Divided attention in experienced young and older drivers: lane tracking and visual analysis in a dynamic driving simulator.

A simulated driving task that required the simultaneous execution of two continuous visual tasks was administered to 12 healthy young (mean age 26.1 years) and 12 healthy older (mean age 64.4 years) experienced and currently active drivers. The first task was a compensatory lane-tracking task involving a three-dimensional road display. The second task was a timed, self-paced visual analysis task involving either a vocal or manual binary response to dot patterns projected within the road display. Using adaptive tasks, single-task difficulty was individually adjusted for each subject. To control for individual differences in attention allocation strategy, the dual task was performed according to three different sets of instructions based on the relative importance of each task. Compared with young adults, older adults showed a significantly decreased ability to divide attention. This effect was apparent in lane tracking and in the accuracy of visual analysis. The impairment of divided attention was less pronounced in the vocal condition than in the manual one. This suggests that difficulty in integrating responses may be an important determinant of poor dual-task performance in old age.     

Mental workload and cognitive task automaticity: an evaluation of subjective and time estimation metrics

Abstract

The evaluation of mental workload is becoming increasingly important in system design and analysis. The present study examined the structure and assessment of mental workload in performing decision and monitoring tasks by focusing on two mental workload measurements: subjective assessment and time estimation. The task required the assignment of a series of incoming customers to the shortest of three parallel service lines displayed on a computer monitor. The subject was either in charge of the customer assignment (manual mode) or was monitoring an automated system performing the same task (automatic mode). In both cases, the subjects were required to detect the non-optimal assignments that they or the computer had made. Time pressure was manipulated by the experimenter to create fast and slow conditions. The results revealed a multi-dimensional structure of mental workload and a multi-step process of subjective workload assessment. The results also indicated that subjective workload was more influenced by the subject's participatory mode than by the factor of task speed. The time estimation intervals produced while performing the decision and monitoring tasks had significantly greater length and larger variability than those produced while either performing no other tasks or performing a well practised customer assignment task. This result seemed to indicate that time estimation was sensitive to the presence of perceptual/cognitive demands, but not to response related activities to which behavioural automaticity has developed.     

Gender difference in mobile phone use and the impact of digital device exposure on neck posture

This cross-sectional study aimed to identify gender differences in the cervical postures when young adults were using mobile phones, as well as the correlations between the postures and the digital devices use (computer and mobile phone). Questionnaires regarding the habits of computer and mobile phone use were administrated to 429 subjects aged from 17 to 33 years old (19.75 ± 2.58 years old). Subjects were instructed to stand habitually and use a mobile phone as in daily life; the sagittal head and cervical postures were measured by head flexion, neck flexion angle and gaze angle. Male participants had a significantly larger head flexion angle (96.41° ± 12.23° vs. 93.57° ± 12.62°, p = 0.018) and neck flexion angle (51.92° ± 9.55° vs. 47.09° ± 9.45°, p < 0.001) than females. There were significant differences in head (F = 3.62, p = 0.014) and neck flexion (F = 3.99, p = 0.009) between different amounts of computer use.

Practitioner Summary: We investigated possible gender differences in head and neck postures of young adults using mobile phones, as well as the potential correlations between these postures and digital device use. We found that males displayed larger head and neck flexion angles than females, which were associated with the amount of computer use.     

Rethinking Reading for Age From Paper and Computers

The human–computer interaction research community has long been interested in the role of age in the use of computing devices. The current availability of large high-resolution displays and a growing community of older adults who use computers on a regular basis are examples of a changing landscape of users and devices that calls for a reevaluation of what we know about age and computers. This article presents two studies comparing the performance of young and older adults in reading tasks. In our studies, older adults outperformed young adults in terms of reading times and reading comprehension regardless of medium (paper or computer display). In addition, the overlap of confidence intervals for reading times and comprehension by medium suggests participants performed equally well regardless of medium. Both findings are in contrast to results from similar studies from the 1980s and 1990s.     

Light pen use and practice minimize age and hand performance differences in pointing tasks

We contrasted performance with mouse and light pen input devices for younger, middle-aged, and older adults (N = 72) who were experienced mouse users. Participants used both preferred and nonpreferred hands to perform a menu target selection task. The light pen minimized age differences in performance relative to the mouse. Older adults were more lateralized on a handedness test than young adults and were less efficient using their nonpreferred hand. With practice, older adults improved their response time more than other age groups did. The mouse was rated as more acceptable and easier to use than the light pen across trials, despite the performance advantage of the light pen for all age groups. Usability ratings correlated moderately with performance. A benefit-cost analysis indicated that the more efficient light pen might cover its greater initial cost within 11 months for an older adult and within 23 months for a younger adult. Actual or potential applications of this research include advising older adults to persist with practice for new input devices, advising those who must switch to their non-preferred hand to select a direct positioning device, and providing a methodology for determining the potential payback interval when switching to a faster, though more expensive, input device.     

