Barry L. Richardson

The Ecological and Construct Validity of a Newly Developed Measure of Executive Function: The Virtual Library Task

Virtual reality (VR) assessment paradigms have the potential to address the limited ecological validity of pen and paper measures of executive function (EF) and the pragmatic and reliability issues associated with functional measures. To investigate the ecological validity and construct validity of a newly developed VR measure of EF, the Virtual Library Task (VLT); a real life analogous task--the Real Library Task (RLT); and five neuropsychological measures of EF were administered to 30 patients with traumatic brain injury (TBI) and 30 healthy Controls. Significant others for each participant also completed the Dysexecutive Questionnaire (DEX), which is a behavioral rating scale of everyday EF. Performances on the VLT and the RLT were significantly positively correlated indicating that VR performance is similar to real world performance. The TBI group performed significantly worse than the Control group on the VLT and the Modified Six Elements Test (MSET) but the other four neuropsychological measures of EF failed to differentiate the groups. Both the MSET and the VLT significantly predicted everyday EF suggesting that they are both ecologically valid tools for the assessment of EF. The VLT has the advantage over the MSET of providing objective measurement of individual components of EF.

Physics-Based Haptic Simulation of Bone Machining

We present a physics-based training simulator for bone machining. Based on experimental studies, the energy required to remove a unit volume of bone is a constant for every particular bone material. We use this physical principle to obtain the forces required to remove bone material with a milling tool rotating at high speed. The rotating blades of the tool are modeled as a set of small cutting elements. The force of interaction between a cutting element and bone is calculated from the energy required to remove a bone chip with an estimated thickness and known material stiffness. The total force acting on the cutter at a particular instant is obtained by integrating the differential forces over all cutting elements engaged. A voxel representation is used to represent the virtual bone and removed chips for calculating forces of machining. We use voxels that carry bone material properties to represent the volumetric haptic body and to apply underlying physical changes during machining. Experimental results of machining samples of a real bone confirm the force model. A real-time haptic implementation of the method in a dental training simulator is described.

Raised line drawings are spontaneously explored with a single finger.

In this study we examine the strategies used by blindfolded subjects asked to freely explore raised line drawings and identify what is depicted in them. We were particularly interested in how often a single finger is spontaneously used because in several studies subjects are forced to use only one fingertip and the extent to which this restriction may depress haptic perception is unclear. The results suggest that despite a variety of strategies, people ‘naturally’ use single fingertips sufficiently often to allow confidence in conclusions that are based on studies imposing this restriction.

Components of Haptic Information: Skin Rivals Kinaesthesis

Four components of the haptic system were investigated, in isolation and in various combinations, during passive-guided exploration of raised-line drawings. The components were kinaesthesis, cutaneous input from the presence of a raised line, shear forces from relative movement between the skin and a textured surface, and attenuated distortions at the fingertip resulting from relative movement between the fingertip and a surface. Although the presence of kinaesthetic information was found to be positively correlated with performance in a task of identifying raised-line letters, conditions involving touch alone yielded performance equivalent to that when kinaesthesis was involved. Together, these results suggest that tactile information could be as effective as kinaesthetic information. The results are discussed in terms of applications to the design of human – machine interfaces.

A Tactile Sensor for Incipient Slip Detection

This article introduces a new tactile sensor for incipient slip detection. The sensor has concentric circular ridges over its surface and is designed with the aim of differentiating between local slip and total slip. Partial deformation of ridges on the edge of contact with the object exposes built-in fiber optics to ambient light. Changes in light signals are used as an indication of incipient slip. A two-stage computer simulation is presented using finite element, graphics, and image processing software. Experiments reveal an early change in light signals that can be used to ensure the effectiveness of the proposed Sensor.

Haptic and visual size judgements in virtual and real environments

In a series of three experiments, participants were asked to match the sizes of spheres presented in the haptic and visual modalities. Stimuli were either real or virtual. Real spheres were sets of ball bearings of various sizes that could be both viewed and touched. Virtual spheres were presented using a Phantom for the haptic presentations or a 4D screen for the visual presentations. Comparing the judgements made within sensory modalities, virtual spheres of a given size were perceived as significantly larger than their real counterparts for vision, but not for haptics. Across modalities, virtual haptic spheres were perceived as significantly larger than their virtual visual counterparts, while there was no significant difference in the judged size of real visual and real haptic spheres. The results have implications for the design of virtual environments where it cannot be assumed that the sizes of objects as depicted by their designers will be perceived in identical fashion across modalities.

Intrasensory attention: kinaesthetic versus cutaneous inputs.

Blindfolded participants felt pairs of raised-line drawings simultaneously, one with each index finger. The stimuli presented at each fingertip were 180° rotations of each other (eg 6 and 9). One finger moved (either actively or passively), and this in turn caused movement of a matched raised line underneath the stationary finger on the other hand, in a yoked manner. Thus, a 6 at the moving finger would be felt as a 9 on the stationary finger. On all trials there was a raised line moving underneath the stationary fully passive finger. For the moving finger, a raised line was present on only half of the trials. When a raised line could be felt at the moving fingertip, the shape followed by this finger was more often reported than was the shape present at the other (stationary) fingertip. However, when no line was present under the moving finger (ie when movement became the major cue for shape), subjects reported experiencing the shape moved under the stationary fingertip. Results are interpreted as an indication that cutaneous information can be more ‘attention-getting’ than kinaesthetic information, and are considered to support the modality-appropriateness theory.

Visual and haptic influence on perception of stimulus size

In six experiments, subjects judged the sizes of squares that were presented visually and/or haptically, in unimodal or bimodal conditions. We were interested in which mode most affected size judgments in the bimodal condition when the squares presented to each mode actually differed in size. Three factors varied: whether haptic exploration was passive or active, whether the choice set from which the subjects selected their responses was visual or haptic, and whether cutaneous information was provided in addition to kinesthetic information. To match the task for each mode, visual presentations consisted of a cursor that moved along a square pathway to correspond to the haptic experience of successive segments revealed during exploration. We found that the visual influence on size judgments was greater than the influence of haptics when the haptic experience involved only kinesthesis, passive movement, and a visual choice set. However, when cutaneous input was added to kinesthetic information, size judgments were most influenced by the haptic mode. The results support hypotheses of sensory integration, rather than capture of one sense by the other.

Modification of Magnitude Estimations in Thermotactile Perception during Self-Generated and Externally Generated Movements

Fourteen participants felt a ‘cold’ stimulus move across a fingertip. When movement was self-controlled, the stimulus was reported as feeling less ‘cold’ than when movement was externally generated.

The contribution of virtual reality to research on sensory feedback in remote control

Here we consider research on the kinds of sensory information most effective as feedback during remote control of machines, and the role of virtual reality and telepresence in that research. We argue that full automation is a distant goal and that remote control deserves continued attention and improvement. Visual feedback to controllers has developed in various ways but autostereoscopic displays have yet to be proven. Haptic force feedback, in both real and virtual settings, has been demonstrated to offer much to the remote control environment and has led to a greater understanding of the kinesthetic and cutaneous components of haptics, and their role in multimodal processes, such as sensory capture and integration. We suggest that many displays using primarily visual feedback would benefit from the addition of haptic information but that much is yet to be learned about optimizing such displays.