4032 28 HH Bülthoff S Gillner HA Mallot R Ulrich 95 3 HA Mallot S Gillner 2000-01-00 1 29 43 55 Perception The use of landmark information in a route-navigation task has been investigated in a virtual environment. After learning a route, subjects were released at intermediate points along the route and asked to indicate the next movement direction required to continue the route. At each decision point, three landmarks were present, one of which was viewed centrally and two which appeared in the periphery of the visual field when approaching the decision point. In the test phase, landmarks could be replaced either within or across places. If all landmarks combined into a new place had been associated with the same movement direction during training, subjects performed as in the control condition. This indicates that they did not need to recognise places as configurations of landmarks. If, however, landmarks that had been associated with conflicting movement directions during training were combined, subjects' performance was reduced. We conclude that local views and objects are recognised individually and that the associated directions are combined in a voting scheme. No evidence was found for a recognition of places as panoramic views or configurations of objects. no notspecified http://www.kyb.tuebingen.mpg.de//fileadmin/user_upload/files/publications/pdf95.pdf published 12 15017 15422 231 3 S Gillner HA Mallot 1998-07-00 4 10 445 463 Journal of Cognitive Neuroscience Spatial behavior in humans and animals includes a wide variety of behavioral competences and makes use of a large number of sensory cues. Here we studied the ability of human subjects to search locations, to find shortcuts and novel paths, to estimate distances between remembered places, and to draw sketch maps of the explored environment; these competences are related to goal-independent memory of space, or cognitive maps. Information on spatial relations was restricted to two types: a visual motion sequence generated by simulated movements in a virtual maze and the subject's own movement decisions defining the path through the maze. Visual information was local (i.e., no global landmarks or compass informa tion was provided). Other position and movement information (vestibular or proprioceptive) was excluded. The amount of visual information provided was varied over four experimental conditions. The results indicate that human subjects are able to learn a virtual maze from sequences of local views and movements. The information acquired is local, consisting of recognized positions and movement decisions associated to them. Although simple associations of this type can be shown to be present in some subjects, more complete configurational knowledge is acquired as well. The results are discussed in a view-based framework of navigation and the representation of spatial knowledge by means of a view graph. no notspecified http://www.kyb.tuebingen.mpg.de//fileadmin/user_upload/files/publications/pdf231.pdf published 18 15017 15422 530 3 HA Mallot S Gillner PA Arndt 1996-01-00 2 74 95 106 Biological Cybernetics One possible strategy for the solution of the correspondence problem of stereo matching is the coarse-to-fine mechanism: The matching process starts with a lowpassfiltered version of the stereogram where only a few, high-contrast image features can be extracted and the probability of false matches is therefore low. In subsequent stages, information from higher spatial frequencies is used gradually to improve the correspondence data obtained on the coarser scales. Coarse-to-fine strategies predict that information from coarse scale is used to disambiguate matching information on finer scales. We have tested this prediction by means of the wallpaper illusion using periodic intensity-profiles with different matching ambiguities on different spatial scale. Our psychophysical experiments show (i) that unambiguous information at coarse scale is not always used to disambiguate finer scale information, (ii) that unambiguous fine-scale information can be used to disambiguate coarsescale information and (iii) that low spatial frequency is more efficient for disambiguation than higher frequency. We conclude that the human stereo vision system does not always proceed from coarse to fine. As an alternative scheme for scale-space integration, we discuss more symmetric schemes such as maximum likelihood combinations of data from different channels. no notspecified http://www.kyb.tuebingen.mpg.de/ published 11 15017 15422 206 7 HA Mallot S Gillner SD Steck MO Franz Stade, Germany1999-08-00 367 380 International Conference on Spatial Information Theory: Cognitive and Computational Foundations of Geographic Information Science (COSIT '99) The simplest representation of space allowing for spatial cognition in biological and artificial systems is a graph; the nodes of this graph contain local position information (views) chracterizing certain places while its links are labeled with movements or actions leading from one view to the next. In this paper, we review recent theoretical and psychological 2ork on view-graph representations. In particular, we will focus on the transition from stereotyped "recognition-triggered responses" to a graph-like cognitive map where the recognition of a view allows to choose one of