Preliminary work for vocal
and haptic navigation software for blind sailors
Mathieu Simonnet1, Jean-Yves Guinard2
and Jacques Tisseau3
1,2,3
1mathieu.simonnet@univ-brest.fr@, 2jean-yves.guinard@univ-brest.fr, 3tisseau@enib.fr
1www.pageperso.univ-brest.fr/~simonnet/anglais.htm, 3 www. cerv.fr/~tisseau.
ABSTRACT
This study
aims at the conception of haptic and vocal navigation software that permits
blind sailors to create and simulate ship itineraries. This question implies a
problematic about the haptic strategies used by blind people in order to build
their space representation when using maps. According to current theories,
people without vision are able to construct cognitive maps of their environment
but the lack of sight tends to lead them to build egocentric and sequential
mental pictures of space. Nevertheless, exocentric and
unified representations are more efficient (Piaget et al, 1948). Can blind people be helped
to construct more effective spatial pictures? Some
previous works have shown that strategies are the most important factors in
spatial performance in large-scale space (Tellevik, 1992) (Hill et al, 1993) (Thinus-Blanc
et al, 1997). In
order to encode space in an efficient way, we made our subject use the cardinal
points reference in small-scale space. During our case study, a compass
establishes a frame of external cues. In this respect, we support the
assumption that training based on systematic exocentric reference helps blind
subjects to build unified space. At the same time, this training has led the
blind sailor to change his haptic strategies in order to explore tactile maps
and perform better. This seems to modify his processing of space
representation. Eventually, we would like to study the transfer
between map representation and environment mobility. Our final point is about
using strategy based on cardinal points and haptic virtual reality technologies
in order to help the blind improve their spatial cognition.
Keywords: non-visual
spatial representation, haptic exploration strategy, virtual geographic map,
blind sailors.
1. INTRODUCTION
This paper
describes how we are taking into account blind people’s spatial cognition in
order to conceive simulation software for blind people’s navigation on a
virtual sea.
Different
spatial theories accord various spatial capacities to blind people (Fletcher,
1980). However, we know that “the main characteristic of spatial
representations is that they involve the use of reference (p.11)” (Millar, 1994).
The lack of sight tends to lead to a body centered spatial frame, but maps are
external reference frames (O’Keefe et al, 1978). How can we make exocentric
reference easier for blind people when they encode space?
“Search
strategies in haptic exploration are related to encoding processes (p.223)” (Tellevik, 1992). Therefore, it means that teaching blind people exocentric
representation should help them to use haptic exploration strategies more
effectively. Exocentric strategies aim at locating object to object regardless
of the person’s body position. This top-down reasoning appeals to cognitive
level in the first place and sensory-motor level in the second place.
The north is
the prior knowledge acquired by map-readers (Lloyd, 2000)) so we taught blind
people that the concept of cardinal points is an absolute exocentric reference.
Thus, we made them practise reasoning about the cardinal concept in order to
build exocentric spatial representations. According to Vygotsky’s
socio-cultural theory (1896-1934), psychological instruments like writing and
maps are able to reorganize individual cognition. The compass is one of them.
After testing our spatial reference task, we have experimented systematical
training with a compass. The analysis of these results focuses on the haptic
exploration strategies.
In the future,
we shall consider the essential question of the interest of cardinal strategy
for transferring spatial capacities between maps and environment. Our position
is that virtual reality can help blind people to connect micro and macro scales
in the same exocentric reference frame.
2. NON VISUAL SPATIAL THEORIES
After a survey
of debates about non-visual representation during the last century, we are
going to emphasize the distinction between egocentric and exocentric reference
frames related to the lack of vision.
2.1 History
How do blind
people build efficient space representations? During the previous century
different theories tried to answer this question and many controversies
appeared about the role of previous visual experience.
According to
the inefficiency theory (Revesz,
1933), blind people are able to build unified space representations only from
simple forms or elements. The results of a wooden blocks recognizing task show
that “touch alone is not as efficient in the perception of (…) complex tactual
form relationships as touch aided by visual images (p.13)” (Worchel, 1951). The results of a
second experiment about direction estimations in a triangle completion task
leads to conclude that kinesthetic cues were better able to perform when
translated into visual images (Worchel,
1951).
