PCR and DNA Sequencing

Mathieu Simonnet, MSc, Jean-Yves Guinard, PhD and Jacques Tisseau, PhD

European Center for Virtual Reality (C.E.R.V.), France

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 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. Can blind people be helped to construct more effective spatial pictures? Prior works have shown that strategies are the most important factors in spatial performance in large-scale space. 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 to explore tactile maps and to 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 to help the blind improve their spatial cognition.

Keywords: non-visual representation, space, haptic exploration, strategy, virtual geographic map, blind sailors, France

Correspondance: Mathieu Simonnet, European Center for Virtual Reality, 25 rue Claude Chappe, 29280 Plouzané, France. E-mail: [email protected]

Submitted: January 15, 2006. Revised: February 02, 2006. Accepted: February 03, 2006.

INTRODUCTION systematical training with a compass. The analysis of these This paper describes how we are taking into account results focuses on the haptic exploration strategies. blind people’s spatial cognition to conceive simulation In the future, we shall consider the essential question of software for blind people’s navigation on a virtual sea (1-4). the interest of cardinal strategy for transferring spatial Different spatial theories accord various spatial capacities to capacities between maps and environment. Our position is blind people (4). We know, however, that “the main that virtual reality can help blind people to connect micro characteristic of spatial representations is that they involve and macro scales in the same exocentric reference frame. the use of reference” (5). The lack of sight tends to lead to a body centered spatial frame, but maps are external reference NON VISUAL SPATIAL THEORIES frames (6). How can we make exocentric reference easier After a survey of debates about non-visual representation for blind people when they encode space? during the last century, we are going to emphasize the “Search strategies in haptic exploration are related to distinction between egocentric and exocentric reference encoding processes” (2). Therefore, this statement means frames related to the lack of vision. that teaching blind people exocentric representation should help them use haptic exploration strategies more effectively. History Exocentric strategies aim at locating object to object How do blind people build efficient space representations? regardless of the person’s body position. This top-down During the twentieth century, different theories tried to reasoning appeals to the cognitive level in the first place and answer this question, and many controversies about the role to the sensory-motor level in the second place. of previous visual experience appeared. According to the As the north is the prior knowledge acquired by map- inefficiency theory (9), blind people are able to build readers (7,8), we taught blind people that the concept of unified space representations only from simple forms or cardinal points is an absolute exocentric reference. Thus, we elements. The results of a wooden blocks recognizing task made them practice reasoning about the cardinal concept to show that “touch alone is not as efficient in the perception build exocentric spatial representations. According to of (…) complex tactual form relationships as touch aided by Vygotsky’s socio-cultural theory (1896-1934), psychological visual images” (10). The results of a second experiment instruments like writing and maps are able to reorganize about direction estimations in a triangle completion task individual cognition. The compass is one of them. After leads us to conclude that kinesthetic cues were better able to testing our spatial reference task, we have experimented perform when translated into visual images (10).

