Capture of shrinking targets with realistic shrink patterns

Previous research [Hoffmann, E. R. 2011. “Capture of Shrinking Targets.” Ergonomics 54 (6): 519–530] reported experiments for capture of shrinking targets where the target decreased in size at a uniform rate. This work extended this research for targets having a shrink-size versus time pattern that of an aircraft receding from an observer. In Experiment 1, the time to capture the target in this case was well correlated in terms of Fitts' index of difficulty, measured at the time of capture of the target, a result that is in agreement with the ‘balanced’ model of Johnson and Hart [Johnson, W. W., and Hart, S. G. 1987. “Step Tracking Shrinking Targets.” Proceedings of the human factors society 31st annual meeting, New York City, October 1987, 248–252]. Experiment 2 measured the probability of target capture for varying initial target sizes and target shrink rates constant, defined as the time for the target to shrink to half its initial size. Data of shrink time constant for 50% probability of capture were related to initial target size but did not greatly affect target capture as the rate of target shrinking decreased rapidly with time.     

Multimodal feedback for the acquisition of small targets

This paper examines how multimodal feedback assists small-target acquisition in graphical user interfaces. All combinations of three feedback modes are analysed: non-speech audio; tactile; and pseudo-haptic ‘sticky’ feedback. The tactile conditions used stimulation through vibration (rather than force-feedback), and the sticky conditions were implemented by dynamically reconfiguring mouse control-display gain as the cursor entered the target. Results show that for small, discretely located targets all feedback modes reduce targeting times, with stickiness providing substantial improvements. Furthermore, stickiness and tactile appear to combine well. However, the results of a more ecologically oriented menu-selection task show the need for caution, revealing that excessive feedback can damage interaction though ‘noise’ that interferes with the acquisition of neighbouring targets.     

Effect of target shape on movement time in a Fitts task

Experiments on the effect of target shape in a Fitts movement task are reported. Two experiments investigated the movement time vs. index of difficulty relationship for targets that were square, circular, diamond and triangular in shape. The ratio of standard deviation of hits in the vertical and horizontal directions was constant for all target shapes and thus the movement time could be expressed in terms of the constraint in the direction of motion. Correlation of movement time in terms of an Index of Difficulty based on the standard deviation of hits in the direction of motion showed all data fitting on a single line. Thus the constraint effects of the various shapes occurred from the way in which the hits were distributed within each shape. Various models were tried to account for the effect of the target shape. It was found that the experimental data were best accounted for by a 'cookie-cutter' model in which the target shape was cut into a bivariate normal distribution of hits on the target to obtain a ‘shape factor’ that defined the difficulty of the task relative to the usual rectangular target used in Fitts task experiments.     

Evaluation of fitting of plastic parts

Abstract

As an example of measurement by touch, fitting of plastic parts was studied. Where such requirement is dependent on judgement made by human senses, a number of characteristics must be measured in order to obtain the mechanical characteristics matching those of touch. The degree of fitting judged by touch is quantified by multidimensional scaling, using capsule-shaped plastic parts. Also, the dimensions, shapes and the degree of mechanical fitting are measured and the relationships of these to the quantified senses determined by factor analysis, multivariate data analysis being effective for this purpose.     

CONSTANT VELOCITY IN LIFTING AS A CRITERION OF MUSCULAR SKILL*

The derivation of a measure of skill from changes in velocity throughout a lifting movement was studied. The distances traversed by the wrists in lifting n 10 kg weight to the height of 1-67 in were recorded photographically with the aid of neon lights flashing at 0.1 sec intervals. The values of velocity, acceleration and force were computed at successive stages throughout each movement.

A shift from constant acceleration to constant velocity in movement was significant after training. The estimates of this trend were made by comparing within movement: (a) the mean acceleration with the mean acceleration in the central phase of movement, (b) the kinetic energy developed with the square of mean velocity, (c) the maximum with the mean velocity.

The following effects were shown: as lifting became faster during training the peak velocity approached a constant; the peak velocity was not appreciably increased but the velocity in the initial and final phases of movement was progressively raised towards the peak; this was most pronounced for the mean velocity of lifting 1 -6 m/see and coincided with the greatest work output per litre of expired air. With even faster lifting the constant acceleration reappeared together with a sharp decline of the work output per litre of expired air.

