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Biomedical subjects

A J Courtney

Publications and source records attributed to A J Courtney.

At least 19 recordsLinked to original sources
PubMed2001

A study of the discriminability of shape symbols by the foot.

An experiment to test the discriminability of shape symbols using the shod foot was performed with 38 blind people (aged 23-72 years). Ten shape symbols which were 5 mm thick and fitted into a 30.5 cm2 tile were presented to subjects to identify by using only their feet. Each subject had 20 trials in which to discriminate the symbols. In each trial, a symbol was selected randomly and presented to the subject in randomized orientation. The subject was instructed to step on the symbol and to identify it using their own method. Time to discriminate a symbol and the accuracy of identification were recorded. A very high accuracy (93% on average) was obtained, which is comparable to the accuracy of tactile symbol discrimination using the hands. Average time to discriminate a symbol was 16 s with a standard deviation of 12.15 s, which indicated the high variability of the results. Owing to the high accuracy of identification, tactile foot-discriminable symbols have great potential as landmarks for blind people and if applied to a tactile guide path they could provide information for orientation and navigation.

Adult↗
PubMed2001

Safety and ergonomics evaluation of hybrid systems in Hong Kong.

This study is aimed at understanding common safety and ergonomics problems with robot installation in Hong Kong. Information was collected through direct observations and personal interviews with robot users from advanced hybrid manufacturing systems. The application areas of robots and types of safety devices employed were investigated. The ages, types of jobs, daily working hours and working conditions of personnel were examined. Fire precaution measures, types and varieties of training programs for users were analyzed. The results showed that although investments were made for installation of robots for improving production activity, limited attention was paid to the health, safety, and ergonomics aspects in the hybrid systems. There were also cases reported where no formal guidelines for robot manipulation and operation were provided. It seems that management and users paid attention to robot function and capability more than robot safety during robotization process. Conclusions were made by the authors that efforts should immediately be made to adopt recommendations on the safety devices and facilities and training requirements for improving users' health and safety before fatal accidents occur.

Accidents, Occupational↗
PubMed1998

Stimulus size scaling and foveal load as determinants of peripheral target detection.

This paper reports two experiments on the effect of scaling the size of stimuli (using factors derived from consideration of cortical magnification) on the detection of peripheral visual targets. In the first experiment two levels of magnification, fully M-scaled and half M-scaled, were used to scale stimuli that were presented briefly. The performance decrement normally associated with increasing retinal eccentricity did not occur with both levels of magnification. There was an unexpected decline in performance at low eccentricities and possible explanations are discussed. The second experiment investigated the effects of half M-scaling on a peripheral detection task with the addition of foveal cognitive loading as would be found in many practical tasks. Half M-scaling improved performance with and without the presence of foveal loading, and the improvement was greater for the foveal load condition when the target was at the larger eccentricities. These results provide a useful indication of the possibility of reducing the effect of tunnel vision for visual inspection tasks on visual displays or, possibly, control panels through the development of variable resolution projection displays matching the psychophysical properties of the human visual system.

Adult↗
PubMed1998

Revising and validating the random search model for competitive search.

A random search model was fit to a total of 2592 visual search times on a single-target detection task. By using a competing homogeneous background and uniform stimulus material, specifying viewing distance, controlling the presentation of search task material, and eliminating some options for extreme search strategies, very high correlation coefficients were found when a random search model was fit to both the individual data and to pooled data. A response time parameter was incorporated into the traditional random-search model and very good predictions of search performance were obtained.

Adolescent↗
PubMed1996

Visual search performance with complete and incomplete visual lobe areas.

A simulation study of the effects of visual lobe shape and search strategy on search performance is reported. Using a homogeneous pattern search task that did not dictate eye fixation movements (as in reading), three basic categories of strategy and two lobe shapes were tested. Random strategies with controlled overlap of lobe areas, representing various degrees of memory, were found to produce better performance (faster search times with equal or better detection rates) than either a completely random strategy or systematic strategies with various degrees of controlled visual lobe area overlap. The controlled overlap random strategies were far better able to compensate for non-optimum interfixation distances and distortion of visual lobe shape than systematic strategies.

Attention↗
PubMed1994

The effect of scale-side, indicator type, and control plane on direction-of-turn stereotypes for Hong Kong Chinese subjects.

This study investigates the influence of scale-side, pointer type, direction-of-increase, and control plane on direction-of-turn stereotypes for Chinese subjects using a variety of configurations of a linear display with a rotary control. Pointer type and direction of increase did not have a significant effect on direction-of-turn expectation. Strong stereotypes are found when Warrick's principle and the scale-side principle do not clash. In such a configuration, the scale is on the opposite side of the display to the control, and the display indicator moves in the same plane as the control. However, when the two principles clash, stereotypes are weakened or eliminated and no single principle dominates. For a rotary control placed to the right of a horizontal linear scale in the frontal plane there are strong clockwise-for-right and counterclockwise-for-left stereotypes which dominate the scale-side principle when there is a clash. The most marked stereotypes and fastest response times are obtained for the horizontal display with the control in the same frontal plane.

