Series), to quantify both linguistic and non-linguistic context. By tracking changes in contextual information, we predict and identify gradual and rapid changes in information content in response to in-game events. These findings lend further support to the UID hypothesis and highlights the importance of nonlinguistic common ground for language production and processing.