With constant velocity in lifting which involved a vast number of muscles, a reduced force, used with the maximal velocity, reflects the characteristic relation between velocity of contraction and force. With constant acceleration great force coincides with great velocity, suggesting that the elastic element of the muscle engages the contractile mechanism and that a time lag between the motor discharge and its sensory feedback occurs which takes the velocity of the limbs out of control.

On the behavioural level the correspondence, approaching one to one, between the maximum and the mean velocity in movement was statistically a sensitive measure of progress in acquisition of skill.     

A new input device: comparison to three commercially available mouses

This study was conducted to simultaneously compare the postural demands and performance of a new human-centred computer input device to three devices currently on the market. It was hypothesized that the new device would perform as well as the commercial devices while requiring less postural strain. A total of 24 experienced computer users performed a series of modified Steering and Fitts' Law Tests while their postural behaviour was captured using an opto-electric system. Analysis of the postural data revealed strong similarities between the new device and the commercially available devices, including some similarities that are not suggested in the literature. Analysis of the performance data reveals no significant difference between the new device and most commercial devices and suggests further examination of the difference between familiarity and mastery. This study has shown that it is possible to use the new device in a relaxed posture and yet achieve the same accuracy as commercial devices at no more postural risk than when the traditional mouse is used at a customized, ergonomic workstation.     

ERGONOMICS RESEARCH SOCIETY THE SOCIETY'S LECTURE, 1964.

Eight male volnntours, aged 20 to 43 yr, participated in a 1 min run to exhaustion. Six of the subjects had experienced work on the treadmill and ran regularly during the year. By means of a preliminary rim a work load was selected for each subject which would produce exhaustion in 60 sec. The speed of the treadmill was 12.8 kph for all runs except one (14.5 kph) and grade varied from 10 to 20%. The warm up consisted of walking 5.6 kph at a 10% grade for min and preceded the rim by 3 or 5 min. Oxygen consumption ([Vdot]o₂), heart rate (HR), and respiration rate (f) were recorded every 15 sec during the run and during the first 30 sec of recovery. Thereafter, recovory measurements were made during progressively longer intervals for a total of 30 min. [Vdot]0₃, during the run with warm up (2.69± 0.39 L) was significantly greater (p<0.05) than without warm up (2.50±0.41 L). Recovory [Vdot]o₃ and total [Vdot]o₂ (run plus recovory) were not significantly different between the warm up and without warm up runs. The results were not different when net [Vdot]o₂ ([Vdot]o₂minus rest [Vdot]o₃) was compared. A significant increase in heart rate was achieved during rutis with warm up compared to no warm up. Respiration rates were also increased with warm up but not significantly. The conclusion was that under the conditions of this study, warm up is of energetic benefit in preparing for a short exhaustive run.     

Data-entry keyboard geometry and keying movement times

Abstract

Experiments on fifteen simulated keyboards with different key sizes and inter-key spacings are reported. It was found that the movement time on these keyboards was well described by the model of Drury (Drury and Hoffmann 1992). Minimum movement times occurred when the inter-key spacing was approximately equal to the finger pad size. There was found to be an effect of the number of keys moved, which was not predicted by the model. This effect remained in a further experiment in which the target keys were marked.     

Effects of age and psychomotor ability on kinematics of mouse-mediated aiming movement

The objective of this research is to understand the influence of age and age-related psychomotor ability on the process of mouse-mediated aiming movement. It is premised on the notions that (1) mouse-mediated aiming movements can be better understood via studying its kinematics and (2) age is a surrogate variable in kinematic differences, and that age-influenced fundamental factors such as psychomotor ability may have a more direct effect. As expected, age kinematic differences were detected. However, when comparing with age, age-influenced psychomotor ability (i.e. manual dexterity) contributed more substantially to the variances of kinematics in the ballistic phase. For homing phase, in addition to manual dexterity, age-influenced wrist–finger speed was also a significant contributor. In future studies, it is suggested that components of visual processing should be included for better understanding of its role as an age-influenced fundamental ability in aiming movements. Applications of this research are discussed.

Practitioner Summary: This paper presents empirical data showing age effects in movement kinematics are chiefly mediated by age-related changes in psychomotor ability. Our findings provide additional data for existing and newer performance enhancement solutions, especially for those targeting older adults.     

