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 DJ Bryant: REPRESENTING THE ENVIRONMENT IN THE SPATIAL REPRESENTATION SYSTEM
            Reply to Montello on Bryant on Space

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psycoloquy.92.3.58.space.11.bryant          Saturday,  October 31, 1992
ISSN 1055-0143                 (9 paragraphs, 11 references, 188 lines)
PSYCOLOQUY is sponsored by the American Psychological Association (APA)
                Copyright 1992 David J. Bryant

    REPRESENTING THE ENVIRONMENT IN THE SPATIAL REPRESENTATION SYSTEM
                Reply to Montello on Bryant on Space

                David J. Bryant
                Department of Psychology, 125 NI
                Northeastern University
                Boston, MA 02115
                (617) 437-3548
                bryant@northeastern.edu

0.1  Montello (1992) offers a number of interesting comments from the
perspective of environmental cognition. In this reply, I would like to
clarify one of the assumptions of the original Spatial Representation
System (SRS) account (Bryant 1992) and to question Montello's (1992)
claim that only egocentric frames of reference are used in working
memory.

1.0  INFERRED VERSUS EXPERIENCED SPATIAL RELATIONS

1.1  Montello (1992) questions Bryant's (1992, section 3.7) claim that
people have equal access to inferred and explicitly described or
perceived spatial relations. This assumption was originally intended to
mean that when the location of an object is encoded in a particular
coordinate space, both explicit and implicit relations have equal
status. Spatial relations between objects are represented by the
relations between their locations in the coordinate space, so that
there is no difference between relations that were experienced versus
those that were not. All "inferences" are made as a consequence of
placing objects in the same frame of reference.

1.2  This is not to imply that people automatically make inferences
between different frames of reference or separate spatial models;
the studies cited by Montello (1992) demonstrate this. The study by
Hanley and Levine (1983) is especially illustrative. In their
experiments, subjects learned two different paths by touch, one with
their left hand and the other with their right. After a study period,
subjects were informed that there was a common point on each path and
that they were to integrate the two paths into a single configuration.
Then subjects were tested on their ability to move from one point to
another in the combined paths. Hanley and Levine found that the speed
and accuracy of subjects' responses were equivalent for originally
learned and inferred movements within a path they had learned. On the
other hand, subjects were slower and less accurate when attempting to
infer the relation between points from different paths. In other words,
for each path, subjects built a spatial representation in which
inferred spatial relations were just accessible as experienced
relations. When they attempted to combine two distinct spatial
representations, however, inferred relations did not have equal status
with experienced relations within the paths.

1.3  The results of Hanley and Levine (1983) imply that integrating
existing spatial models requires more complicated computations than
originally locating objects in a spatial model. What determines the
relative accuracy of inferred relations in this case is the complexity
of the computations required to translate from one spatial model or
frame of reference to another. Along this line, Rieser (1989) reported
differences in people's ability to locate objects after rotating or
moving relative to the objects. In his experiments, subjects sat in the
center of a room surrounded by objects. After observing the objects,
subjects were blindfolded and asked to point to objects to provide
baseline accuracy and response time measures. In the rotation
condition, subjects either physically rotated to face a new direction
or imagined such a rotation. In the translation condition, subjects
either physically moved to the location of one of the objects or asked
to imagine such a translation. Rieser found that subjects were less
accurate and took longer to point to objects when they had rotated or
imagined a rotation but were as fast and accurate in pointing after a
translation (providing the subject did not also rotate). Rieser
suggested that subjects encoded the object to object relations and were
able to retrieve them directly in the translation condition but that
additional processing was required to compute new object-to-self
relations after a rotation. Consistent with this idea was the finding
that the magnitude of error depended on the amount of rotation.

1.4  Thus, there is evidence (see also Bryant, Tversky, & Franklin
1992; Byrne & Johnson-Laird 1989) that people have equal access to
experienced and inferred spatial relations within a single frame of
reference. As a person locates objects with the coordinate space formed
by a reference frame, the SRS account predicts that there should be no
difference between spatial relations that are perceived or heard in a
description and those which are not. Montello (1992), however, is
certainly right that inferred spatial relations are not equivalent to
experienced relations in the larger sense when we discuss inferences
between separate spatial models or different frames of reference.

