We report results from a formal user study of interactive 3D rotation using the mouse-driven Virtual Sphere and Arcball techniques, as well as multidimensional input techniques based on magnetic orientation sensors. MultidimensionaI input is often assumed to allow users to work quickly, but at the cost of precision, due to the instability of the hand moving in the open air. We show that, at least for the orientation matching task used in this experiment, users can take advantage of the integrated degrees of freedom provided by multidimensional input without necessarily sacrificing precision: using multidimensional input, users completed the experimental task up to 36% faster without any statistically detectable loss of accuracy. We also report detailed observations of common usability problems when first encountering the techniques. Our observations suggest some design issues for 3D input devices. For example, the physical form-factors of the 3D input device significantly influenced user acceptance of otherwise identical input sensors. The device should afford some tactile cues, so the user can feel its orientation without looking at it. In the absence of such cues, some test users were unsure of how to use the device. 

We present an experiment on cooperative bimanual action. Right-handed subjects manipulated a pair of physical objects, a tool and a target object, so that the tool would touch a target on the object @g. 1). For this task, there is a marked specialization of the hands. Performance is best when the left hand orients the target object and the right hand manipulates the tool, but is significantly reduced when these roles are reversed. This suggests that the right hand operates relative to the frame-of-reference of the left hand. Furthermore, when physical constraints guide the tool placement, this fundamentally changes the type of motor control required. The task is tremendously simplified for both hands, and reversing roles of the hands is no longer an important factor. Thus, specialization of the roles of the hands is significant only for skilled manipulation.

The influence of color as a surface feature versus its influence as stored knowledge in object recognition was assessed. Participants decided whether a briefly presented and masked picture matched a test name. For pictures and words referring to similarly shaped objects, semantic color similarity (SCS) was present when picture and word shared the same prototypical color (e.g., purple apple followed by cherry). Perceptual color similarity (PCS) was present when the surface color of the picture matched the prototypical color of the named object (e.g., purple apple followed by blueberry). Response interference was primarily due to SCS, despite the fact that participants based similarity ratings on PCS. When uncolored objects were used, SCS interference still occurred, implying that the influence of SCS did not depend on the presence of surface color. The results indicate that, relative to surface color, stored color knowledge was more influential in object recognition.

When shown a tilted container, people often fail to appreciate that the surface of the liquid contained within should remain horizontal with respect to the ground This study investigated how amenable this bias is to experience in relevant everyday situations Surprisingly, liquid surfaces that waitresses and bartenders considered natural deviated even more from horizontal than was the case for comparison groups This finding is, to our knowledge, the only documented case in which performance declines with experience We suggest that practical experience promotes a functionally relative perspective, in which the orientation of the liquid's surface is evaluated relative to that of its container as opposed to being related directly to the surrounding environment The container-relative perspective, in turn, evokes a perceptual bias that is responsible for the systematic errors observed on this task.

The accuracy of depth judgments that are based on binocular disparity or structure from motion (motion parallax and object rotation) was studied in 3 experiments. In Experiment 1, depth judgments were recorded for computer simulations of cones specified by binocular disparity, motion parallax, or stereokinesis. In Experiment 2, judgments were recorded for real cones in a structured environment, with depth information from binocular disparity, motion parallax, or object rotation about the y-axis. In both of these experiments, judgments from binocular disparity information were quite accurate, but judgments on the basis of geometrically equivalent or more robust motion information reflected poor recovery of quantitative depth information. A 3rd experiment demonstrated stereoscopic depth constancy for distances of 1 to 3 m using real objects in a well-illuminated, structured viewing environment in which monocular depth cues (e.g., shading) were minimized.

People judged the inclination of hills viewed either out-of-doors or in a computer-simulated virtual environment. Angle judgments were obtained by having people (1) provide verbal estimates, (2) adjust a representation of the hill’s cross-section, and (3) adjust a tilt board with their unseen hand. Geographical slant was greatly overestimated according to the first two measures, but not the third. Apparent slant judgments conformed to ratio scales, thereby enhancing sensitivity to the small inclines that must actually be traversed in everyday experience. It is proposed that the perceived exaggeration of geographical slant preserves the relationship between distal inclination and people’s behavioral potential. Hills are harder to traverse as people become tired; hence, apparent slant increased with fatigue. Visually guided actions must be accommodated to the actual distal properties of the environment; consequently, the tilt board adjustments did not reflect apparent slant overestimations, nor were they influenced by fatigue. Consistent with the fact that steep hills are more difficult to descend than to ascend, these hills appeared steeper when viewed from the top.