The difference
and inefficiency theories disagree. Fletcher assumes that previous results come
from a testing artifact (5). Other experiments show no difference
between blindfolded and congenitally blind adults when they were dealing with
material that was not “optically familiar” (Juurmaa, 1965). Eventually, “lack of
vision slows down ontogenic spatial development…but does not prohibit it” (Kitchin et al, 1997).
To conclude,
we have to remember that during a spatial inference task, congenitally blind
people performed as well as blindfolded (Rieser
et al, 1986).
So, the congenitally blind persons are able to construct spatial cognitive maps
but this capacity develops more slowly. The question is how the lack of vision
slows down the construction of exocentric representation.
2.2 From egocentric to exocentric reference
“Exceptions notwithstanding, there is general
understanding that in an egocentric reference frame, locations are represented
with respect to the particular perspective of a perceiver, whereas an
allocentric reference frame locates points within a framework external to the
holder of the representation and independent of his or her position (Klatzky et
al, 1998)”.
Vision is the first perceptive modality of data
concerning spatial environment (Hatwell, 2004). It gives simultaneously
varied information about objects and their configuration in distant space. In
addition to visual modality, haptic or tactile-kinesthetic modality informs
well about spatial layout (Hatwell et al, 2000). The sequential
characteristic of haptic modality leads blind people to encode an environment
in successive reference to their own body before executing spatial inference
between external objects. Nevertheless, vision is neither
necessary nor sufficient for spatial coding (Millar, 1994).
According to the Piagetian theory (Piaget et al,
1948), during their development children construct external reference frames
from egocentric reference in coordinating vision and tactile perception. When
using haptic modality, blind people have to remember the different segments of
the object as a whole in short-term memory. This cognitive effort allows them
to construct unified exocentric representation of space (Avraamides et al, 2004). In this respect, a recent experiment shows that “allocentric (exocentric)
relations can be accurately reported in all modalities […]” (Carreiras et al, 1992). Thus, spatial representation is not limited to any
particular sensory modality although processing is probably faster with vision.
To conclude, not all blind people really build an
external frame of reference but they are able to do it. Differences in coding
strategies are more implicated than their capacities of spatial perception (Millar,
1994).
3. HAPTIC EXPLORATION STRATEGIES
Since the 1990’s, researchers have correlated
exploration patterns with the nature of non-visual spatial representation.
Evidence of exocentric reference superiority leads us to use semantic
representation in order to help blind people to improve encoding processes. We
will present our hypothesis about the role of the compass on spatial
representation.
3.1 The
Known strategies
Tellevik first tested three patterns of non-visual
exploration. In this task, blindfolded subjects had to find objects in a
large-scale environment (Tellevik,
1992). Using “perimeter” patterns, subjects explored the boundaries of given
area. In “gridline” patterns, the subjects investigated internal elements of
the area to learn their spatial relationship. With using “reference-point”
patterns, subjects relate their exploration to salient elements. The results
show that search strategy in haptic exploration may be differentially related
to encoding processes. With “perimeter” and “gridline” patterns it was more
difficult for the blind to change their perspective than with “reference-point”
strategies. This shows that the latter
pattern is more exocentric than the others. So, we think “gridline” patterns do
not really give information about the relation between elements. Consequently,
“gridline” pattern is an egocentric strategy.
One year later, Hill emphasized a lack in literature
about object-to-object relationships (Hill et al, 1993). In a direction
estimation task about explored environment the results showed that “perimeter”
pattern is a “self-to-object” strategy. Furthermore, an “object-to-object”
pattern is identified and linked to distance between object reasoning.
Eventually an efficient chronology of these patterns seems to involve
“perimeter” and “object-to-object” strategies.