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The difference and inefficiency theories disagree. the role of the compass on spatial representation. Fletcher assumes that previous results come from a testing artifact (5). Other experiments showed no difference between The known strategies blindfolded and congenitally blind adults when they were Tellevik (2) first tested three patterns of non-visual dealing with material that was not “optically familiar” (11). exploration. In this task, blindfolded subjects had to find Eventually, “lack of vision slows down ontogenic spatial objects in a large-scale environment. Using “perimeter” development…but does not prohibit it” (12). patterns, the subjects explored the boundaries of given area. To conclude, we have to remember that during a spatial In “gridline” patterns, the subjects investigated internal inference task, congenitally blind people performed as well elements of the area to learn their spatial relationship. With as blindfolded (13). So, the congenitally blind persons are using “reference-point” patterns, the subjects relate their able to construct spatial cognitive maps but this capacity exploration to salient elements. The results show that search develops more slowly. The question is how the lack of vision strategy in haptic exploration may be differentially related slows down the construction of exocentric representation. to encoding processes. With “perimeter” and “gridline” patterns it was more difficult for the blind to change their From egocentric to exocentric reference perspective than with “reference-point” strategies. This result shows that the latter pattern is more exocentric than Exceptions notwithstanding, there is general under- the others. So, we think “gridline” patterns do not really standing that in an egocentric reference frame, locations give information about the relation between elements. are represented with respect to the particular perspective of Consequently, the “gridline” pattern is an egocentric a perceiver, whereas an allocentric reference frame locates strategy. points within a framework external to the holder of the One year later, Hill (3) emphasized a lack in literature representation and independent of his or her position (14). about object-to-object relationships. In a direction-estima- tion task about the explored environment, the results showed Vision is the first perceptive modality of data concerning that “perimeter” pattern is a “self-to-object” strategy. spatial environment (15). Vision gives simultaneously Furthermore, an “object-to-object” pattern is identified and varied information about objects and their configuration in linked to distance between object reasoning. Eventually an distant space. In addition to visual modality, haptic or efficient chronology of these patterns seems to involve tactile-kinesthetic modality informs well about spatial “perimeter” and “object-to-object” strategies. layout (16). The sequential characteristic of haptic modality In this respect, Thinus-Blanc (4) studied the correlation leads blind people to encode an environment in successive between exploration patterns and spatial performance in reference to their own body before executing spatial locomotion and handling space. Subjects without vision have inference between external objects. Nevertheless, vision is to detect the changes in a previously explored spatial layout. neither necessary nor sufficient for spatial coding (6). The same two types of patterns of explorations are found in According to the Piagetian theory (1), during their small and large-scale space. On the one hand, “cyclic development children construct external reference frames patterns consist in visiting a sequence of objects, with the from egocentric reference in coordinating vision and tactile same one beginning and ending the cycle”. On the other, “the perception. When using haptic modality, blind people have back-and-forth pattern is characterized by repeated to remember the different segments of the object as a whole trajectories between two places”. In accordance with the in short-term memory. This cognitive effort allows them to O’Keefe and Nadel (7) theory, the similarity between the first construct unified exocentric representation of space (17.). In type of strategy and route knowledge and the second type and this respect, a recent experiment shows that “allocentric map knowledge let us emphasize that “cyclic” pattern is an (exocentric) relations can be accurately reported in all egocentric reference frame and “back-and-forth” pattern is an modalities […]” (18). Thus, spatial representation is not exocentric frame of reference. Here the results verify the limited to any particular sensory modality, although the superiority of exocentric reference frame. processing is probably faster with vision. To summarize the research, Ungar (19) carried out a To conclude, not all blind people really build an literature survey of cognitive mapping without visual external frame of reference but are able to do so. experience. A synthesis of non-visual exploration patterns Differences in coding strategies are implicated more than identifies seven distinct exploration strategies or patterns: their capacities of spatial perception (6). home base-to-object, perimeter, grid, cyclic, perimeter-to- object, back-and-forth, and object-to-object strategies, HAPTIC EXPLORATION STRATEGIES which are summarized in Table 1. Since the 1990s, researchers have correlated exploration Recently, a doctoral thesis about “perception and patterns with the nature of non-visual spatial representation. cognition of space by individuals who are blind or have low Evidence of exocentric reference superiority leads us to use vision” introduced a new strategy called “perimeter-to- semantic representation to help blind people to improve center” (20). The subjects explored a constructed maze, and encoding processes. We will present our hypothesis about located and remembered the positions of six different salient HAPTIC NAVIGATION SOFTWARE FOR BLIND SAILORS 63

Table 1. Ungar (19) modified table: Nature of strategies identified in Hill et al (3); Thinus-Blanc (4); Schinazi (20)

Strategy Description Nature Moving repeatedly between the home base (origin point Home base-to-object (3) Egocentric for exploration) and all the others in turn Explored the boundaries of an area to identify the area's Perimeter (3) shape, size and key features around its perimeter, by Egocentric walking along the edge of the layout Investigated the internal elements of an area to learn their Grid (3) spatial relationships, by taking straight-line paths from one Egocentric side of the layout to the other. Each of the four objects visited in turn, and then returning Cyclic (4) Egocentric to the first object explored the boundaries to identify the area’s shape, size Perimeter to center (20) Egocentric and key features around the perimeter and then inside of it Perimeter to object (3) Moving repeatedly between an object and the perimeter Exocentric Back-and-forth (4) Moving repeatedly between two objects Exocentric Moving repeatedly from one object to another, or feeling Object to object (3) the relationship between objects using hand or cane. Exocentric

