How Important Are Mental Representations in Cognitive Theories

HOW IMPORTANT ARE MENTAL REPRESENTATIONS IN COGNITIVE THEORIES?

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.

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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

physical representations picture-like language-like

examples photographs drawings maps diagrams human-language formal systems: maths, symbolic logic computer programs

properties analogue iconic continuous non-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:

Entertainment Schema

Outings

THEATRE

SLOTS Place(inside) Production Dress code People

DEFAULT Everyman Contemporary Smart Friends

SPECIFIC

EPISODES

Bristol Little

Hippodrome black Partner

dress

A schema theory used in language is called scripts ,and was proposed by Schank and Abelson (1977) as away of explaining peoples knowledge and expectations for everyday events. Their well known Restaurant script was designed to test whether people would agree about which events occur in a restaurant. The idea being that we store scripts in memory to allow us to make sense of stories which concern typical events. They found that when scripts written by participants were compared there was general agreement about the main events in that scenario.

ACT* is very similar to schema theory as the mental representations here are also propostitional and symbolic. Since it is a computer model it can be programmed as a memory system, a language processor or a problem solver (e.g. the Towers Of Hanoi.). Schema theory focuses only on long term memory, whereas ACT* acts on working memory and two kinds of long term memory, declarative and procedural. Of the three models this is the only one to address the overall structure of what is being modelled. ACT* representation is organised similarly to schema theory, in organised packages of information but for declarative memory only and it is not a strictly organised hierarchy but a tangled one.

Procedural memory is represented as a production system i.e. the working memory and sets of production condition/ action rules. As such it is a well-specified account of all aspects of cognition. Unlike schema theory ACT* is modular and processing is strictly serial. Information retrieved from declarative memory is achieved via a spreading activation. The procedural memory has to check conditions (rules)