In this respect, Thinus-Blanc (1997) studied the
correlation between exploration patterns and spatial performance in locomotion
and handling space. Subjects without vision have to detect the changes in a
previously explored spatial layout. The same two types of patterns of
explorations are found in small and large-scale space. On the one hand, “cyclic
patterns consist in visiting a sequence of objects, with the same one beginning
and ending the cycle (p.36)”. On the other, “the back-and-forth pattern is
characterized by repeated trajectories between two places (p.36)” (Thinus-Blanc
et al, 1997). In accordance with the O’Keefe and Nadel theory, similarity
between the first type of strategy and route knowledge and the second type and
map knowledge let us emphasize that “cyclic” pattern is an egocentric reference
frame and “back-and-forth” pattern is an exocentric frame of reference (O'Keefe
et al, 1978). Here the results verify the superiority of exocentric reference
frame.
To summarize research, Ungar (2000) carried out a
literature survey of cognitive mapping without visual experience. A synthesis
of non-visual exploration patterns identifies seven distinct exploration
strategies or patterns: home base-to-object, perimeter, grid, cyclic,
perimeter-to-object, back-and-forth and object-to-object strategies which are summarized in table 1.
Recently, a doctorate thesis about “perception and
cognition of space by individuals who are blind or have low vision” introduced
a new strategy called “perimeter-to-center” (Schinazi, 2005). The subjects explored a constructed maze, located and remembered the
positions of six different salient points. The results emphasize two egocentric strategies:
“grid” and “perimeter-to-center”. The first strategy consists in exploring the
boundaries to identify the shape, size and key features of the area around the
perimeter and then the inside of it. We have added this egocentric strategy in
table 1.
Table 1: Ungar (2000) modified table:
Nature of strategies identified in the studies by Hill, et al. (1993),
Thinus-Blanc (1997) and Schinazi (2005)
Strategy |
Description |
Nature |
Home base-to-object (Hill et al, 1993) |
Moving
repeatedly between the home base (origin point for exploration) and all the
others in turn |
Egocentric |
Perimeter (Hill
et al, 1993) |
Explored the
boundaries of an area to identify the area's shape, size and key features
around its perimeter, by walking along the edge of the layout |
Egocentric |
Grid (Hill et al, 1993) |
Investigated
the internal elements of an area to learn their spatial relationships, by
taking straight-line paths from one side of the layout to the other. |
Egocentric |
Cyclic (Thinus-Blanc,
1997) |
Each
of the four objects visited in turn, and then returning to the first object |
Egocentric |
Perimeter to center (Schinazi, 2005) |
explored
the boundaries to identify the area’s shape, size and key features around the
perimeter and then inside of it |
Egocentric |
Perimeter to object (Hill
et al, 1993) |
Moving
repeatedly between an object and the perimeter |
Exocentric |
Back-and-forth
(Thinus-Blanc, 1997)) |
Moving
repeatedly between two objects |
Exocentric |
Object to object (Hill et al, 1993) |
Moving
repeatedly from one object to another, or feeling the relationship between
objects using hand or cane. |
Exocentric |
All these strategies come from movement observations. The results show that blind
people performed better when they used exocentric patterns. This evidence proves the positive correlation between a higher cognitive
spatial level and exocentric strategies.
3.1 The cardinal
strategy: a top-down process
A coherent
relationship between mental representation and sensorial information provides a
semantic encoding. Thus, the exocentric or egocentric nature of previous
spatial strategies results from cognitive processes. The top-down process, from
the map concept to environment stimuli and the bottom-up process tightly fit
into each other.
Subjects
without vision have the same stimuli at their disposal. As they do not
similarly perform, they probably do not use the same mental space concept. How
can we induce blind people to use maps as representations?
Cognitive
mapping processing requires external cues in long-term memory. We know that
“the fact that the information which is reliably available in long-term prior
experience influences modes of coding explains coding in blind conditions
(p.153)” (Millar, 1994). As we have already seen, the cognition of the north is
one of the key prerequisite in order to read a map.
Why not teach
blind people cardinal points concept?
