In this book we will describe both the general features and some specific
examples of an information-processing view of cognitive development. In terms
of recent trends in psychological research, our work represents an attempt to
apply the theoretical and methodological approach of Allen Newell and Herbert Simon
( 1972) to the complex problems raised by empirical work in the Piagetian
tradition. The general paradigm is to formulate precise models of performance of
the organism at two different levels of development, and then to formulate a
model for the transition or developmental mechanisms.

The rationale for this deceptively straightforward approach was sketched by
Simon over a decade ago:

If we can construct an information processing system with rules of behavior that lead
it to behave like the dynamic system we are trying to describe, then this system is a
theory of the child at one stage of the development. Having described a particular stage
by a program, we would then face the task of discovering what additional information
processing mechanisms are needed to simulate developmental change -- the transition
from one stage to the next. That is, we would need to discover how the system could
modify its own structure. Thus, the theory would have two parts--a program to describe
performance at a particular stage and a learning program governing the transitions from
stage to stage [ Simon, 1962, pp. 154-155].

Looking back over a 20-year period, Brown ( 1970) lists several of the forces
that revitalized research in cognitive development in the late 1950s; among them
are (1) computer simulation of cognitive processes: "Since machine's -- hardware --
could accomplish information processing of great complexity, it was obviously
perfectly scientific and objective to attribute such processing to the human
brain. Why limit the mind to association by continguity and reinforcement when
the computer, admittedly a lesser mechanism, could do so much more? Com-
puters freed psychologists to invent mental processes as complex as they liked

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