Some aspects of navigation performance can be improved primarily by using the optimal map configuration; other aspects require using the optimal configuration and having better spatial ability.

Previous research has identified a variety of strategies used by novice and experienced navigators in making cardinal direction judgments (Gugerty, Brooks, & Treadaway, 2004). We developed an ACT-R cognitive model of some of these strategies that instantiated a number of concepts from research in spatial cognition, including a visual-short-term-memory buffer overlaid on a perceptual buffer, an egocentric reference frame in visual-short-term-memory, storage of categorical spatial information in visual-short-term-memory, and rotation of a mental compass in visual-short-termmemory. Response times predicted by the model fit well with the data of two groups, college students (N D 20) trained and practiced in the modeled strategies, and jet pilots (N D 4) with no strategy training. Thus, the cognitive model seems to provide an accurate description of important strategies for cardinal direction judgments. Additionally, it demonstrates how theoretical constructs in spatial cognition can be applied to a complex, realistic navigation task.

Recent studies have shown that great ape species possess patterns of macrostructural neocortical asymmetries that are similar to those found in humans. However, little is known about the asymmetry of subcortical structures in great apes. To address this lack of data, the authors assessed left-right asymmetry of the anterior and posterior aspects of cerebellum from MRI brain scans of 53 chimpanzees (Pan troglodytes). No population-level bias was found for either the anterior or the posterior region of the cerebellum. However, a significant inverse association was found in the asymmetry quotients of the anterior and posterior regions, indicating that the cerebellum was torqued at the individual level. Additionally, handedness for tool use but not other measures was associated with variation in cerebellar asymmetries. Last, older chimpanzees had a smaller cerebellum after brain volume was adjusted for. The results are discussed in the context of brain changes in primate evolution related to tool use. Keywordscerebellum; torque; tool use; handedness; chimpanzee Over the last 5 years, an increasing body of evidence has shown the presence of macrostructural asymmetries in the great ape brain that closely resemble well-known patterns of asymmetry in the human brain Pilcher, Hammock, & Hopkins, 2001). Most of these studies have focused on the neocortex, particularly on regions believed to be homologous to cortical areas of the human brain involved in linguistic functions. For example, in great apes, as in humans, the sylvian fissure has been reported to be longer in the left hemisphere, particularly in its postcentral region Hopkins, Pilcher, & MacGregor, 2000;Yeni-Komshian & Benson, 1976). Similarly, leftward cortical asymmetries in great apes and humans have been reported for the planum temporale, an area located on the superior temporal gyrus, which coincides with part of Wernicke's area Correspondence concerning this article should be addressed to Claudio Cantalupo, Department of Psychology, Clemson University, Clemson, SC 29634. E-mail: ccantal@clemson.edu. Galaburda, 1995;Gannon, Holloway, Broadfield, & Braun, 1998;Gilissen, 2001;Hopkins, Marino, Rilling, & MacGregor, 1998). A number of studies have also reported leftward asymmetries in the frontal operculum in the inferior frontal lobe, commonly believed to contain part of Broca's area (Amunts et al., 1999;Cantalupo & Hopkins, 2001;Foundas, Eure, Luevano, & Weinberger, 1998), although the scope of this finding remains to be fully assessed (Sherwood, Broadfield, Holloway, Gannon, & Hof, 2003;Watkins et al., 2001). Some studies have revealed converging asymmetry patterns also in other regions of the great ape and human brain. For example, the great ape brain has been found to show the same frontal (right > left) and occipital (left > right) petalias, also known as developmental torque, consistently reported in the human literature (Holloway & De La Coste-Lareymondie, 1982;Hopkins & Marino, 2000;LeMay, 1976LeMay, , 1982LeMay, , 1985Pilcher et al., 2001). Fi...

The results of two usability experiments evaluating an interface for the operation of OctArm, a biologically inspired robotic arm modeled after an octopus tentacle, are reported. Due to the many degrees-of-freedom (DOF) for the operator to control, such "continuum" robotic limbs provide unique challenges for human operators because they do not map intuitively. Two modes have been developed to control the arm and reduce the DOF under the explicit direction of the operator. In coupled velocity (CV) mode, a joystick controls changes in arm curvature. In end-effector (EE) mode, a joystick controls the arm by moving the position of an endpoint along a straight line. In Experiment 1, participants used the two modes to grasp objects placed at different locations in a virtual reality modeling language (VRML). Objective measures of performance and subjective preferences were recorded. Results revealed lower grasp times and a subjective preference for the CV mode. Recommendations for improving the interface included providing additional feedback and implementation of an error recovery function. In Experiment 2, only the CV mode was tested with improved training of participants and several changes to the interface. The error recovery function was implemented, allowing participants to reverse through previously attained positions. The mean time to complete the trials in the second usability test was reduced by more than 4 minutes compared with the first usability test, confirming the interface changes improved performance. The results of these tests will be incorporated into future versions of the arm and improve future usability tests.