37with the regular ed ending, and produce errors like CAMED as the past of COME. These phenomena mirror
those observed in the early phases of acquisition of control over past tenses in young children.The generativity of the child's responses—the creation of regular past tenses of new verbs and the overregularization of the irregular verbs—has been taken as
strong evidence that the child has induced the rule
which states that the regular correspondence for the past
tense in English is to add a final ed (Berko, 1958). On
the evidence of its performance, then, the model can be
said to have acquired the rule. However, no special ruleinduction mechanism is used, and no special languageacquisition device is required. The model learns to behave in accordance with the rule, not by explicitly
noting that most words take ed in the past tense in English and storing this rule away explicitly, but simply by
building up a set of connections in a pattern associator
through a long series of simple learning experiences.
The same mechanisms of parallel distributed processing
and connection modification which are used in a number of domains serve, in this case, to produce implicit
knowledge tantamount to a linguistic rule. The model
also provides a fairly detailed account of a number of
the specific aspects of the error patterns children make
in learning the rule. In this sense, it provides a richer and
more detailed description of the acquisition process than
any that falls out naturally from the assumption that the
child is building up a repertoire of explicit but inaccessible rules.There is a lot more to be said about distributed models of learning, about their strengths and their weaknesses, than we have space for in this preliminary consideration. For now we hope mainly to have suggested that
they provide dramatically different accounts of learning
and acquisition than are offered by traditional models of
these processes. We saw in earlier sections of this chapter that performance in accordance with rules can
emerge from the interactions of simple, interconnected
units. Now we can see how the acquisition of performance that conforms to linguistic rules can emerge from
a simple, local, connection strength modulation process.We have seen what the properties of PDP models are
in informal terms, and we have seen how these properties operate to make the models do many of the kinds of
things that they do. The business of the next chapter is to
lay out these properties more formally, and to introduce
some formal tools for their description and analysis.
Before we turn to this, however, we wish to describe
some of the major sources of inspiration for the PDP
V. S. RAMACHANDRAN AND SANDRA BLAKESLEE
|1. ||In this and all other cases, there is a tendency for the
pattern of activation to be influenced by partially activated,
near neighbors, which do not quite match the probe. Thus,
in this case, there is a Jet Al, who is a Married Burglar. The
unit for Al gets slightly activated, giving Married a slight
edge over Divorced in the simulation.|
V. S. RAMACHANDRAN AND SANDRA BLAKESLEE
Vilayanur S. Ramachandran (1951–) received his medical degree from Stanley Medical
College, Chennai, India, and his Ph.D. from Trinity College at the University of Cambridge.
He is currently a professor of psychology, the neurosciences program, and the director of
the Center for Brain and Cognition at the University of California, San Diego, and an ad-
junct professor of biology at the Salk Institute for Biological Studies in La Jolla, California.
He has received numerous awards, including an honorary doctorate of science (D.Sc.)
from Connecticut College. One example of his recent scholarship is the coauthored article
“The Perception of Phantom Limbs: The D.O. Hebb Lecture” (Brain, 121, 1603–1630).
Sandra Blakeslee (1943–) earned a B.S. in political science from University of California at
Questia, a part of Gale, Cengage Learning. www.questia.com
Book title: The History of Psychology: Fundamental Questions.
Contributors: Margaret P. Munger - Editor.
Publisher: Oxford University Press.
Place of publication: New York.
Publication year: 2003.
Page number: 492.
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