points. The results emphasize two egocentric strategies: Why not teach blind people cardinal points concept? “grid” and “perimeter-to-center”. The first strategy consists in Acredolo et al. (21) explain, “information related to the exploring the boundaries to identify the shape, size, and key immediate goal of an action is remembered more effectively features of the area around the perimeter and then the inside than is information that is not” (2). In this respect, we ask of it. We have added this egocentric strategy in Table 1. our blind subject to remember spatial layout using cardinal All these strategies come from movement observations. points reference. This learning requires the use of a tactile The results show that blind people performed better when compass to provide salient external cues. We conducted an they used exocentric patterns. This evidence proves the exploratory experimentation to evaluate the efficiency of positive correlation between a higher cognitive spatial level cardinal reference in space encoding. and exocentric strategies. EXPERIMENT The cardinal strategy: a top-down process As we have already seen, egocentric and exocentric spatial A coherent relation between mental representation and representations exist. This experiment attempts to observe if sensorial information provides a semantic encoding. Thus, the compass leads to the use of haptic exocentric patterns of the exocentric or egocentric nature of previous spatial exploration. At the moment, the subject of our exploratory strategies results from cognitive processes. The top-down experimentation is an adventitiously blind individual. The process, from the map concept to environment stimuli and man who is 45 years old, lost his sight at the age of 22. He the bottom-up process tightly fit into each other. agreed to be the first to test the following protocol. Subjects without vision have the same stimuli at their disposal. As they do not perform similarly, blind subjects ReferenceTask probably do not use the same mental space concept. How The spatial task consists in reproducing a small-scale spatial can we induce blind people to use maps as representations? layout in an absolute reference after changing position Cognitive mapping processing requires external cues in around a table. long-term memory. We know that “the fact that the information which is reliably available in long-term prior  Situation. Three square metal sheets are placed at experience influences modes of coding explains coding in three different points, 90° rotated around the table. blind conditions” (6). As we have already seen, the The sheets are twenty-five centimetres wide. We use cognition of the north is one of the key prerequisites to six magnetic pieces of various geometric shapes such reading a map. as a triangle, a cross, a trapezium, a disk, a half-disk 64 M SIMONNET, J-Y GUINARD AND J TISSEAU

continue the training until the subject is successful.

