12 research outputs found

    The beholder’s share in the perception of orientation of 2D shapes.

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    Previous research on orientation perception of twodimensional (2-D) shapes has demonstrated a higher performance at cardinal orientations (horizontal and vertical) than at oblique orientations. This superiority of performance around the vertical and the horizontal is called the oblique effect (see the reviews of The oblique effect results in higher accuracy and precision in the ability to match and discriminate orientations around the vertical and the horizontal than in other orientations, and many empirical results show this effect. Andrews (1967) presented a short line at the fovea and asked observers to set it parallel to a long reference line. The results showed the oblique effect both in accuracy and in precision. Bouma and Andriessen (1968) asked observers to set a point on the extension of a line segment and obtained similar results; the point setting was more accurate and precise for cardinal orientations than for oblique ones. Westheimer and Beard (1998) used an orientation discrimination task to investigate the orientation perception of lines. Observers were shown a line at a specific orientation, followed by another line at another orientation, and they were asked whether the second one was clockwise or counterclockwise relative to the orientation of the f irst line. Results of this orientation discrimination task again showed the oblique effect. There is much discussion about the origin of the oblique effect. Two types of explanations have been put forward: those based on properties of neural processing (see 1227 Copyright 2002 Psychonomic Society, Inc. This work was supported by National Science Foundation Grant SBR-9809447 and by a seed grant from The Ohio State University. We thank Manoj Subbaram and Mark A. Bullimore of the College of Optometry at OSU for testing our observers for astigmatism. We thank Jim Crowell, Jim Todd, and two anonymous reviewers for helpful suggestions. Correspondence concerning this article should be addressed to B. Liu, School of Optometry, University of California, 360 Minor Hall, Berkeley, CA 94720 (e-mail: [email protected]). A considerable amount of research demonstrates that people perceive cardinal orientations (horizontal and vertical) more accurately than other orientations; this is termed the oblique effect. We investigated the interaction of this effect with the degree of elongation of the stimulus. Our stimuli were ellipses with a wide range of aspect ratios, varying from a circle (aspect ratio = 1) to a line (aspect ratio = 123.5). The task was to set a probe line in the same orientation as the long axis of the ellipse. In our first experiment, we determined that performance is degraded as the aspect ratio decreases; furthermore, the bias and response variability are linearly related to a transformation of aspect ratio (roundness). We found significant individual differences; the results show high within-subjects correlations and low between-subjects correlations. In our second experiment, we had observers judge the orientation of circles randomly mixed in with ellipses of low aspect ratio. The observers demonstrated intrinsic preferences and generated reproducible distributions of orientation settings with idiosyncratic profiles. These distributions predict the influence on the response to ellipses with an aspect ratio higher than one and can be considered as the beholder's share in the perception of shape orientation

    Coordinating (Shared) Perspectives in Robot Assisted Search & Rescue.

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    ABSTRACT From high fidelity field exercises to disaster response deployments, search and rescue robots are being readily integrated into rescue operations. Previous research has proposed that for such new technology to be successful in an operation the organization architecture needs to support the coordination of shared perspectives between the human team members and the robotic platforms. For this, the robot platforms need to be effective team players in the field of practice. Based on this conceptual model, this paper introduces a novel software interface utilizing virtual position and orientation indicators to alleviate perceptual ambiguities and navigation problems experienced by robot handlers and problem holders. By actively orchestrating and sharing these indicators between handler and operator displays, the interface caters to user expertise and to the natural competency of the human perceptual system. These probes provide a basic tool for aiding robot navigation and way-finding fundamental to effective team coordination and communication in urban search and rescue missions

    Research Article The Perception of Doubly Curved Surfaces From Anisotropic Textures

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    ABSTRACT—Most existing computational models of the visual perception of three-dimensional shape from texture are based on assumed constraints about how texture is distributed on visible surfaces. The research described in the present article was designed to investigate how violations of these assumptions influence human perception. Observers were presented with images of smoothly curved surfaces depicted with different types of texture, whose distribution of surface markings could be both anisotropic and inhomogeneous. Observers judged the pattern of ordinal depth on each object by marking local maxima and minima along designated scan lines. They also judged the apparent magnitudes of relative depth between designated probe points on the surface. The results revealed a high degree of accuracy and reliability in all conditions, except for a systematic underestimation of the overall magnitude of surface relief

    On the affine structure of perceptual space

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    Affine geometry is a generalization of Euclidean geometry in which distance can be scaled along parallel directions, though relative distances in different directions men be incommensurable. This article presents a new procedure for testing the intrinsic affine structure of a psychological space by having subjects perform bisection judgments over multiple directions. If those judgments are internally consistent with one another, they must satisfy a theorem first proved by Pierre Varignon around 300 years ago. In the experiment reported here, this procedure was employed to measure the perceived structure of a visual ground surface. The results revealed that observers' judgments were systematically distorted relative to the physical environment, but that the judged bisections in different directions had an internally consistent affine structure. Implications of these findings for other possible response tasks are considered

    The Perception of Doubly Curved Surfaces from Anisotropic Textures

    No full text
    Most existing computational models of the visual perception of three-dimensional shape from texture are based on assumed constraints about how texture is distributed on visible surfaces. The research described in the present article was designed to investigate how violations of these assumptions influence human perception. Observers were presented with images of smoothly curved surfaces depicted with different types of texture, whose distribution of surface markings could be both anisotropic and inhomogeneous. Observers judged the pattern of ordinal depth on each object by marking local maxima and minima along designated scan lines. They also judged the apparent magnitudes of relative depth between designated probe points on the surface. The results revealed a high degree of accuracy and reliability in all conditions, except for a systematic underestimation of the overall magnitude of surface relief. These findings suggest that human perception of three-dimensional shape from texture is much more robust than would be reasonable to expect based on current computational models of this phenomenon
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