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Questions and Summary of Hutchins (Navigation as Computation)
discussed by John Stricker
In this chapter, Hutchins' attempts to apply David Marr's approach to
understanding information processing systems to the study of navigation.
Marr's approach consists of several levels of description:
1) Computational Theory Of the Task
--What does the system do?
--Why does the system do what it does?
--What constraints are involved?
2) Implementation of the Computational Theory
--How are input and output represented?
--What is the algorithm for the transformation from input to output?
3) Hardware implementation
--How can the representation and algorithm be realized physically?
Marr's approach was designed to deal with the explanation of processes within
an individual, and the philosophy of his approach emphasized the importance of
the first stage of description. Hutchins wishes to extend this theory outside
of individuals and apply it to navigation. Additionally, Hutchins focuses upon
the 2nd and 3rd stages of description. In particular, Hutchins is interested in
the different ways in which a computational theory can be represented and
implemented.
Hutchins then presents a basic computational theory of navigation in which he
describes the basic questions of navigation as:
1) trying to determine one's position
2) trying to predict one's position at a later point in time
3) trying to determine how to end up at a specific position.
In terms of constraints for this computational theory, Hutchins describes sea
navigation as functionally occurring in two dimensions with 4 principle one
dimensional constraints:
1) Linear Positional
2) Circular Positional
3) Position-Displacement
4) Distance-Rate-Time
These one dimensional constraints can be combined to obtain navigational
solutions. For example, in trying to determine one's position, you can combine
a line of position (for example a bearing from a particular landmark) and a
circle or arc of position (knowing the distance you are from that landmark) to
obtain a position fix.
Hutchins further illustrates these constraints by describing various ways in
which they are implemented in western navigation. Of primary importance, is the
use of the navigational chart, which is described by Hutchins as a digital to
analog computer. Hutchens notes that there are many different ways within
Western navigation in which a chart can be represented. Furthermore, the chart
itself does not represent a form of reality, in fact, in order for computation,
reality can be sacrificed for function.
To illustrate further variations in representation and implementation, Hutchins
details the navigational techniques of the Micronesians. Hutchins contends that
while the Micronesians use representations which are very different from
western methods, they still operate under the same computational theory.
According to Hutchins, failure to understand this point has lead to a great
deal of confusion in trying to understand the methods used by the Micronesians.
Operating essentially by using star paths (a succession of evenly spaced stars
which appear to rise and set at the same point on the horizon) and the concept
that the canoe does not move, but rather the islands themselves move, the
Micronesians developed a system which enables them to accurately navigate in
the vicinity of the Caroline Islands. Hutchins describes how only when we stop
thinking of western representations of navigation as the best representation
are we able to understand the Micronesian system. He then describes how the
process of Micronesian navigation maps on to the computational theory of
navigation described earlier.
According to Hutchins, there are many parallels between Pre-modern western
navigation and an unsophisticated version of Micronesian navigation. However,
the divergence of the two systems can be explained mainly through the creation
of tools and the interaction of tools and representations. Unlike the
Micronesian navigator, the Western Navigator developed tools to store knowledge
and make computations easier. By developing these tools, the western
representations of navigation became more and more dependent upon these tools
as they began to represent knowledge and computations which were too immense or
difficult for mental storage and calculation. This has occurred to such an
extent that for Western navigators there has emerged, as Hutchins describes it,
"=85a passion for measuring and a penchant for taking the representation more
seriously than the thing represented."
In describing the development of representations and tools in Western
Navigation, Hutchins also illustrates how the tools themselves can dictate how
representations will further develop. In discussing the relationship between
tools, representations, and the task at hand, Hutchins states that "it is a
truism that we cannot know what the task is until we know what the tools are.
Not only is this true of both internal and external tools, it is also true of
the relationships among them."
Hutchins also contends that we often have difficulty understanding other
representations because we are too wrapped up in our own. But by studying the
history and the way in which our own representations have developed (and
thereby seeing how they may have developed in a different manner) we can begin
to understand the possible diversity in approaches to solving the problem of
navigation.
Discussion
>From this article the message seems to be that the physical and conceptual
worlds interact more often then one would think, and that either one can change
or influence the other. From this point, it is further suggested that the
environment in which cognition occurs needs to be examined more closely, and
that cognition does not exist in a vacuum. But might this lead us away from
formulating computational theory and reduce the study of cognition to the
delineation of an infinite number of representations and implementations?
Perhaps not, with the example of the Micronesians, this approach enabled
Hutchins to recognize and specify similarities and differences between
Micronesian navigation and Western navigation. But even keeping the usefulness
of this technique in mind, is it then worthwhile to focus upon the similarities
only and try to weed out the differences, trying to find the =91pure'
cognition? Perhaps it is through these comparisons that we are able to find the
computational theory of the problem.
The topic of navigation has a strong functional theme which easily lends itself
to a problem solving formulation. Yet many developments of concepts and tools
may not be so characteristically functional. Or are they? Can all of cognition
be described as problem solving? Can the way in which navigation is discussed
in this chapter also be applied to more complex human developments, such as the
development of science, religion, or philosophy?
This also hints at the issue of Hutchins applying Marr's approach to groups of
individuals in different environments...Tackling the subject of navagation is
addressing a different level of problem solving than attempting to study
vision. With vision, although there is not always a clear relationship between
levels of description physical hardware, the representation, and the
computational theory, the distinctions between the physical hardware and the
representation do not seem nearly as fuzzy. In studying navigation, it is
difficult to tell what is physical implimentation and what is representation.
Could the same be said for the study of vision?
Regarding the divergence of navigation techniques, what is it that prompts such
a reliance upon tools? Hutchins points out in his chapter that it was not
necessary for the Micronesians to develop ways to store or compute information
because they did not have a wide sailing area, but that does not seem like
enough of an explanation. Western society seems to carry out this theme
(storing knowledge in tools and then having tools dictate further advances in
concepts) in every aspect of life, not just navigation, what other cultural
aspects may contribute?
John L. Stricker
johnsjr@earthlink.net
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