Acredolo et
al. (1975) explain, “information related to the immediate goal of an action is
remembered more effectively than is information that is not (p.221)” (Tellevik,
1992). In this respect, we ask our blind subject to remember spatial layout
using cardinal points reference. This learning requires the use of a tactile
compass in order to provide salient external cues. We conducted an exploratory
experimentation in order to evaluate the efficiency of cardinal reference in
space encoding.
4. EXPERIMENT
As we have already seen egocentric and exocentric
spatial representations exist. This experiment attempts to observe if the
compass leads to the use of haptic exocentric patterns of exploration. At the
moment the subject of our exploratory experimentation is an adventitiously
blind individual. The man who is forty-five years old, lost his sight at
twenty-two. He agreed to be the first to test the following protocol.
4.1 ReferenceTask
The spatial
task consists in reproducing a small-scale spatial layout in an absolute
reference after changing position around a table.
4.1.1 Situation. Three square metal sheets
are placed at three different points, 90° rotated around the table. The sheets are twenty-five centimetres wide.
We use six magnetic pieces of various geometric shapes such as a
triangle, a cross, a trapezium, a disk, a half-disk and a square. Each piece is
covered with different textures: soft, rough, wire netting, cardboard, tactile
lines and crossed tactile lines. All this aims at helping the subject to
distinguish all these different objects from each other. The pieces are placed
only on the first sheet; on the other two they are placed next to them. A
non-tactile gridline is drawn on this handling space. Each magnetic piece is
placed in the middle of a five centimetre non-tactile square. The grid lines
allow us to measure errors when the blind subject reproduces the layout (cf.
figure 1).
Figure
1. Reference task
illustration.
4.1.2 The subject experiemental activity. The
subject sits at the round table and listens to the instructions. After haptically
exploring the layout of the six elements on the first sheet without any time
limit, he has toreproduce the first configuration on the two other empty
sheets. The main point is that this spatial layout reproduction has to be in
reference to absolute space and not to body position. So after exploring the
first board with the pieces, the subject rotates 90° round the table and
manually reproduces the configuration on the second board. He does the task
twice.
4.1.3 Collect of results. Since
the beginning the subject knows that results depend on the correct positioning
of the pieces on the grid drawn on the sheet. The further the magnetic
piece is situated away from the correct position, the more important mistake.
On the one hand, in order to observe the subject’s haptic exploration
strategies, the tasks are videotaped. Visualization allows us to identify the
different haptic exploratory patterns the subject uses. On the other, in order
to try to study the cognition of the subject, he is asked to verbalize his
reasoning.
The
interpretation of this experiment consists in comparing the differences between
performance before and after learning the cardinal points. This aims at
evaluating the impact of our cardinal strategy in training.
4.2 Training
Tasks
The cardinal
training consists of three training sessions. All the while the subject
could use a tactile compass. We continue the training until the subject is
successful.
4.2.1 Task one: Cardinal Orientation question. The
cardinal orientation question task is composed of two parts. The instructor
places one magnetic piece and asks him to tell the relevant cardinal
orientation between the piece and the centre of the sheet. Then the instructor
asks questions about the cardinal orientation between two objects placed
randomly on the table. After each answer, the subject is given feedback by the instructor. The answers can
be north, south, east, and west; northwest, southeast or north-northwest,
east-southeast… After one correct answer, the subject stands up and walks a 90°
rotation before sitting down in front of the next sheet. The instructor
questions him about the cardinal orientation of another magnetic piece and
stops after three corrects consecutive answers. At the end of this task, we can
assume that the subject has internalised cardinal map representation.
4.2.2 Task two: Cardinal Orientation positionning. This
task consists in positioning elements around the center according to the
instructor’s request. In the second part of the task, the subject is asked to
place two objects on a cardinal axis such as southeast northwest for example.
At the end of this task, we assume that the subject is able to apply his
cardinal map representation to the physical environment. Thus the subject can
now make use of cardinal orientation positioning.
4.2.3 Task three: spatial layout production. The
subject puts the six pieces wherever he likes on one sheet. Afterwards he has
to do it again on the other two sheets. In this final task, we attempt to
enable the subject to get into the habit of building his own favorite constants
in the exocentric cardinal reference frame. For example, using the
northwesterly corner as a reference point seems to be efficient.
