The Metaphor/Analogy group is interested in enhancing ProtoThinker's ability to interpret and generate linguistically complex utterances. ProtoThinker is already quite competent at analyzing simple propositions semantically. By first using numerous clues to determine the syntactic structure of a sentence, PT is able to convert sentences of a natural language (English) into the language of predicate logic. But what happens when the relationship between a proposition's surface content and its overall logical meaning is not straightforward? Such is the case with metaphorical and ironic utterances, in which a speaker's overall intention cannot be determined merely by adding together the logical function of the individual words. The metaphor/analogy group of the PT Project is interested in enhancing PT's ability to interpret (and generate) these indirect types of propositions. In more general terms, we are using Artificial Intelligence as a starting point in an investigation of the cognitive and aesthetic functions of metaphor.
Metaphor, in its broadest sense, might be defined as a description of one thing using the language of another thing. Speakers use such indirect linguistic devices for a variety of reasons; it would be premature to dismiss metaphors as mere linguistic frills that are somehow superfluous to a model of the human mind. Rather, discussion of metaphor and analogy leads us directly into the issues at the heart of the PT Project: What is intelligence? What is needed for personhood? Linguists (George Lakoff in particular) have argued that use of metaphor is not merely restricted to poetic language. Rather, metaphor underlies everyday speech and is one of the fundamental mechanisms whereby we adapt to new or challenging situations. Such familiarizing metaphors, in which we describe new experiences in terms of old ones (or unfamiliar ideas in terms of familiar ones) might even be a necessary condition for intelligence.
Of course, speakers and writers of a natural language make use of 'poetic' metaphors as well. Such defamiliarizing metaphors complement the function of familiarizing metaphors, by providing a means beyond the limitations of a static language. The Metaphor/Analogy group is investigating both types of metaphors using a simulation approach with ProtoThinker.