Memory, thinking and language.pdf
Memory, thinking and language.pdf
Memory, thinking and language.pdf
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20<br />
Figure 4 Part of Collins <strong>and</strong> Quillian’s (1969) semantic hierarchy for<br />
animals.<br />
knowledge stored in human memory is like the information<br />
stored in the database of a computer. So the implication of the<br />
Collins <strong>and</strong> Quillian model is that people’s knowledge of objects<br />
in the environment is organized as a semantic hierarchy of<br />
concepts <strong>and</strong> categories. Of course, the network in Figure 4<br />
displays only a tiny fraction of all human knowledge. It is meant<br />
to reflect biological knowledge that cats <strong>and</strong> dogs <strong>and</strong> birds<br />
are animals, that pigs can’t fly, that elephants have trunks <strong>and</strong><br />
that whales are mammals. To represent the vast amount of<br />
knowledge in human memory there would have to be<br />
thous<strong>and</strong>s, perhaps millions, of other concept hierarchies, for<br />
example about man-made objects, abstract ideas, <strong>and</strong> many<br />
others. In addition there are many links between hierarchies, for<br />
example canaries are often kept in man-made cages. One reason<br />
why Quillian’s biological hierarchy was taken up by<br />
psychologists was that his model was experimentally tested by<br />
Collins <strong>and</strong> Quillian (1969) using a sentence verification task.<br />
Subjects were asked to judge (verify) whether sentences are true<br />
or false, for example Acanary is a bird, A shark is a bird, A canary<br />
can sing, A canary canbreathe. The prediction was that people<br />
would take longer to decide about sentences which involve<br />
longer searches through the network. The results of the<br />
experiment confirmed this prediction. Sentences which require a