The results of two types of experiments are reported. In 1 type, Ss matched depth intervals on the ground plane that appeared equal to frontal intervals at the same distance. The depth intervals had to be made considerably larger than the frontal intervals to appear equal in length, with this physical inequality of equal-appearing intervals increasing with egocentric distance of the intervals (4 m-12 m). In the other type of experiment, Ss viewed targets lying on the ground plane and then, with eyes closed, attempted either to walk directly to their locations or to point continuously toward them while walking along paths that passed off to the side. Performance was quite accurate in both motoric tasks, indicating that the distortion in the mapping from physical to visual space evident in the visual matching task does not manifest itself in the visually open-loop motoric tasks.

Haptic identification of real objects is superior to that of raised two-dimensional (2-D) depictions. Three explanations of real-object superiority were investigated: contribution of material information, contribution of 3-D shape and size, and greater potential for integration across the fingers. In Experiment 1, subjects, while wearing gloves that gently attenuated material information, haptically identified real objects that provided reduced cues to compliance, mass, and part motion. The gloves permitted exploration with free hand movement, a single outstretched finger, or five outstretched fingers. Performance decreased over these three conditions but was superior to identification of pictures of the same objects in all cases, indicating the contribution of 3-D structure and integration across the fingers. Picture performance was also better with five fingers than with one. In Experiment 2, the subjects wore open-fingered gloves, which provided them with material information. Consequently, the effect of type of exploration was substantially reduced but not eliminated. Material compensates somewhat for limited access to object structure but is not the primary basis for haptic object identification.It has been amply demonstrated that people's ability to identify raised line drawings of common objects, using touch alone, is quite poor (Ikeda & Uchikawa, 1978;Kennedy & Fox, 1977;Lederman, Klatzky, Chataway, & Summers, 1990;Loomis, Klatzky, & Lederman, 1991;Magee & Kennedy, 1980). Subjects may spend several minutes on a single picture, and accuracy is generally below 50%-sometimes well below. This is especially striking when one considers that haptic identification of real, common objects is both fast and accurate, with modal response latency observed to be under 2 sec and accuracy near 100% (Klatzky, Lederman, & Metzger, 1985). The purpose of the present study is to evaluate potential explanations of these differences in performance with real objects and two-dimensional (2-D) depictions. We consider three explanations, which are not meant to be mutually exclusive.The first account of picture/object differences focuses on a salient aspect of haptic perception-namely, that the Copyright 1993 Psychonomic Society, Inc."field of view" provided by the fingertip is quite restricted relative to vision. According to this account, objects provide a greater functional field of view than do pictures. A study of haptic picture identification by Loomis et al. (1991) indicated that performance was critically limited by field of view. Earlier studies by Becker (1935) and Yamane (1935) had displayed a visual pattern behind a small aperture, showing a similarity between vision and touch under these conditions. Loomis et al. 's more recent experiment attempted to equate the effective field of view for haptics and vision by constraining visual exposure to an aperture that was equivalent to the exploring fingerpad(s). In thehaptic conditions, subjects explored raiseddrawings with either the index finger or the contiguous index and...

Processes involved in sensing, representing, and recognizing environmental information and using that information to navigate have been the long-standing interest in cognitive psychology and geography (for example, Golledge 1992). An understanding of these abilities is critical to the effective design of systems intended to aid navigation, such as Geographic Information Systems, electronic maps, or hand-held GPS systems (in the nascent stage for personal navigation).The same understanding is sought by today's architects and urban planners, who are sensitive to the fact that people's navigation behavior is mediated by their mental models of physical environments (Passini 1984).Two general concerns in the navigation literature are how features of the environment are used to plan routes and guide ongoing navigation and how the act Naofumi Fujita is with the faculty of education, Kochi University, Japan. Roberta L Klatzky and Jack M. Loomis are professors of psychology, University of Calijhrnia, Santu Barbara. Reginald G. Colledge is professor of geography, University of Calijbwzia, Santu Barbara.

A number of organisms are capable of traveling directly back to the origin of locomotion afer following a circuitous outbound path, using dead-reckoning navigation. We describe a minimal representation that could be used for such navigation. It involves keeping track of only the polar coordinates of the origin of locomotion with respect to the observer's current location. An exact solution is provided first, followed by a simplij?ed solution, then a solution involving linearization of trigonometric functions. The paper also examines pegormance attainable with these solutions and briefly considers ways in which the model might be modij?ed to account fbr human navigation without reference to landmarks.The present paper concerns what is called path integration or dead-reckoning navigation. By this process, the navigator attempts to keep track of his/her position in some coordinate system solely on the basis of information about self-motion (Mittelstaedt and Mittelstaedt 1982); no reference is made to external cues. In contrast, most navigation by humans and nonhuman species depends on the sensing of external signals about position and orientation (Able ). These signals derive from the earth's magnetic field, wind, ocean currents, celestial bodies, and landmarks on the earth's surface.As both near and far space is further explored, and as more complex systems for observing the earth from space come into existence, ever more sophisticated navigational aids are being developed. Examples include global positioning systems (GPS) and geographic information systems (GIS) (Kunzig 1988). Navigational

The purpose of this study was to investigate whether the individuals in the general population with high scores on the Autism Spectrum Quotient constituted a single homogeneous group or not. A cohort of university students (n = 4901) was investigated by cluster analysis based on the original five subscales of the Autism Spectrum Quotient. Based on the results of the analysis, the students could be divided into six clusters: the first with low scores on all the five subscales, the second with high scores on only the 'attention to detail' subscale, the third and fourth with intermediate scores on all the subscales, the fifth with high scores on four of the five subscales but low scores on the 'attention to detail' subscale and the sixth with high scores on all the five subscales. The students with high total Autism Spectrum Quotient scores (n = 166) were divided into two groups: one with high scores on four subscales but low scores on the 'attention to detail' subscale and the other with high scores on all the five subscales. The results of this study suggested that individuals from the general population with high Autism Spectrum Quotient scores may consist of two qualitatively different groups.