Cognitive Processes PSY 334 Chapter 5 – Meaning-Based Knowledge Representation April 30, 2003

Demos Penny Eidetic imagery (photographic memory)

Propositional Representations Notation – a method for describing the meaning that remains once details have been abstracted away. Propositional representation – uses concepts from logic and linguistics to describe meaning. Proposition – the smallest unit of knowledge that can be judged as true or false.

Propositional Analysis A complex sentence consists of smaller units of meaning (propositions). If any of the propositions are untrue, the entire sentence cannot be true. The meaning of primitive assertions is preserved, but not the exact wording.

Kintsch’s Notation Each proposition is a list containing a relation plus arguments: (relation, arguments) Relation – organizes the arguments. Verbs, adjectives, other relational terms. Arguments – particular times, places, people, objects. Nouns Relations connect arguments.

Psychological Reality Psychological reality -- do propositions really exist mentally? Bransford & Franks: Presented 12 sentences with the same 2 sets of 4 propositions. Tested on 3 kinds of sentences. Old (previously viewed), new (containing same propositions), noncase (new and containing different propositions). Able to identify noncase, but not old/new

Propositional Networks Propositional network – another way of representing propositions (the structure of meaning). Nodes – the propositions, including relations and arguments. Links – labeled arrows connecting the nodes. Spatial location of nodes is arbitrary. Can show hierarchies of meaning.

Associations Between Ideas Weisberg – demonstrated that ideas are associated in the ways shown in a propositional network. Subjects memorized sentences. Given a word from the sentence, subjects were asked to say the first word that came to mind. Subjects cued with “slow” said “children” and almost never “bread”.