The Spatial Semantic Hierarchy is a model of knowledge of large-scale space consisting of multiple interacting representations, both qualitative and quantitative. The SSH is inspired by the properties of the human cognitive map, and is intended to serve both as a model of the human cognitive map and as a method for robot exploration and map-building. The multiple levels of the SSH express states of partial knowledge, and thus enable the human or robotic agent to deal robustly with uncertainty during both learning and problem-solving. The control level represents useful patterns of sensorimotor interaction with the world in the form of trajectory-following and hill-climbing control laws leading to locally distinctive states. Local geometric maps in local frames of reference can be constructed at the control level to serve as observers for control laws in particular neighborhoods. The causal level abstracts continuous behavior among distinctive states into a discrete model ...

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We develop a model-based approach to reasoning, in which the knowledge base is represented as a set of models (satisfying assignments) rather than a logical formula, and the set of queries is restricted. We show that for every propositional knowledge base (KB) there exists a set of characteristic models with the property that a query is true in KB if and only if it is satisfied by the models in this set. We characterize a set of functions for which the model-based representation is compact and provides efficient reasoning. These include cases where the formula-based representation does not support efficient reasoning. In addition, we consider the model-based approach to abductive reasoning and show that for any propositional KB, reasoning with its model-based representation yields an abductive explanation in time that is polynomial in its size. Some of our technical results make use of the Monotone Theory, a new characterization of Boolean functions recently introduced. The notion of ...

Adults were asked to judge the self-to-object directions in a room from novel points of observation that differed from their actual point at times only by a rotation and at other times only by a translation. The results show for the rotation trials that the errors and latencies when a novel point was imagined were worse than the baseline responses from their actual points of observation, and the latencies varied as a function of the magnitude of the to-be-imagined rotation. For the translation trials, on the other hand, the errors and latencies when a novel point was imagined were comparable to the baseline responses from their actual point and did not vary significantly across the different imagined station points. The evidence indicates that subjects know the objectto-object relations directly, without going through the origin of a coordinate system. In addition, similarities in processing during imagination on the one hand, and perception and action on the other are discussed. The spatial structure of a place consists of the distances and directions relating its objects, features, and events. Observers often produce spatially coordinated action while on the move and plan actions before reaching the station points from which

Subjects read narratives describing directions of objects around a standing or reclimng observer, who was periodically reoriented. RTs were measured to identify which object was currently located beyond the observer's head, feet, front, back, fight, and left. When the observer was standing, head/feet RTs were fastest, followed by front/back and then right/left. For the reclining observer, front/back RTs were fastest, followed by head/feet and then right/left. The data support the spatial framework model, according to which space is conceptualized in terms of three axes whose accessibility depends on body asymmetries and the relation of the body to the world. The data allow rejection of the equiavailability model, according to which RTs to all directions are equal, and the mental transformation model, according to which RTs increase with angular disparity from front. Consider the following passage ("The Gambler, the Nun, and the Radio, " Hemingway, 1927, p. 41): Out of the window of the hospital you could see a field with tumbleweed coming out of the snow, and a bare clay butte.... From the other window, if the bed was turned, you could see the

Much indirect evidence supports the hypothesis that transformations of mental images are

Work in philosophy and psychology has argued for a dissociation between perceptuallybased similarity and higher-level rules in conceptual thought. Although such a dissociation may be justified at times, our goal is to illustrate ways in which conceptual processing is grounded in perception, both for perceptual similarity and abstract rules. We discuss the advantages, power and influences of perceptually-based representations. First, many of the properties associated with amodal symbol systems can be achieved with perceptually-based systems as well (e.g. productivity). Second, relatively raw perceptual representations are powerful because they can implicitly represent properties in an analog fashion. Third, perception naturally provides impressions of overall similarity, exactly the type of similarity useful for establishing many common categories. Fourth, perceptual similarity is not static but becomes tuned over time to conceptual demands. Fifth, the original motivation or basis for sophisticated cognition is often less sophisticated perceptual similarity. Sixth, perceptual simulation occurs even in conceptual tasks that have no explicit perceptual demands. Parallels between perceptual and conceptual processes suggest that many mechanisms typically associated

This article pursues the possibility that perceivers are sensitive to implicit dynamic information even when they are not able to observe real-time change. Recent empirical results in the domains of handwriting recognition and picture perception are discussed in support of the hypothesis that perception involves acquiring information about transitions, whether the stimuli are static or dynamic. It is then argued that dynamic information has a special status in mental representation as well as in perception. In particular I propose that some mental representations may be dynamic, in that a temporal dimension is necessary to the representation. Recent evidence that mental representations may exhibit a form of momentum is discussed in support of this claim. There has been a growing appreciation of the impressive ability that the human mind has for perceiving events that take place over time. J. J. Gibson (1979), Johansson (1975), and others have noted that we are particularly receptive to information contained in patterns of change in the environment, as opposed to static information (such as that contained in a snapshot). In this article I will first propose that people perceive dynamic information even when the stimuli being inspected (such as snapshots) are not changing in real time. I will then propose that the importance of dynamic information to perception has implications for mental representation. In particular I will argue that mental representations may sometimes contain a temporal dimension and may thus themselves he dynamic. Perceiving Transitions I pr~ose that in oerception, acquiring information about transitions between states is as important as acquiring information about the states themselves. I believe that the proclivity oeople show for picking up transitional information extends to situations in which the stimuli are static. A more precise proposition can be stated as follows: When the perceptual system cannot directly perceive change over time it will seek out implicit Sections of this article are based on portions of a dissertation I submitted

Theories of visual object recognition must solve the problem of recognizing 3D objects given that perceivers only receive 2D patterns of light on their retinae. Recent findings from human psychophysics, neurophysiology and machine vision provide converging evidence for `image-based' models in which objects are represented as collections of viewpoint-specific local features. This approach is contrasted with `structural-description' models in which objects are represented as configurations of 3D volumes or parts. We then review recent behavioral results that address the biological plausibility of both approaches, as well as some of their computational advantages and limitations. We conclude that, although the image-based approach holds great promise, it has potential pitfalls that may be best overcome by including structural information. Thus, the most viable model of object recognition may be one that incorporates the most appealing aspects of both image-based and structural-description theories. 1998 Elsevier Science B.V. All rights reserved Keywords: Object recognition; Image-based model; Structural description 1.

We present a study of complex visualization usage by expert meteorological forecasters. We performed a protocol analysis and examined the types of visualizations they examined. We present evidence for how experts are able to make use of complex visualizations. Our #ndings suggest that users of complex visualizations create qualitativemental models from which they can then generate quantitative information. In order to build their qualitative mental models, forecasters integrated information across multiple visualizations and extracted primarily qualitative information from visualizations in a goal-directed manner. We discuss both theoretical and practical implications of this study. Introduction Everywhere you look, newspapers and banners declare this the #Information Age." Scientists, engineers, and weather forecasters #just to name a few# examine extremely large amounts of data on a daily basis. The visualizations that they examine have so much data that it is obvious that...