2.0  ALLOCENTRIC SPATIAL MODELS AND WORKING MEMORY

2.1  Montello (1992) equates allocentric (survey) representations with
long-term memory (LTM) and egocentric (route) representations with
working memory (WM). In this scheme, one stores a survey map of the
environment in LTM, but to use that spatial knowledge to guide behavior
in space one must convert the survey map to an egocentric route
representation in WM. Thus, Montello proposes not only that people use
two different frames of reference for representing space, but that they
are limited in which frame can be used in long- and short-term memory.

2.2  In the SRS account, the distinction between LTM and WM was not
explicitly made. The account assumes that the SRS creates mental models
based on allocentric and egocentric reference frames. Mental models
interact with WM during retrieval (Johnson-Laird 1989), so I must
assume that if people use allocentric models in LTM they can
instantiate these models in WM as well. This does not mean that people
cannot use an allocentric cognitive map in LTM to generate an
egocentric route map or to imagine a survey map. These are undoubtedly
common strategies for dealing with the task of navigating through the
environment. However, it seems an unnecessary restriction to say that
WM can only accommodate egocentric representations.

2.3  Recently, Hirtle and Mascolo (1991) examined the strategies and
heuristics people use to estimate distances. Some of the strategies
they discovered involve egocentric or route representations such as
estimating the distance between two places by calculating the time it
would take to travel from one to the other. Other strategies, however,
involved computations performed directly on an allocentric cognitive
map. These included the use of analogies (A is to B as C is to D) and
triangulation, in which two sides of a triangle are used to calculate
the hypotenuse. Hirtle and Mascolo (1991) found evidence of up to 21
distinct heuristics for calculating distance, many of which were
performed on allocentric representations. It is likely that many other
spatial tasks can likewise be performed by a number of different
strategies using egocentric or allocentric representations.

2.4  Another example in which people seem to use allocentric
representations in WM is the phenomenon of spatial priming. In a
classic study, McNamara (1986) found that when subjects learn the
layout of objects in a room, their recognition latencies for the
objects are influenced by the objects' spatial proximity in the
layout. Thus, an item facilitated recognition of another more if the
two had been close together in the environment rather than far apart.
This priming effect was based on an allocentric representation of the
layout rather than an egocentric one because priming was determined by
location in the room independent of the route or egocentric perspective
subjects used during study. Spatial priming seems to depend on having
the allocentric representation in WM because the priming effects are
not obligatory and are found only when subjects are cued to the spatial
relations at the time of the recognition test (Clayton & Chattin 1989;
McNamara, Altarriba, Bendele, Johnson, & Clayton 1989). Although
subjects must retrieve the spatial representation to generate priming,
the recognition test does not require mental imagery and there is no
evidence that subjects scanned a mental image.

REFERENCES

Bryant, D. J. (1992) A Spatial Representation System in Humans.
PSYCOLOQUY 3(16) space.1.

Bryant, D. J., Tversky, B., & Franklin, N. (1992) Internal and
External Spatial Frameworks for Representing Described Scenes.
Journal of Memory and Language 31: 74-98.

Byrne, R. M. J., & Johnson-Laird, P. N. (1989) Spatial reasoning.
Journal of Memory and Language 28: 564-575.

Clayton, K., & Chattin, D. (1989) Spatial and Semantic Priming
Effects in Tests of Spatial Knowledge. Journal of Experimental
Psychology: Learning, Memory, and Cognition 15: 495-506.

Hanley, G. L., & Levine, M. (1983) Spatial Problem Solving:  The
Integration of Independently Learned Cognitive Maps. Memory &
Cognition 11: 415-422.

Hirtle, S. C., & Mascolo, M. F. (1991) The Heuristics of Spatial
Cognition. In the Proceedings of the 13th Annual Conference of the
Cognitive Science Society (pp. 629-634). Hillsdale, NJ: Erlbaum.

Johnson-Laird, P. N. (1989) Mental Models. In M. I. Posner (Ed.),
Foundations of Cognitive Science. Cambridge, MA: MIT Press.

McNamara, T. P. (1986) Mental Representations of Spatial Relations.
Cognitive Psychology 18:87-121.

McNamara, T. P., Altarriba, J., Bendele, M., Johnson, S. C., & Clayton,
K. N. (1989). Constraints on Priming in Spatial Memory: Naturally
Learned Versus Experimentally Learned Environments. Memory &
Cognition 17: 444-453.

Montello, D. R. (1992) Characteristics of Environmental Spatial
Cognition. PSYCOLOQUY 3(52) space.10.

Rieser, J. J. (1989) Access to Knowledge of Spatial Structure at
Novel Points of Observation. Journal of Experimental Psychology:
Learning, Memory and Cognition 15: 1157-1165.