several responses. We will present psychophysical evidence from experiments using virtual reality indicating that human subjects do make use of simple view-movement associations without recognizing places. This mechanism is not restricted to navigation in mazes but can be extended to large-scale open environments by means of an additional guidance mechanism. As compared to more map-like approaches such as occupancy grids or survey-maps, the view-graph is less computationally expensive and can easily be adapted to the coarseness of spatial knowledge. no notspecified http://www.kyb.tuebingen.mpg.de/ published 13 15017 15422 452 7 S Gillner HA Mallot Hamburg, Germany1996-03-00 43 45 2. Kognitionswissenschaftliche Tagung (KogWis96) no notspecified http://www.kyb.tuebingen.mpg.de/ published 2 15017 15422 343 2 HA Mallot S Gillner H-J van Veen HH Bülthoff Springer Berlin, Germany 1998-00-00 447 467 Spatial Cognition: An interdisciplinary approach to representing and processing spatial knowledge Virtual reality is used as a novel tool for behavioral experiments on humans. Two environments, Hexatown and Virtual Tübingen, are presented. Experiments on cognitive maps carried out in the Hexatown environment are reported in this paper. Results indicate that subjects are able to acquire configuration knowledge of the virtual town even in the absence of physical movement. Simpler mechanisms such as associations of views with movements are also present. We discuss the results in relation to a graph-theoretic approach to cognitive maps. no notspecified http://www.kyb.tuebingen.mpg.de//fileadmin/user_upload/files/publications/behavioral_experiments_in_spatial_cognition_using_vr_343[0].pdf published 20 15017 15422 1532 46 HA Mallot S Gillner 1998-10-00 1998-10-00 View-based vs. place-based navigation: What is recognized in recognition-triggered responses? no notspecified 15017 15422 1510 46 S Gillner HA Mallot 1997-02-00 1997-02-00 Navigation and Acquisition of Spatial Knowledge in a Virtual Maze no notspecified 15017 15422 1459 46 HA Mallot S Gillner PA Arndt 1994-03-00 1994-03-00 Is Correspondence Search in Human Stereo Vision a Coarse-to-Fine Process? no notspecified 15017 15422 277 7 SD Geiger HA Mallot S Gillner Tübingen, Germany1998-02-00 75 1. Tübinger Wahrnehmungskonferenz (TWK 98) Spatial behavior in humans and animals includes a wide variety of behavioral competences that make use of many sensory cues, including vision. The visual input contains various cues about the observers current position (e.g., from views and local landmarks), the compass direction (e.g., provided by global landmarks), and egomotion (e.g., from optic flow). Here we investigate the role of global vs. local landmarks in a route finding task. If navigation relies more on ‘global’ landmarks for a route finding task then an allocentric description should be remembered; such as “When you reach the church square, go towards the tower on the mountain”. Alternatively, ‘local’ landmarks could guide navigation decisions by view-movement associations; e.g. “When you come to the church, turn right”. Evidence for the last strategy was presented by Gillner and Mallot (Journal of Cognitive Neuroscience, in press). We performed an experiment in a virtual environment called “Hexatown”. Hexatown consists of a regular hexagonal grid of junctions joined together by streets. At each junction there are three buildings, or other objects. Additionally, we provide global direction or compass information by placing six global landmarks distributed equally on a mountain range surrounding Hexatown. Subjects navigated in Hexatown by pressing the buttons of a computer mouse. According to their movement decisions, egomotion was simulated. Subjects had to learn the route back and forth between two specific buildings. Awareness of global landmarks was assessed by an additional pointing task. In the test-phase individual junctions were approached and the subjects’ movement decision was recorded. Two conditions were used: a ‘consistent’ condition, which was the same as in the training phase, and a ‘conflict’ condition. Conflict was produced by transposition of objects such that the global and local strategies predicted different movement decisions. In the consistent condition, i.e., with unchanged objects, 20 subjects made 85% correct decisions out of a total of 160. In the conflict condition, 77% of the decisions were in agreement with the local and 23% with the global strategy. This supports our previous finding that local views play a dominant role in making route judgements. In a control experiment we tested whether subjects could use the global landmarks at all. We reduced the local information in the maze and instructed the subjects to attend to the global landmarks. In this case, 76% of the 80 decisions were consistent with global landmark information. Since no local information was provided in this control experiment the remaining 24% of the decisions were errors. We conclude that subjects prefer local landmarks when available, but are also able to use global landmarks for route finding, when they are instructed to attend to them. no notspecified http://www.kyb.tuebingen.mpg.de/ published -75 15017 15422 282 7 HA Mallot S Gillner SD Geiger Tübingen, Germany1998-02-00 33 1. Tübinger Wahrnehmungskonferenz (TWK 98) In the