Figure

The proportion of objects recalled by subjects in Gentner, 1981, (Experiment 3), when presented with sentences involving either general, poorly connected specific, or well connected specific verbs.

similar findings for object concepts, which have favoured prototype or exemplar-based theories of categorisation.

SCHEMATA, FRAMES, AND SCRIPTS

A lot more can be said about human knowledge beyond the characterisation of object and relational concepts. Most of our knowledge is structured in complex ways; concepts are related to one another in ways that reflect the temporal and causal structure of the world. For instance, to represent the notion of an event (e.g., reading your exam results on the noticeboard) it is necessary to have a knowledge structure that relates the act of reading to the objects involved (e.g., you and the noticeboard). The knowledge structures that can represent this type of information have been variously called schemata, frames, and scripts (see also Chapters 7, 8, and 12).

Historical antecedents of schema theories

The most commonly used construct to account for complex knowledge organisation is the schema. A schema is a structured cluster of concepts; usually, it involves generic knowledge and may be used to represent events, sequences of events, percepts, situations, relations, and even objects. The philosopher Kant (1787/ 1963) originally proposed the idea of schemata as innate structures used to help us perceive the world. Kant was strongly nativist in his view that innate, a priori structures of the mind allow us to conceive of time, three-dimensional space, and even geometry (even though many school children might disagree).

9. KNOWLEDGE: PROPOSITIONS AND IMAGES 277 In the 1930s, the concept of a schema was championed in the work of Sir Frederick Bartlett TABLE 9.3

Part of the original War of the Ghosts story and one subject's subsequent recall of it (from Bartlett, 1932) The War of the Ghosts

One night two young men from Edulac went down the river to hunt seals, and while they were there it became foggy and calm. Then they heard war-cries, and they thought: "Maybe this is a war-party". They escaped to the shore, and hid behind a log. Now canoes came up, and they heard the noise of paddles, and saw one canoe coming up to them, There were five men in the canoe, and they said: "What do you think? We wish to take you along. We are going up the river to make war on the people."

.. .one of the young men went but the other returned home.. .[it turns out that the five men in the boat were ghosts and after accompanying them in a fight, the young man returned to his village to tell his tale] .and said: "Behold I accompanied the ghosts, and we went to fight. Many of our fellows were killed, and many of those who attacked us were killed. They said I was hit, and I did not feel sick."

He told it all and then he became quiet. When the sun rose he fell down. Something black came out of his mouth. His face became contorted.He was dead. (p.65) A subject's recall of the story (two weeks later)

There were two ghosts. They were on a river. There was a canoe on the river with five men in it. There occurred a war of ghosts.They started the war and several were wounded and some killed. One ghost was wounded but did not feel sick. He went back to the village in the canoe. The next morning he was sick and something black came out of his month, and they cried: "He is dead." (p. 76)_

at Cambridge University. Bartlett (1932) was struck by how people's understanding and remembrance of events was shaped by their expectations. He suggested that these expectations were mentally represented in a schematic fashion, and carried out experiments illustrating their effects on cognition. In one famous experiment, he gave English subjects a North American Indian folk tale to memorise and recall later at different time intervals. The folk tale had many strange attributions and a causal structure that was contrary to Western expectations. He found that subjects "reconstructed" the story rather than remembering it verbatim and that this reconstruction was consistent with a Western world-view (see Table 9.3 and Chapter 12 for recent replications of this study). Finally, in a developmental context, Piaget (1967, 1970) had also used the schema idea to understand changes in children's cognition.

Schema theories re-emerged as a dominant interest in the 1970s. These theories came in several, superficially different forms: Schank's (1972) conceptual dependency theory essentially uses schemata to represent relational concepts, and "story grammars" were proposed to underlie the comprehension of stories by Rumelhart and others (Rumelhart, 1975; Stein & Glenn, 1979; Thorndyke, 1977 and Chapter 12). Schemata containing organised sequences of stereotypical actions, called scripts, were proposed by Schank and Abelson (1977) to account for people's knowledge of everyday situations. Rumelhart and Ortony (1977; also Rumelhart, 1980) proposed a general theory of schemata and, in artificial intelligence, Marvin Minsky (1975) suggested similar structures called "frames", which he mainly implicated in visual perception (see Alba & Hasher, 1983, Thorndyke & Yekovich, 1980, for reviews).

Schank and Abelson's script theory

The concept of a schema is a very loose one in many respects. As it is an organising structure for knowledge, it tends to take on ostensibly different forms when representing different sorts of knowledge. However, schemata have certain common characteristics (see Panel 9.1). Earlier, in discussing relational concepts, we saw very simplified schemata in Schank's conceptual dependency representations. More elaborate examples occur in Schank and Abelson's (1977) script theory. Script theory attempts to capture the knowledge we use

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