Fragmentation and Information Access
Is there an English word that ends in ‘MT’? (If you are stumped, think about it for a moment and then read the last word of this abstract.) Before you figured out (or read) the answer to that question, did you possess the information that the word that is the answer is an English word that ends in ‘MT’? In a sense, yes: the word was in your vocabulary. But in another sense, no: perhaps you weren’t able to immediately answer the puzzle question. For finite agents, this phenomenon is unavoidable. We often possess a piece of information for some purposes (or with respect to some elicitation conditions) but not for other purposes (or conditions). This suggests that a mental state be represented not by a single batch of information, but rather by an ‘access table’—a function from purposes to batches of information. This representation makes clear what happens during certain ‘aha!’ moments in reasoning. It also allows us to model agents who exhibit imperfect recall, confusion, and mental fragmentation. And it sheds light on the difference between propositional knowledge and knowledge-how. The upshot is that representing mental states using access tables is more fruitful than one might have dreamt.