Knowledge argument

The knowledge argument is an argument against physicalism, the view that the world is wholly physical. It was developed by Frank Jackson (1943–) and is based on the following thought experiment. Everything that can be known through the physical, chemical, and biological sciences – the complete physical truth – has been discovered. Mary is a brilliant scientist who is raised in a black-and-white room. She has never had colour experiences. But she learns the complete physical truth, which includes the completed science of colour vision, by reading books and watching lectures on a black-and-white television monitor. Then she leaves the room and sees colours. Jackson’s argument runs roughly as follows. When Mary leaves the room, she learns something new. She learns what it is like to see in colour. Evidently, the complete physical truth is not the complete truth about the world. Ergo, physicalism is false. Some react by denying that Mary learns anything when she leaves the room. Others react by accepting that she learns something but denying that this refutes physicalism. Still others accept the argument as sound. The ensuing discussion has led to a variety of insights about consciousness and its place in the natural world.

Work-related Musculoskeletal Disorders in Sonography and the Alexander Technique

Work-related musculoskeletal disorder (WRMSD) is a problem affecting growing numbers of sonographers. The condition often leads to considerable pain for the individuals concerned and inconvenience for departments struggling to cope with increasing workloads. Employers and equipment manufacturers are making efforts to address the problem, but the number of cases of WRMSD continues to increase. This study looks at a different approach to tackling the problem, introducing student sonographers to a technique often used in other professions to overcome stress and damage to the body caused by repetitive movements. The 'Alexander technique' (AT) is a method of increasing an individual's awareness of their body and mind when performing an activity. In a profession such as sonography, where the practitioner is concentrating for long periods of time on interpreting images on a television monitor, the position and movement of the body is usually ignored. By working with a skilled teacher, individuals can be shown how to work more effectively, leading to a possible reduction in stress to the body. Initial results indicate that AT has potential to be of benefit to sonographers in preventing or reducing the incidence of WRMSD; further work is planned.

Personal Information in Searching for Faces

Participants searched for a target on a television monitor either after they viewed pictures and received physical information about the target or received that information augmented by personal information. Based on a levels of processing perspective we predicted that the addition of personal information would stimulate deeper processing and result in better identification performance. Personal information did increase identification accuracy, as anticipated. Personal information also increased the duration of time spent on the search task relative to a distractor task, suggesting that personal information may have done more than deepen the processing at the time of encoding. In the current climate of terrorism, this increase in identification performance via a surveillance camera has clear applied significance.

Technology Tips: January 2000

Such presentation software as Microsoft Power-Point can be used to review content in many areas of mathematics. I recently created a slide-show presentation called “math Jeopardy” as a chapterreview activity for my students. I used a mobile computer connected to a large-screen television monitor to display the presentation in front of the classroom.

Relative Influence of Sensory Cues in a Multi-Modal Virtual Environment

Human subject experiments were performed to determine the influence of multimodal virtual environment display parameters on the perception of haptic, visual, and aural material properties. Twelve subjects participated in two experiments. Subjects were presented with a test material (real or virtual) and were asked to select one of three reference materials which most closely matched the test material. Subject were also asked to rate the quality of the match on a 1–5 scale. The test and reference materials were presented to subjects through a television monitor. The visual characteristics of the virtual materials were generated on a graphics display, the haptic characteristics were displayed using a single degree of freedom haptic device, and the aural characteristics were created using prerecorded sound clips. The results of the two experiments suggest that haptic characteristics played an important role in the matching process while sound and visual characteristics played an important role in the quality rating process.

Stereoscopic Transparency and Segregation in Depth

We previously described the spatiotemporal requirements for binocular correlation in stereopsis using sinusoidal gratings-in-depth (Lankheet and Lennie, 1996 Vision Research36 527 – 538). The use of smooth sinusoidal surfaces emphasised the effects of spatial and temporal integration. Binocular correlation, however, depends not only on integration, but also on segregation at depth discontinuities. In the present experiments we therefore investigated segregation-in-depth, using random dot stereograms that depicted two transparent frontoparallel planes positioned symmetrically on either side of a binocular fixation point. Sensitivity for segregating the two planes was established by adding Gaussian distributed disparity noise to the disparities specifying the planes, and finding the noise amplitude that rendered transparency just detectable. The stimuli consisted of dynamic random-dot displays (dot lifetime 4 frames, at a frame rate of 67 Hz), generated in real time by a Macintosh computer, displayed on a television monitor, and viewed through a stereoscope. We used a method of constant stimuli and a 2AFC procedure. Two transparent planes were presented in one interval, and a single plane, with Gaussian distributed disparity values spanning the same range, was presented in the other. Segregation of stationary patterns was optimal for disparity differences of about ±9 min arc. Differences smaller than ±3 min arc and larger than about ±18 min arc could not be resolved. Motion contrast between the two patterns greatly facilitated segregation in depth. The facilitating effect increased with the difference in motion directions. The optimal speed varied with the difference in disparity.