When the
previous three tasks are successfully completed, we have to wait one week
before asking our subject to perform the reference task anew in order to avoid
the straight recall effect of learning (Schmidt,
1975).
5. RESULTS
Before
cardinal training, the subject had made seven mistakes. From a strategy point
of view, on the one hand we clearly identified “home-base-to-object”, “cyclic”
and “grid” egocentric patterns of haptic exploration and on the other, the
“perimeter-to-object” exocentric strategy appears. In other words, the subject
uses mostly egocentric spatial representation.
Some other
behavioral cues emphasized this assumption. The video recording showed
egocentric behaviour during the spatial layout reproduction task before
cardinal learning. The subject tried to turn the board in front of him before
performing. As this was not allowed, he first used body references and put the
pieces in wrong squares and then changed their position along with a slight
body contortion. This allows us to think that the subject was still using a
body referent frame.
After cardinal
training, the subject made no mistakes. He used three exocentric haptic
exploration patterns: “perimeter to object”, “back-and-forth” and “object to
object”; and only one egocentric strategy: “home base-to-object” haptic
pattern.
After this
cardinal points training, we observed the subject’s exocentric behavior.
Firstly, because he thought aloud we were able to examine a part of his spatial
cognitive process based on the cardinal orientation. As wehad expected, the
subject only spoke about cardinal orientation. For example, he said that the
triangle was in “the northwesterly corner” instead of “the top left corner”.
Secondly, he placed objects straight in the right position without body
contortion. He seemed to make mental rotations in an easier way. Consequently
this allows us to think that the subject encoded the location of the pieces in
the spatial layout using an exocentric reference frame. We found these results
although based on only one subject very revealing.
6. DISCUSSION
According to the previous non-visual spatial
theories (Thinus-Blanc, 1997) (Hil et al, 1993) (Ungar, 2000), exocentric
reference provides a higher spatial cognitive level. The cardinal concept seems
to put the blind at an even more superior spatial cognitive level. As we have
already seen, the compass provides available external cues (Lloyd, 2000)
regardless of the subject’s body position. We noticed that the subject used the
tactile compass only during the first three minutes of the cardinal training
but he kept answering questions about the cardinal orientations. Moreover,
reaction times of the answers decreased as the training went on. This evidence
supports the assumption that the subject succeeded in internalizing cardinal
points in a map representation. In accordance to Vygotsky’s theory, a tactile
compass, as psychological instrument, reorganizes spatial cognition for our
subject.
Eventually, we may take patterns on
Thinus-Blanc’s model of “two level spatial processing” in order to provide an explanation
of spatial cognition. Our subject first used simple means to encode information
in order to get acquainted with the environment. Consequently, the position
of the north has been encoded from body reference. However to learn the
other cardinal points specific maps are needed. The internalisation of the
relationships between the north indicated by the compass and the different
cardinal points proves the validity of exocentric organization as a context
situated representation of the space.
7. EXPERIMENT CONCLUSION
We do not have the ambition to explain the
general spatial cognition of the blind. Our point is to understand how tactile
compass must be used in order to afford exocentric reference frame (cf.
picture 4). The previous theories and results lead us to think that our
subject first touched the compass with egocentric haptic patterns (1) in order
to encode the north direction in a body reference frame (2). After this, he
associated egocentric north with exocentric cardinal map (3) stocked in
long-term memory. Then he was able to use haptic exocentric strategies (4) in
order to encode spatial relationships between elements (5) in a situated
cardinal representation (6) on a cognitive map.
Figure 4 . Cardinal strategy in blind condition: From
egocentric pattern to exocentric haptic pattern.
The evidence collected in this experiment
supports the assumption that the use of a compass solicits exocentric patterns
of exploration.
8. LIMITS AND PERSPECTIVES
We have
reservations about our conclusion because of our population characteristics.