 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 receives feedback from the instructor. The answers can be north, south, east, and west; northwest, southeast or  north-northwest, east-southeast… After one correct Fig. 1: Reference task illustration answer, the subject stands up and walks a 90° rotation and a square. Each piece is covered with different before sitting down in front of the next sheet. The textures: soft, rough, wire netting, cardboard, tactile instructor questions him about the cardinal orientation lines and crossed tactile lines. All this aims at helping of another magnetic piece and stops after three the subject to distinguish all these different objects corrects consecutive answers. At the end of this task, from each other. The pieces are placed only on the we can assume that the subject has internalised cardinal first sheet; on the other two, they are placed next to map representation. them. A non-tactile gridline is drawn on this handling  Task two: Cardinal Orientation positionning. This space. Each magnetic piece is placed in the middle of task consists in positioning elements around the center a five centimeter non-tactile square. The grid lines according to the instructor’s request. In the second allow us to measure errors when the blind subject part of the task, the subject is asked to place two reproduces the layout (cf. Figure 1). objects on a cardinal axis such as southeast northwest  Subject’s experiemental activity. The subject sits at for example. At the end of this task, we assume that the round table and listens to the instructions. After the subject is able to apply his cardinal map haptically exploring the layout of the six elements on representation to the physical environment. Thus the the first sheet without any time limit, the subject has subject can now make use of cardinal orientation to reproduce the first configuration on the two other positioning. empty sheets. The main point is that this spatial layout  Task three: spatial layout production. The subject reproduction has to be in reference to absolute space puts the six pieces wherever he likes on one sheet. and not to body position. So, after exploring the first Afterwards he has to do it again on the other two board with the pieces, the subject rotates 90° round sheets. In this final task, we attempt to enable the the table and manually reproduces the configuration subject to get into the habit of building his own on the second board. He does the task twice. favorite constants in the exocentric cardinal reference  Collection of results. From the beginning, the frame. For example, using the northwesterly corner as subject knows that results depend on the correct a reference point seems to be efficient. positioning of the pieces on the grid drawn on the sheet. The further the magnetic piece is situated away When the previous three tasks are successfully completed, from the correct position, the more important will be we have to wait one week before asking our subject to the mistake. On the one hand, the tasks are videotaped perform the reference task anew to avoid the straight recall to observe the subject’s haptic exploration strategies. effect of learning (22). Visualization allows us to identify the different haptic exploratory patterns the subject uses. On the other, to RESULTS try to study the cognition of the subject, the subject is Before cardinal training, the subject had made seven asked to verbalize his reasoning. mistakes. From a strategy point of view, on the one hand we clearly identified “home-base-to-object”, “cyclic” and The interpretation of this experiment consists in comparing “grid” egocentric patterns of haptic exploration and on the the differences between performance before and after other, the “perimeter-to-object” exocentric strategy appears. learning the cardinal points. This experiment aims at In other words, the subject uses mostly egocentric spatial evaluating the impact of our cardinal strategy in training. representation. Certain other behavioral cues emphasized this assumption. The video recording showed egocentric Training Tasks behavior during the spatial layout reproduction task before The cardinal training consists of three training sessions. All cardinal learning. The subject tried to turn the board in front the while the subject could use a tactile compass. We of him before performing. As this was not allowed, he first HAPTIC NAVIGATION SOFTWARE FOR BLIND SAILORS 65 used body references and put the pieces in wrong squares tactile compass must be used to afford exocentric reference and then changed their position along with a slight body frame (Figure 2). The previous theories and results lead us contortion. This performance allows us to think that the subject was still using a body referent frame. Cardinal map Exocentric haptic patterns [4] After cardinal training, the subject made no mistakes. memory [3] He used three exocentric haptic exploration patterns: “perimeter to object”, “back-and-forth”, and “object to object”; Environment elements and only one egocentric strategy: “home base-to-object” haptic pattern. Egocentric spatial processing [2] After this cardinal points training, we observed the subject’s exocentric behavior. Firstly, because he thought Exocentric spatial processing [5] COMPASS aloud we were able to examine a part of his spatial cognitive process based on the cardinal orientation. As Situated wehad expected, the subject spoke only about cardinal cardinal Egocentric haptic patterns [1] orientation. For example, he said that the triangle was in map [6] “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 Fig. 2: Cardinal strategy in blind condition: From egocentric rotations in an easier way. Consequently, this explanation pattern to exocentric haptic pattern 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 to think that our subject first touched the compass with ego- subject, very revealing. centric haptic patterns [1] to encode the north direction in a body reference frame [2]. After this, he associated DISCUSSION egocentric north with exocentric cardinal map [3] stocked in According to the previous non-visual spatial theories (3,4), long-term memory. Then he was able to use haptic exocentric reference provides a higher spatial cognitive exocentric strategies [4] to encode spatial relationships level. The cardinal concept seems to put the blind at an even between elements [5] in a situated cardinal representation more superior spatial cognitive level. As we have already [6] on a cognitive map. Error: Reference source not seen, the compass provides available external cues (8), foundThe evidence collected in this experiment supports the regardless of the subject’s body position. We noticed that assumption that the use of a compass solicits exocentric the subject used the tactile compass only during the first patterns of exploration. three minutes of the cardinal training but kept answering questions about the cardinal orientations. Moreover, the LIMITS AND PERSPECTIVES reaction times of the answers decreased as the training went We have reservations about our conclusion because of our on. This evidence supports the assumption that the subject population characteristics. Our single subject is adventitioulsy succeeded in internalizing cardinal points in a map blind and is familiar with compasses, maps, and sailing.On representation. In accordance to Vygotsky’s theory, a tactile the contrary, the congenitally or adventitiously blind often compass, as psychological instrument, reorganizes spatial have very little experience of maps and compasses. Thus, cognition for our subject. our conclusion remains a hypothesis. However, we are Eventually, we may take patterns on Thinus-Blanc’s currently conducting this experiment with 20 blind people, model of “two level spatial processing” to provide an including an experimental and a control group. Before explanation of spatial cognition. Our subject first used concluding this experiment, we will emphasize that this simple means to encode information to get acquainted with study is a preliminary work for a more ambitious future the environment. Consequently, the position of the north has project financed by CECIAA enterprize in CERV. In fact, been encoded from body reference. To learn the other our aim is to understand better the spatial cognition of the cardinal points, however, specific maps are needed. The blind to create spatial virtual reality navigation tools for internalization of the relations between the north indicated them. Our experiment remains in manipulatory space, by the compass and the different cardinal points proves the however, questions about transfers between maps and validity of exocentric organization as a context situated largescale environment are involved (23). Can cardinal representation of the space. strategy training help blind people to improve their spatial autonomy? How relevant is cardinal strategy for us to EXPERIMENT CONCLUSION conceive our haptic and vocal maritime software? We do not have the ambition to explain the general spatial cognition of the blind. Our point is to understand how 66 M SIMONNET, J-Y GUINARD AND J TISSEAU

