Here the rats are representing the maze as comprising

route to the longest. Here the rats are representing the maze as comprising
different intersecting routes to a single point and are actively comparing
those routes to each other. They have an integrated representation over
time of at least the local environment of the maze.
As I mentioned earlier in the chapter, there are two importantly different
systems of spatial relations. There is a static and unchanging system
of spatial relations holding between places and a highly changing system
of spatial relations holding between things that are always located at a
particular place but not always at the same place. Possessing an integrated
representation of space involves grasping how these two systems of spatial
relations map onto each other and being able to bring them into harmony
for navigational purposes. Part of what makes this integrated representation
so central is that all creatures capable of representing space are
themselves moving through space. This gives a second condition upon
possession of an integrated representation of the environment, namely
that any creature who can plausibly be ascribed such a representation
must be capable of reacting to the spatial properties of the objects and
stimuli it encounters in a way that is sensitive to its own changing
position.
The importance of this latter condition has been stressed by Christopher
Peacocke in the notion of perspectival sensitivity that he develops in
Sense and Content. Let me begin by explaining how Peacocke understands
the notion. Peacocke illustrates what he means with the following
example. In figure 8.1 we are to suppose that a creature at place A can
perceive an object at place B and is accustomed to obtain food at place
C. According to Peacocke, a subject who satisfies the requirement of perspectival
sensitivity, after he has moved from A to B by a path that he
recognizes as taking him from A to B, will move directly along the line
Navigation and Spatial Reasoning 213
A creature that displays perspectival sensitivity will take the shortest path to
obtain food at point C. This entails that if the creature sees food at C while at
A and later moves to B, to go to C, it will follow the path BC.
BC, rather than by moving from B along a path parallel to AC, when he
desires the food that he ordinarily obtains at C. Note, moreover, that this
requirement of perspectival sensitivity is richer than the requirement mentioned
earlier that spatial responses not be reducible to particular sequences
of movements. Although it is true that any subject for whom the
route fromAtoCis coded in terms of themovements required to get fromA
to C will fail to display perspectival sensitivity, the converse does not hold.
Accepting Peacocke’s illustration of perspectival sensitivity does not
mean, however, that we should accept without qualification his positive
account of what is going on when perspectival sensitivity is displayed.
The account he gives seems, in one important respect, to be too impoverished.
Let me explain. Peacocke’s account of perspectival sensitivity is
based upon the notion of an intentional web. Consider figure 8.2. In the
figure Ph, Pl , and Pm represent experience types in which given objects
are perceptually presented, and the arrows represent the distances and
directions in which a subject would have to move were he to decide to
move toward those objects. This diagram is what Peacocke terms an intentional
web. It is important to realize that the experience types Ph, Pl ,
and Pm are individuated in terms of what Peacocke terms sensational
properties, that is, the nonrepresentational properties that an experience
B
A
IIh¢
IIh
IIl
C IIm
IIl¢
IIm¢
214 Chapter 8
Figure 8.2
An intentional web initially centered on place A and then recentered on place B.
A subject who wants to move from A to C but finds himself having to move from
A to B before implementing his intention will follow the route given by Pl9 if he
displays perspectival sensitivity. (From Peacocke 1983, 68. Redrawn by permission
of Oxford University Press.)
has in virtue of what it is like to have that experience (Peacocke 1983, 5).
This provides the material for understanding his notion of perspectival
sensitivity, as follows:
A simplified general statement of the requirement of perspectival sensitivity would
be this: if the subject moves from one place to another, his intentional web must
be recentered on the place determined in normal circumstances by the change in
the sensational properties of his experience. . . . Perspectival sensitivity is literally
a matter, in actual and counterfactual circumstances, of the sensitivity of the subject’s
intentional actions to variations in his perspective on the world. (Peacocke
1983, 69)
The sense in which this account of perspectival sensitivity is too impoverished
seems to me to lie in its restriction of the notion of an intentional
web to occurrently perceived objects and routes to those objects. This
neglects the importance of spatial memory. A subject’s intentional web
must also include remembered locations and the routes to those locations.
This is so for the following reason. A perspectivally sensitive subject will
be sensitive to how the spatial properties of objects are altered as a function
of his changing position. Among these spatial properties will be the
spatial relations in which occurrently perceived objects stand to objects
that have been encountered in the past and will be encountered in the
future. If these spatial relations are left out of the equation, then the practical
significance of perspectival sensitivity will be severely diminished. I
propose, therefore, to take over Peacocke’s notion of perspectival sensitivity,
subject to this expansion of the core notion of an intentional web.
Three examples will show how this notion of perspectival sensitivity
can be practically deployed in operational terms. Consider the following
experiment carried out by Chapuis and Varlet (1987). The experiment
was performed outdoors with Alsatian dogs. The dogs were taken on a
leash along the path ADB shown in the diagram and shown, but not allowed
to eat, pieces of meat at A and B (see figure 8.3). The three points
were all far enough apart to be invisible from each other.3 On the assumption
that the dogs, when released, would want to obtain food from both
A and B it is clear what perspectival sensitivity would demand in this
situation, namely, that if the dogs go first to A, they then proceed directly
to B along the dotted line AB, and vice versa. And this is in fact what
occurred in 96 percent of the trials.