Our single subject is adventitioulsy blind and is familiar with compasses, maps
and sailing.On the contrary, the congenitally or adventitiously blind often
have very little experience of maps and compasses. Thus our conclusion remains
a hypothesis. However, we are currently conducting this experiment with twenty
blind people including an experimental group and a control one. Before
concluding this experiment we will emphasize that this study is a preliminary
work for a more ambitious future project financed by CECIAA enterprize in CERV.
In fact our aim is to understand better the spatial cognition of the blind in
order to create spatial virtual reality navigation tools for them. Our
experiment remains in manipulatory space, however questions about transfers
between maps and largescale environment are involved. Can cardinal strategy
training help blind people to improve their spatial autonomy?
How relevant
is cardinal strategy for us to conceive our haptic and vocal maritime software?
9. HAPTIC AND VOCAL SIMULATOR FOR
BLIND SAILORS
Usually,
spatial representations can be indirectly built by symbolic media such as
cartographic maps (Richardson et al, 1999). Sailboat orientation is not
conceivable without maps and compasses. Even maritime spatial representation of
sighted people is necessarily organized with psychological instruments.
One particular
spatial feature of sailing consists in tacking when the destination is in front
of the wind. When sailors zigzag, they do not follow a route but realize
spatial inference tasks. In other words, if they want to reach point A, they
first sail towards an imaginary point B and wait a short time and turn. This is
a very a difficult situation to explain orally while the boat is heeling. Moreover,
if the crew encounter rocks in their path, blind people can no longer remain at
the helm. Today, accurate information is available by the means of G.P.S.
(Global positioning system). However, map knowledge is required if the sailor
wants to control his voyage, coordinates, bearings, distances and waypoints. In
this respect, we are devoting our work to create cartographic software that
will enable blind people to learn mapping and prepare trajectories.
“Most users
would prefer to access tactile maps at home” (Rowell et al, 2005), that’s why
we are setting up cartographic sailing simulators for blind sailors. They will
be able to sail virtually with cartographic and wind constraints. Wind element
and sailing principles are not complex but it is more difficult to use them in
egocentric spatial representations. Our first step will be to find an easier
way to teach maritime mapping - and not only maritime routing.
For a long
time, sailors have employed cardinal references in order to find their way on
the sea. That is why we think that our previous cardinal training task may be
revised and reinvested in this project. The simplest means to test cardinal
strategy and haptic exocentric patterns of exploration is to introduce a haptic
device in this cartographic software. A haptic device is a “mechanical system
that senses forces in remote environments and delivers those forces to the hand
of the user in the form of a haptic display accessed via a rigid link” (Lederman
et al, 2004). Phantom is a cheap
available haptic device. Regarding spatial maritime layout, we will mix haptic
object identification and cardinal vocal announcements. For example, blind
sailors will touch a buoy and automatically hear its name. After this, if blind
sailors click with the Phantom on
another object, the announcement of cardinal orientation between these two
points will be vocally announced. This is the back-and-forth haptic exocentric
strategy (Thinus-Blanc, 1997) of exploration using cardinal reference. We hope
blind sailors will develop new efficient strategies on this virtual sea.
We conclude maps
would be better serve if used with conjunction with other multimodal devices
that provide alternative sensory inputs.
Next summer,
our experimentation will begin. Blind people will explore a virtual map of “the
Rade of Brest” by touch. Another purpose is to find how to represent the
different elements of navigation charts more intuitively. The touch of the sea
will be soft and smooth, the earth will be rugged and in relief, the sailboat
will be a mobile triangle, the depth will speak when you click on it, etc… Only
blind sailors will tell us what works and what does not. Eventually both
sighted and blind people will be able to dream together about feeling the ocean
currents, the movements caused by the swell, and one day perhaps in this
virtual environment we will all be able to touch a shoal of fish swimming sixty
feet under the boat!
10. REFERENCES
J. Piaget
& B. Inhelder. La représentation de l’espace chez l’enfant, p543, Paris, PUF, 1948.
J. M.
Tellevik. Influence of spatial exploration patterns on cognitive mapping by
blindfolded sighted persons. Journal of Visual Impairment & Blindness, 86,
221-224. 1992.