orientation is not conceivable without maps and compasses. HAPTIC AND VOCAL SIMULATOR FOR BLIND SAILORS Even maritime spatial representation of sighted people is Usually, spatial representations can be indirectly built by necessarily organized with psychological instruments. symbolic media such as cartographic maps (24). Sailboat

Fig. 3: From paper tactile maritime map to virtual haptic one.

One particular spatial feature of sailing consists of with the Phantom on another object, the announcement of tacking when the destination is in front of the wind. When cardinal orientation between these two points will be sailors zigzag, they do not follow a route but realize spatial vocally announced. This is the back-and-forth haptic inference tasks. In other words, if they want to reach point exocentric strategy (4) of exploration using cardinal A, they first sail toward an imaginary point B and wait a reference. We hope blind sailors will develop new efficient short time and turn. This is a very a difficult situation to strategies on this virtual sea. We conclude maps would be explain orally while the boat is heeling. Moreover, if the better served if used in conjunction with other multimodal crew encounter rocks in their path, blind people can no devices that provide alternative sensory inputs. longer remain at the helm. Today, accurate information is Next summer, our experimentation will begin. Blind available by the means of GPS (Global positioning system). people will explore a virtual map of “the Rade of Brest” by However, map knowledge is required if the sailor wants to touch. Another purpose is to find how to represent the control his voyage, coordinates, bearings, distances, and different elements of navigation charts more intuitively. The waypoints. In this respect, we are devoting our work to touch of the sea will be soft and smooth, the earth will be create cartographic software that will enable blind people to rugged and in relief, the sailboat will be a mobile triangle, learn mapping and prepare trajectories. the depth will speak when you click on it, etc… Only blind “ Most users would prefer to access tactile maps at sailors will tell us what works and what does not. home” (25), that’s why we are setting up cartographic Eventually both sighted and blind people will be able to sailing simulators for blind sailors. They will be able to sail dream together about feeling the ocean currents, the virtually with cartographic and wind constraints. Wind movements caused by the swell, and one day perhaps in this element and sailing principles are not complex, but it is virtual environment we will all be able to touch a shoal of more difficult to use them in egocentric spatial represent- fish swimming sixty feet under the boat! ations. 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 references to find their way on the sea. That is why we think 1. Piaget J, Inhelder B. La représentation de l’espace chez that our previous cardinal training task may be revised and l’enfant. Paris, France: PUF, 1948:543. [French] reinvested in this project. The simplest means to test 2. Tellevik JM. Influence of spatial exploration patterns cardinal strategy and haptic exocentric patterns of exploration on cognitive mapping by blindfolded sighted persons. is to introduce a haptic device in this cartographic software. J Vis Impair Blind 1992;86: 221-4. A haptic device is a “mechanical system that senses forces 3. Hill EW, Rieser JJ, Hill MM, Halpin J. How persons in remote environments and delivers those forces to the with visual impairments explore novel spaces: Strategies hand of the user in the form of a haptic display accessed via of good and poor performers. J Vis Impair Blind 1993; a rigid link” (26). Phantom is a cheap available haptic 87(8):295-301. device. Regarding spatial maritime layout, we will mix 4. Thinus-Blanc C, Gaunet F. Representation of space in haptic object identification and cardinal vocal announce- Blind persons: Vision as a spatial sense. J Vis Impair ments. For example, blind sailors will touch a buoy and Blind 1997;121(1):20-42. automatically hear its name. After this, if blind sailors click HAPTIC NAVIGATION SOFTWARE FOR BLIND SAILORS 67