Adult↗
PubMed1994

Effects of priority assignment of attentional resources, order of testing, and response sequence on tunnel vision.

The effects of relative priority of attentional resources allocated to simultaneous peripheral and foveal tasks, response sequence to the tasks, and order to testing with two levels of foveal cognitive loading on tunnel vision were studied with 32 Chinese undergraduates. Two levels of foveal condition were used for the foveal task while the peripheral task required a single-target detection. Performance decrement value and a significant interaction of levels x eccentricities indicated that tunnel vision was most prominent when the foveal task was primary. Greater magnitude of tunnel vision was obtained when the more difficult foveal task was tested prior to the no-foveal-load condition. Responding sequence to the tasks was nonsignificant.

Adult↗
PubMed1993

Inter-relationships between visual lobe dimensions, search times and eye movement parameters for a competition search task.

The inter-relationships between visual lobe dimensions, search times and eye movement parameters were investigated for a competition search task with 18 subjects. The subjects had previously participated in a visual lobe measurement and two search performance experiments using the same set of stimulus material. Using an Eye Mark Recorder, the average search times of subjects were found to be comparatively longer than for previous search tasks not using the recorder, and relative search performance ranks of the subjects were altered. The method of stimulus presentation and the search area were different in this experiment, so we cannot be certain as to which factor or factors caused the lengthening of search times and changes in ranking. All subjects achieved a 100% hit rate with no mis-classification of targets. A very high correlation coefficient was obtained for cumulative detection percentage and pooled search times when fitted to a random search model. Average search times were found to be significantly correlated with fixation durations as well as with the number of fixations. Contrary to expectation, none of the visual lobe dimensions was found to correlate significantly with average search times nor with eye movement parameters.

Adult↗
PubMed1993

Effects of cognitive foveal load on a peripheral single-target detection task.

This experiment investigated the effects of foveal cognitive load on a primary peripheral single-target detection task. Four levels of foveal task with cognitive loads involving identification and summation of numerals were used. Number of correct targets detected seemed unaffected by the foveal load in the near periphery but a decrement occurred beyond 7.7 degrees. Response times for correct responses showed large dispersion compared with that for correct locations. At a low cognitive load, foveal task performance showed no deterioration for all eccentricities tested, but at a higher cognitive load performance declined gradually across eccentricities. Mild evidence of tunnel vision was obtained as indicated by the significant interaction of cognitive loads x eccentricities. Resources theory accounted well for the results.

Adult↗
PubMed1993

Visual lobe area mapping for targets on a competing homogeneous background.

Binocular visual lobe areas for two subjects were mapped over part of the visual field. Overall, the lobe shapes were strikingly consistent over a period of 18 months with regard to boundary irregularities and regions of insensitivity. The ratio of eight-axis mapping area to eight-axis area based on complete mapping data was near unity for one subject but very much higher for the other. If these results are typical, the various methods of determining lobe area from measurements taken on a few axes can only give very approximate relative values. It was suggested that the irregular boundary and areas of insensitivity may partly account for the difficulty some subjects experience in locating targets during visual search, even after repeated scanning.

Adult↗
PubMed1991

Display-control relationships for Chinese subjects using three controls.

Display-control stereotypes for direction of motion were tested using a paper-and-pencil test. Seven hundred and eight-three Yunnan Province Chinese subjects of both sexes from a wide range of ages and backgrounds were asked to indicate the control movement they would make to move a display dot in a given direction. Three types of controls and three different planes for the controls were used. The results indicated that although there were some similarities between Western and Chinese stereotypes, the Chinese exhibited stereotypes not generally found in Western subjects.

Adult↗
PubMed1989

Continuation of visual-field mapping for a target embedded in a regular background.

The binocular functional visual-field, which is the area around the fixation point within which a target can be detected, was mapped for two subjects, using a peripherally presented target in a regular background. Over-all the field shapes were strikingly similar to field shapes reported previously for these two subjects and confirmed the presence of boundary irregularities for both subjects.

Adult↗
PubMed1988

The design of school furniture for Hong Kong schoolchildren. An anthropometric case study.

Anthropometric data of Hong Kong schoolchildren have been collected and analysed in order to develop recommendations for the design of chairs and tables for use in Hong Kong Government coeducational schools. The anthropometric data for Hong Kong have been compared with data from a Western population (United Kingdom) and another Asian population (Japan). Five sizes of chair and table combinations have been proposed to accommodate six primary and seven secondary forms (pupils aged from 6 to 18 years). The recommended design dimensions, based on the anthropometric characteristics of the Hong Kong target populations, are discussed in relation to recommendations from previous research in this area.

Journal Article↗