Speech acts are “the basic or minimal units of linguistic communication” (John Searle). They connect two aspects of language: its ability to refer to entities and state of affairs, and its use in communication. This includes informing others about state of affairs, but also asking questions, giving commands, making promises, expressing attitudes, and even enacting changes of the world. In linguistics, successful formal theories have been developed to address the referential aspects of language – how speakers can identify the virtu-ally unlimited possible state of affairs with limited linguistic means. But speech acts proved much more difficult to model with the same level of formal explicitness.
The SPAGAD project addressed this task within the theoretical concept of dynamic interpretation, according to which the participants in a conversation enrich their shared in-formation, the Common Ground. SPAGAD developed a model of shared information with the novel notion of Commitment Spaces, which contains the information accrued at a particular point in conversation, but also the proposed future developments. This forward-looking perspective is crucial for the modelling of questions, commands and promises. Furthermore, this model does not only contain the shared factual information, but also the social commitments by the participants – e.g. information about who vouches for the truth of which proposition, and who has which attitude towards an entity or proposition.
SPAGAD undertook research in the way how aspects of speech acts are expressed in grammar, by particular words, and by prosody. For example, adverbs like "presumably" and "truly" have a particular effect on assertions; questions like "Is it not raining?" and "Isn’t it raining?" express different pre-assumptions of the speaker. SPAGAD investigated how speech acts work in discourse: How are speech acts combined, what does the selection of one act over another tell us about the communicative goals of the interlocutors? SPAGAD also analyzed the role of speech acts in communication, in particular the social norms, like truthfulness, that come with the enactment of speech acts and that are crucial for communication. SPAGAD carried out experimental and corpus-linguistic research, with an aim at precise formal modelling.
SPAGAD also led to a better understanding of the function of language in society. It was based on the assumption that when communicating, we undertake commitments to each other, and become responsible for our actions. For example, in assertions, addressees can count on that we have evidence for what we say, in questions, that we are interested in the answer, and in declarations, that we want to install certain rules in the world. This notion of commitment is central to how SPAGAD viewed speech acts.