5. Fletcher JF. Spatial representations in blind children. 17. Avraamides MN, Loomis JM, Klatzky RL, Golledge Development compared to sighted children. J Vis RG. Functional equivalence of spatial representation Impair Blind 1980;74:381-5. derived from vision and language: Evidence from allo- 6. Millar S. Understanding and representing space: theory centric judgements. J Exp Psychol 2004;30(4): 801-14. and evidence from studies with blind and sighted 18. Carreiras M, Codina B. Spatial cognition of blind and children. Oxford, UK: Oxford Univ Press, 1994. sighted: Visual and amodal hypothesis. Cahier de 7. O’Keefe J, Nadel L. The hippocampus as a cognitive Psychologie Cognitive 1992;12(1):51-78. map. Oxford, UK: Oxford Univ Press, 1978. 19. Ungar S. Cognitive mapping without visual experience. 8. Lloyd R. Understanding and learning maps. In: Kitchin In: Kitchin RM, Freundschuh S, eds. Cognitive RM, Freundschuh S, eds. Cognitive mapping: Past, mapping: Past, present and future. London, UK: present and future. London, UK: Routledge, 2000. Routledge, 2000. 9. Revesz G. Psychology and art of the blind. New York, 20. Schinazi VR. Spatial representation and low vision: NY, USA: Longmans, 1933. two studies on the content, accuracy, and utility of 10. Worchel P. Space perception and orientation in the mental representations. CASA Working Papers, no. blind. Psychol Monogr 1951;65(15):332. 93. London, UK: Centre Adv Spatial Analysis (UCL), 11. Juurmaa J. An analysis of the components of orienta- 2005. tion abilityand mental manipulation of spatial 21. Acredolo LP, Pick HL, Olson MG. Environmental relation-ships. Helsinski, SF: Inst Occupat Health, differentiation and familiarity as determinants of 1965. children memory for spatial location. Dev Psychol 12. Kitchin RM, Jacobson RD. Techniques to collect and 1975;50:1062-70. analyze the cognitive map knowledge of persons with 22. Schmidt RA. A schema theory of discrete motor skill visual impairment or blindness: Issues of validity. J learning. Psychol Rev 1975;82:225-60. Vis Impair Blind 1997;91(4):360-76. 23. Lahav O, Mioduser D. Blind persons’ acquisition of 13. Rieser JJ, Guth DA, Hill EW. Sensitivity to spatial cognitive mapping and orientation skills perspective structure while walking without vision. supported by virtual environment. Int J Disabil Hum Perception 1986;15(2):173-88. Dev 2005;4(3):231-7. 14. Klatzky RL. Allocentric and egocentric spatial 24. Richardson AE, Montello D, Hegarty M. Spatial representations: Definitions, distinctions, and inter- knowledge acquisition from maps, and from naviga- connections. In: Freksa C, Habel C, Wender KF, eds. tion in real and virtual environments. Mem Cogn Spatial cognition. An interdisciplinary approach to 1999;27:741–50. representation and processing of spatial knowledge 25. Rowell J, Ungar S. Feeling our way: tactile map user (Lecture Notes in Artificial Intelligence 1404). Berlin, requirements—a survey. Int Cartogr Conf, La Coruna, Germany: Springer, 1998;1-17. 2005. 15. Hatwell Y. Psychologie cognitive de la cécité précoce. 26. Lederman SJ, Klatzky RL. Haptic identification of Paris, France: Dunod, 2004. [French] common objects: Effects of constraining the manual 16. Hatwell Y, Streri A, Gentaz E. Toucher pour connaître. exploration process. Percept Psychophysics 2004;66: Paris, France: PUF, 2000. [French] 618-28.