MANY MESSAGES FROM FEW SOURCES

Two methods of presenting a given number of visual messages have been compared. (1) Each message was displayed by a separate source. (2) All combinations of n sources were used to display 2n?1 alternative messages. These were called Separate Sources (S) Displays and Combined Sources (C) Displays, respectively. Comparisons were- made between displays of 3, 7 and 15 alternative stimuli. The criteria of efficiency were speed and accuracy of verbal response. At the 3 and 7-choice levels there was no significant difference between the rates of gain of information from the two types of display. At the 15-choice level, subjects gained information significantly more efficiently from the S display. It is concluded that C displays can be used to advantage in signalling systems which must present up to 7 alternative stimuli.     

Visual and manual loadings with QWERTY-like ambiguous keyboards: Relevance of letter-key assignments on mobile phones

Mobile phone touchscreens have many ergonomic problems related to text entry. Previous studies, which attempted to use ambiguous keyboards to resolve problem of small keys, focused on the disambiguation process without consideration of the user loading on graphic user interface. This study investigates user loadings, which interfere with performance in the key selection phase when using an ambiguous keyboard. Hence, three QWERTY-like ambiguous keyboards and a standard QWERTY keyboard were compared via visual search and manual operation experiments. The visual search experiment shows that layouts with many letters per key were strongly related to long visual search times, and layouts with large keys were operated faster and more accurately in the manual operation experiment. Consequently, the trade-off between visual and manual loading differed among different letter-key assignments. This study is important in that it elucidates the impacts of visual and manual loadings on ambiguous keyboards, as well as in providing user interface designers with an enhanced understanding of how to design ambiguous keyboards based on user criteria.Relevance to industryAmbiguous keyboard designs in previous studies were generally far from the actual needs of users. This study examines the factors affecting text entry performance of users via the user-centered approach, improving the understanding of designers.     

The use of ballistic movement as an additional method to assess performance of computer mice

This study investigates an additional method for independently evaluating performance of speed and accuracy of computer mice, based on five parameters of the initial submovement when aiming at a target. This first submovement is known to be carried out in a ballistic manner and hence the Fitts-type aiming movement may be studied by means of the established relationships for ballistic movement. To test the ballistic movement method, eight participants used four different computer mice to execute ballistic movements and Fitts-type aiming movements. Regression tests showed that the Fitts movement time was well correlated with the time and stopping-variable error of ballistic movement, implying that measuring ballistic movement parameters can predict the performance of Fitts-type aiming movements. More importantly, the use of ballistic movement method allows independent assessments of the speed and accuracy, providing additional information for input devices assessment and designs.Relevance to industryThe study illustrates the close correspondence between input device evaluation using the proposed ballistic movement method and Fitts' law. The ballistic movement method allows independent measures of speed and four types of accuracy, which should benefit input devices assessment and designs.     

A shrinking technique for complex object decomposition

A shrinking technique is described for the segmentation of a 2D complex object, represented by a binary array, into compact subobjects. A novel feature of the technique is that it uses the distance values on the skeleton of the object to estimate the number of shrinking steps needed in order to decompose the object.     

The performance of computer input devices in a vibration environment

This study investigates the performance of a touch screen, mouse and trackball in a motion environment. A Stewart motion platform was used to generate a six-degree-of-freedom motion environment. Participants were placed in an environment where vehicle vibration was simulated. Tasks were used according to Fitts' Law to obtain the movement time, error rate, index of performance and throughput of each input device. The results showed that during static conditions, the touch screen gave the best results. However, in the vibration environment, the mouse gave the best results. The trackball is the worst of the three. The error rate and end-point variation tends to increase for the touch screen in the vibration environment.

Statement of Relevance: This study investigates the performance of a pointing device in a vibration environment. The results showed that during static conditions, the touch screen gave the best results. However, in the vibration environment, the mouse gave the best results. The track ball is the worst of the three. This research achievement can help human–computer interaction design in various dynamic environments such as in sea and land vehicles.     

The effect of age on the hand movement time during machine paced assembly tasks for female workers

The share of older adults in the workforce is increasing in many countries. In the manufacturing industry a high proportion of assembly tasks are machine paced. Previous studies have shown that older adults tend to have longer movement times than younger adults when working at a self-selected pace. However, it is unclear whether older adults can obtain the same hand movement time as a younger group when performing machine paced work at the assembly line. In the current study, 10 older and 10 younger female participants performed simulated light-duty assembly tasks during which the hand movement times were recorded. The results showed that the older participants were capable of working at the set pace and there was no significant difference between age groups in hand movement times (989.9 msec vs. 986.6 msec, p = 0.5647). A likely explanation to the results is that the older participant had to work closer to their physical limits or capacity in order to compensate for the age effect on movement time.     