development of navigation behavior, one important step is the transition from routes to maps. Route behavior is characterized by the repetition of previously learned sequences of sensory input and performed movements and can be modeled by chains of stimulus-response-stimulus (SRS) associations. The current view (“local position information”) elicits a movement decision from which in turn the next view may be expected. For each goal, the whole route has to be learned and stored, even if routes to different goals share common segments. Map behavior makes use of goal independent knowledge of the spatial layout of the environment; such knowledge is usually called a cognitive map. In a series of experiments using virtual reality technology, we investigated the navigation ability of human subjects. The maze was composed of streets forming a regular hexagonal grid and buildings placed at the junctions in the angles between the streets (“Hexatown”). Subjects performed simulated movements by hitting the buttons of a computer mouse. Movement started and ended at so-called decision points, i.e. the junctions of the streets. Pure turns could be performed in steps of 60 degrees. When looking into a street, a translation down that street could be performed that ended at the next junction. Subjects were released at some junction and had to find various buildings presented to them as a printout on a sheet of paper (see Gillner and Mallot, J. Cogn. Neurosci., in press). In the talk, we will review a number of experiments performed in the Hexatown environment. With respect to the route vs. map dichotomy, three important results have been obtained: 1. Persistence: Subjects tend to repeat movement decisions when coming back to a previously visited view. This is evidence for simple stimulus-response associations as would be expected in route memory. 2. View-based representation: After learning a given route, we replaced individual buildings along that route. Results indicate that movements are associated to views of individual buildings, not to configurations of buildings at each junction (“places”). 3. Transfer: Subjects were able to transfer knowledge from one route to another. This is an indication of goal-independent knowledge (cognitive map). In conclusion, the data show that humans simultaneously use both route and map type knowledge of the environment. A common framework for the two types of knowledge based on the view-graph (Schölkopf and Mallot, Adaptive Behavior 3:311-348, 1995) will be discussed. no notspecified http://www.kyb.tuebingen.mpg.de/ published -33 15017 15422 407 7 SD Geiger S Gillner HA Mallot Helsinki, Finland1997-08-00 56 20th European Conference on Visual Perception Motivated by the results of Gillner and Mallot (1996 Perception 25 Supplement, 93) implying that local views are basic elements for a spatial representation, we studied the role of global versus local landmarks using a route-finding task. Our hypotheses were: (i) A global navigation strategy relying on allocentric movement decisions is used, eg "go from this place towards the chapel on the hill", or (ii) a local navigation strategy based on view--movement associations is used, eg "at the red building go right". We performed an experiment in a computer graphics town based on a hexagonal grid structure. At each intersection we placed three different buildings. We also provided global direction information by placing six global landmarks distributed equally along a mountain range. Subjects had to learn the back and forth route between two buildings, not knowing that after a learning phase the location of buildings at a particular junction would be changed. These changes produced conflicting global and local information. In the test-phase, the subject approached individual junctions in both learned and novel directions and the movement decisions were recorded. In a control condition with unchanged places twenty subjects made correct decisions for 136 of 160 movements. In the experimental conflict condition 123 decisions were consistent with a local and 37 with a global strategy. This supports our previous finding that local views play a dominant role in making route judgements. Approaching a junction from a learned direction leads to more accurate movement decisions than approaching it from a novel direction, even if the global landmarks are available, which provides further support for the local-view hypothesis. no notspecified http://www.kyb.tuebingen.mpg.de/ published -56 15017 15422 406 7 SD Geiger S Gillner HA Mallot Göttingen, Germany1997-05-00 993 25th Göttingen Neurobiology Conference no notspecified http://www.kyb.tuebingen.mpg.de/ published -993 15017 15422 415 7 HA Mallot S Gillner Fort Lauderdale, FL, USA1997-05-00 1007 Annual Meeting of the Association for Research in Vision and Ophthalmology (ARVO 1997) no notspecified http://www.kyb.tuebingen.mpg.de/ published -1007 15017 15422 571 7 S Gillner HA Mallot Strasbourg, France1996-09-00 93 19th European Conference on Visual Perception no notspecified http://www.kyb.tuebingen.mpg.de/ published -93 15017 15422 572 7 S Gillner HA Mallot Göttingen, Germany1996-05-00 774 24th Göttingen Neurobiology Conference no notspecified http://www.kyb.tuebingen.mpg.de/ published -774 15017 15422 441 15 S Gillner 1997-00-00 no notspecified published 15017 15422