Many researchers have proposed that, for the purpose of recognition, human vision parses shapes into component parts. Precisely how is not yet known. The minima rule for silhouettes (Hoffman & Richards, 1984) defines boundary points at which to parse but does not tell how to use these points to cut silhouettes and, therefore, does not tell what the parts are. In this paper, we propose the short-cut rule, which states that, other things being equal, human vision prefers to use the shortest possible cuts to parse silhouettes. We motivate this rule, and the well-known Petter's rule for modal completion, by the principle of transversality. We present five psychophysical experiments that test the short-cut rule, show that it successfully predicts part cuts that connect boundary points given by the minima rule, and show that it can also create new boundary points.

The present study was designed to compare the subjective complaints of 50 traumatically brain injured (TBI) patients with the observations of their significant others. The complaints of the TBI patients and their significant others were contrasted according to the severity of the TBI and the type of complaint (physical, cognitive/behavioural and emotional). While no differences were found in physical complaints, the cognitive/behavioural and emotional complaints of TBI patients, regardless of the severity of the initial TBI, were significantly under-reported in comparison to the observations of their significant others. The data suggests that while this finding was most likely due to the TBI patients' poor awareness, it was unlikely to be the result of psychological denial since all of these individuals were evaluated in the context of being a plaintiff in personal injury litigation or a claimant in a Workers' Compensation claim. The data suggests that the cerebral trauma these patients sustained played a major role in their ability to recognize their cognitive, behavioural and emotional symptoms. Finally, the data suggests that clinicians should obtain information about the TBI patients' cognitive/behavioural and emotional functioning from their significant others, rather than rely entirely on the TBI patients' subjective assessment of these problems.

We describe methods for displaying complex, texturemapped environments with four or more spatial dimensions that allow for real-time interaction. At any one moment in time, a three-dimensional cross section of the high-dimensional environment is rendered using techniques that have been implemented in OpenGL. The position and orientation of the user within the environment determine the 3-D cross section. A variety of interfaces can be used to control position and orientation in 4-D, including a mouse “freelook” interface for use with a computer monitor display, and an interface that uses a head-tracking system with three degrees of freedom and PINCH gloves in combination with a head-mounted display. The methods avoid the use of projections that require depth buffering in greater than three dimensions and can be used in conjunction with either 2-D or 3-D texture mapping. A computer graphic engine that displays 4-D virtual environments interactively uses these methods, as does a level editor and modeling program that can be used to create 4-D environments.

Cognitive and neurobehavioral symptoms are common following traumatic brain injuries (TBIs). Because malingerers are likely to complain of such symptoms and perform poorly on neuropsychological tests, clinicians may have considerable difficulty distinguishing malingerers from TBI patients. In this study, we compared the subjective complaints of malingerers to TBI patients and then compared both groups to the problems observed by their respective significant others. We tested the assumption whether significant others could add one more piece to the challenging puzzle of diagnosing malingering. Our results demonstrated that the malingerers complained of more problems than patients who had sustained moderate or severe TBI. However, the significant others of the malingerers observed fewer cognitive, emotional-behavioral, and total problems than did the significant others of patients with severe, moderate, and even mild TBI. These findings suggest that the detection of malingering can be enhanced by interviews with significant others.

Methods for representing spacetime events as hyperobjects in four-dimensional (4D) space have been developed that let one examine events from arbitrary spacetime perspectives. Three-dimensional (3D) objects that move either rigidly or nonrigidly are extruded to create 4D hyperobjects. The boundaries of the 4D objects are represented using polyhedra, in much the same way that the boundaries of 3D objects may be represented using polygons. The user views one or more static, 4D hyperobjects using software which lets the user control in an interactive, realtime fashion the position and orientation of a 3D cross-section of the hyperobjects. The 3D cross-sections are rendered using standard techniques of 3D computer graphics. Extrusion of nonrigid 3D objects is useful for visualizing events that involve objects with time-varying shape. For instance, one can use nonrigid extrusion to visualize a character animation, in which multiple frames of a walking humanoid character are used to create a single, static hyperobject that represents the entire animation. With these methods, one need no longer be limited to watching a movie in which time is a hidden axis. Rather, one can view and alter events immersively from arbitrary vantage points.