菲波那奇数列变栅格的数据收缩聚类方法研究*

利用菲波那奇数列对栅格尺度进行确定,结合边界确定方式和焦点定位方法获得一种有效的高维数据收缩聚类方法。从基于密度的聚类方法出发,研究密度跨距基础上的良好聚类时变栅格的获取方式,引入菲波那奇数列获取变栅格相应的网格;在实际数据聚类的过程中,采用数据点吸引的方式确定数据质心,通过数据移动和收缩获得最终聚类的焦点和形状。仿真实验的结果表明,本方法可以有效运用于二维和高维数据的聚类分析,在准确获取现有数据内部结构的基础上,具有一定的防噪声作用,可以依据焦点实现数据的有效收缩。     

Extended Fitts' law for 3D pointing tasks using 3D target arrangements

This study explored an extended 3D Fitts' model, which was more appropriate than the original Fitts' model for pointing tasks in 3D environment. The inclination angle and azimuth angle for spherical coordinate system were added to Fitts' original model formulation. Experiments were conducted by manipulating the distance to the target, the size of target, and the 3D target arrangement, which were described using the two angles of inclination (θ1) and azimuth (θ2). Given the starting point as the center of the coordinates, θ1 was the angle between the positive y-axis and the target location, while θ2 was the angle between the positive x-axis and the projected target location on the x–z plane. All four variables were found to be significant for the movement time (MT) (p < 0.0001). After incorporating the two variables, θ1 and θ2, into the original Fitts' model, the extended Fitts' model with 3D target arrangements for spherical coordinate system showed better agreement with the empirical data than previous models in terms of the correlation coefficient and the standard error of the residuals for the measured and predicted MTs.Relevance to industryThis study presents an extended Fitts' model with a higher degree of predictability than previous studies for pointing task in three-dimensional space. In many situations, people implement pointing tasks in a three-dimensional environment, so it is important for designers to predict human performance accurately. Instead of using Euclidean coordinate system, spherical coordinate system can be also used for 3D pointing tasks. The extended model with spherical coordinate system can be used during the design and evaluation stage of the development process to help designers and developers.     

空间目标检测序列图像中恒星目标抑制

针对固定指向地基天文光电探测系统中数量众多、成像相似的恒星目标对空间目标检测的干扰,提出一种基于时空域融合处理的恒星目标抑制算法。在时域上改进图像差分算法,采用时域膨胀差分抑制恒星目标;在空域上对检测到的恒星目标采用数学形态学重构来恢复恒星目标的完整星像,进而将形态学重构前后的图像相消来抑制恒星目标。根据时空域融合处理机制的不同,给出了两种融合处理方法抑制恒星目标。通过实测数据对比,结果表明本文算法达到了良好的恒星目标抑制效果:1)能够较好地抑制恒星目标及其边缘像素;2)暗弱恒星目标也得到较好地抑制;3)恒星目标抑制后空间目标的信噪比得到了较大提升。     

有效提高SVM参数搜索效率的样本集缩减策略

核函数及相关参数的选择是支持向量机中的一个重要问题, 它对模型的推广能力有很大的影响。当有大量样本参与训练的时候,寻找最优参数的网格搜索算法将消耗过长的时间。针对这一问题,提出一种舍弃非支持向量的样本点的策略,从而缩减了训练样本集。能够在基本保持原有测试准确度的前提下,将搜索时间减少一半。     

Effect of varying target height in a Fitts' movement task

Experiments are reported of the effect on movement times of varying target height in a Fitts' type of experiment. Data show that there are three well defined regions of control. The first of these, when the index of difficulty based on the target widdi in the direction of motion is larger than that based on the vertical height of the target, is dominated by the constraint in the direction of motion. The second is a transitional region where both vertical and horizontal constraints are effective. The third region is one where the vertical constraint dominates the times for the movement. Fitts' law is found to be applicable in the first and third regions. The same pattern of movement times, as a function of die two IDs, is obtained for discrete and reciprocal movements. As well, die time on target for die reciprocal movements demonstrates this same pattern.