E.W. Hill, J. J. Rieser, M.M. Hill &
J.Halpin. How persons with visual impairments explore novel spaces: Strategies
of good and poor performers. Journal of Visual Impairment and Blindness. 87
(8). 1993.
C.
Thinus-Blanc & F. Gaunet. Representation of space in Blind persons: Vision
as a spatial sense. Journal of Visual Impairment and Blindness. 121, 1, 20-42.
1997.
J.F. Fletcher.
Spatial representations in blind children. Development compared to sighted
children. Journal of Visual Impairment and Blindness, 74 , 381-385. 1980.
S. Millar.
Understanding and representing space: theory and evidence from studies with
blind and sighted children. Oxford. Oxford University Press. 1994.
J. O'Keefe
& L. Nadel. The Hippocampus as a cognitive map.
R. Lloyd.
Understanding and learning maps. In Kitchin, R.M. and Freundschuh,
S. (Eds) Cognitive Mapping: Past, Present and Future. Routledge, London. 2000.
G. Revesz.
Psychology and art of the blind. New York. Longmans, Green & Co. 1933.
P. Worchel.
Space perception and orientation in the blind. Psychological monographs, 65,
332, 15. 1951.
J. Juurmaa. An
analysis of the components of orientation abilityand mental manipulation of
spatial relationships. Helsinski, Finland: Institute of occupational health.
1965.
R.M. Kitchin, & R.D. Jacobson, (1997). Techniques
to Collect and Analyze the Cognitive Map Knowledge of Persons with Visual
Impairment or Blindness : Issues of Validity. Journal of Visual Impairment and
Blindness, 91 (4), 360-376.
J.J. Rieser, D.A. Guth and E.W. Hill. Sensitivity to
perspective structure while walking without vision. Perception. 15(2):173-88.
1986.
R.L. Klatzky.
Allocentric and egocentric spatial representations: Definitions, distinctions,
and interconnections. In C. Freksa, C.
Habel, & K. F. Wender (Eds.), Spatial cognition - An interdisciplinary approach
to representation and processing of spatial knowledge (Lecture Notes in
Artificial Intelligence 1404) (pp. 1-17).
Y. Hatwell,.
Psychologie cognitive de la cécité précoce.
Y. Hatwell, A.
Streri & E.Gentaz. Toucher pour connaître.
M.N.
Avraamides, J.M. Loomis, R.L. Klatzky & R.G. Golledge. Functional equivalence of spatial representation derived from vision and
language : evidence from allocentric judgements. Journal of experimental
psychology : learning, memory and cognition. 30, 4, 801-814. 2004.
M. Carreiras & B. Codina. Spatial cognition of Blind and Sighted:
visual and amodal hypothesis, Cahier de Psychologie Cognitive , vol. 12, 1,
51-78. 1992.
S. Ungar. Cognitive mapping without visual experience.
In Kitchin, R.M. and Freundschuh, S. (Eds) Cognitive
Mapping: Past, Present and Future. Routledge, London. 2000.
V.R. Schinazi.
Spatial representation and low vision: two studies on the content, accuracy and
utility of mental representations. CASA Working Papers, no.93. Working paper.
Centre for Advanced Spatial Analysis (UCL),
L.P. Acredolo, H.L. Pick & M.G. Olson.
Environmental differentiation and familiarity as determinants of children
memory for spatial location. Developmental Psychology, 50, 1062-1070. 1975.
R.A. Schmidt. A schema theory of discrete motor skill
learning. Psychologial Review, 82, 225-260. 1975.
A.E. Richardson, D. Montello & M. Hegarty. Spatial
knowledge acquisition from maps, and from navigation in real and virtual
environments. Memory & Cognition,
27, 741–750. 1999.
J. Rowell
& S. Ungar. Feeling our way: tactile map user requirements – a survey.
International Cartographic Conference,
S.J. Lederman,
& R. L. Klatzky, Haptic identification of common objects: Effects of
constraining the manual exploration process. Perception &
Psychophysics, 66, 618-628. 2004.