Unconfounding common ground

I propose that research on the role of common ground in language use is often insensitive to considerations of parsimony. By ignoring parsimony, our experiments might fall short of addressing common ground and instead the resulting data support a simpler theory which is subsumed within the theory of common ground. In order to address this inherent conceptual confound, this paper proposes the subsuming theory criterion for experiments on common ground and mutual knowledge. In practical terms, to demonstrate an effect of common ground the design must keep common information constant and only vary whether or not it is common. The paper demonstrates how consistent use of this necessary criterion will allow us to make stronger claims about when common ground plays a role and when it does not To illustrate how experiments can be designed to satisfy the criterion, the paper evaluates some earlier studies which do and don't satisfy it In general, the study of language use could benefit from tightening the rules of evidence, allowing us to draw stronger conclusions about central concepts such as common ground.