How the world around us is represented mentally is the corner stone of cognitive architectures. It facilitates understanding of information received and perceived from our environment. The storage and retrieval of knowledge would be impossible without mental representations.
Mental representations are the way in which we create copies' of the real things around us, which we perceive. A description of a representation is a symbol, sign, image or a depiction that takes the place of a real object in the real world. .
Representations were broadly categorised into three. The analogue representation' the propositional representation' and procedural rules'. Analogue representations are those which have an image-like copy quality to them, whereas the propositional representation are based on language-like constructs. Since the arrival of connectionism another representation has been proposed that of sub-symbolic representation. Here mental representations, according to Eysenk and Keane (2002) are "distributed" patterns of activation in a connectivist network. Historically, mental representations have been interpreted by analogy with physical representations, i.e. descriptions and classifications devised for physical representations have been applied to mental representations (Paivio, 1986). Physical representations can be picture-like or language-like (see Table). Physical and mental representations
examplesphotographs drawings maps diagramshuman-language formal systems: maths, symbolic logic computer programs propertiesanalogue iconic continuousnon-analogue non-iconic digital/discrete Table: Types of physical representations (after Paivio, 1986)
The representations need then to be categorised for storage in long -term memory. These packages' of knowledge are classed as being either procedural knowledge or declarative knowledge. Procedural knowledge is knowing how to do something or precisely what to do. It is sets of rules or procedures and skills like playing the piano. Declarative knowledge is about facts.
Representations allow cognitive models to work as they are the substance' the models work on. The models for discussion share common features but are equally differentiated from each other at some level. Before looking at each of the theories mental representations it would be helpful to take a snapshot of the model structures and approaches to learning and processing to gain a fuller understanding of their strengths and weaknesses. The models compared here are Schema theory (Rummelhart and Norman 1983) ACT* Anderson) and PDP. Schema theory is said to offers a unified theory of cognition as it umbrellas all areas of cognition. It is interactive and works on stored knowledge or long-term memory. It does not address any wider structural issues. Schema is about how our learning is influenced by our previous knowledge. Brewer and Treyens (1981) set up an experiment to show that a persons memory for a scene was influenced by the schema for that scene. They correctly predicted that participants would recall more of the expected items from the room and less of the unexpected items. However a skull which was of low expectancy for the schema was recalled suggesting that recall is not completely schema driven. The mental representations used by schema theory are propostitional and symbolic. All information arriving to be processed is interpreted with respect to knowledge in long-term memory and treated accordingly. It is then assigned slots in an existing schema or a new one is created. Schemas consist of hierarchical organised packages of information with various relationships, variables, slots with values or default settings. Contained within these slots are concepts or sub-schemata. This makes a flexible system.
An example of which is a theatre schema:...