Input devices for web browsing: age and hand effects

The work reported in this paper examined performance on a mixed pointing and data entry task using direct and indirect positioning devices for younger, middle-aged, and older adults (n=72) who were experienced mouse users. Participants used both preferred and non-preferred hands to perform an item selection and text entry task simulating a typical web page interaction. Older adults performed more slowly than middle-aged adults who in turn performed more slowly than young adults. Performance efficiency was superior with the mouse for older adults only on the first two trial blocks. Thereafter mouse and light pen yielded equivalent performance. For other age groups, mouse and light pen were equivalent at all points of practice. Contrary to prior research revealing superior performance with a light pen for pure pointing tasks, these results suggest that older adults may initially perform worse with a light pen than a mouse for mixed tasks.     

Manual dexterity of older Mexican American adults: a cross-sectional pilot experimental investigation

This paper reports results from an experimental pilot study performed to quantify the manual dexterity of older Mexican American adults. The Purdue pegboard test, a two-arm coordination test, and a hand-tool dexterity test were used in this study. To enable cross-sectional comparisons of manual dexterity measures of older Mexican American adults with young Mexican American adults, these tests were administered to 18 older Mexican American adults aged 63–85 (mean age: 71.3 years, SD: 7.0 years), recruited from senior recreation centers in El Paso, and eighteen young adults aged 21–32 (mean age: 25.6 years, SD: 3.8 years) recruited from the student body at the University of Texas at El Paso. For the Purdue pegboard test, the number of pegs placed in 30 s using the preferred hand, the non-preferred hand, and both hands were first individually monitored. Then, scores on an assembly task using the Purdue pegboard were obtained. For the two-arm coordination test, participants were required to trace a star pattern with a stylus using both hands. The time for task completion and the number of errors made during task performance were monitored. For the hand-tool dexterity test, participants were required to use common hand tools and remove nuts and bolts from one side of a wooden upright, and to assemble nuts and bolts in the corresponding holes on the other side of the upright. The time taken for task completion was recorded. Since modified Levene's test showed equality of variances, two sample t-tests, comparing the mean responses of older adults with the mean responses of young adults for each individual test, were conducted. Results indicate that responses for the older adults were statistically significant different (p<0.001) from young adults for all Purdue pegboard tasks. On the average, older adults performed significantly slower (p<0.001) than young adults on the two-arm coordination test, and committed more errors before task completion (p<0.05). Older adults also took longer to complete the hand-tool dexterity task compared to their younger counterparts (p<0.05). In addition to the t-tests, manual dexterity performance measures from older adults were regressed with age to determine the cross-sectional age effects on manual dexterity measures. Results indicate that all Purdue pegboard performance measures were significantly affected by age (p<0.05). The time to complete the two-arm coordination test was significantly linearly related to age (p<0.05). However, the number of errors committed by older adults in the performance of the two-arm coordination test was not significantly linearly related to age. Time to complete the hand-tool dexterity was also significantly linearly related to age (p<0.05). Accommodating age-related changes in manual dexterity is important for job design in industry, especially in industries employing older adults requiring significant assembly and hand-tool use.

Relevance to industry

Given the aging of the industrial workforce, it is important to understand how manual dexterity is affected by age, so that jobs requiring significant manual dexterity for task initiation, task performance and task completion are designed to fit older adult dexterity levels.     

Age-related biomechanical differences during asymmetric lifting

This study investigated age-related biomechanical differences during asymmetric lifting. Eleven younger and twelve older participants were instructed to lift loads of different weights to an asymmetric destination. The trunk kinematics and low back moments were examined. The results showed that older adults adopted safer lifting strategies compared with younger adults. Specifically, the peak trunk sagittal flexion angle was 32% lower and the peak trunk transverse twisting angle was 22% lower in older adults compared with those in younger adults. It was also found that the average low back moment in the deposit phase was 32% higher in older adults than that in younger adults, most probably due to the age-related increased body weight. Based on these findings and the fact of age-related decreased muscle strengths, physical exercise programs were suggested to be more effective than instructions of safe lifting strategies in LBP risk reduction during asymmetric lifting for older adults. For younger adults, safe lifting strategy instructions might be effective to reduce risks of LBP.     

The effects of multimodal feedback on older adults' task performance given varying levels of computer experience

This experiment examines the effect that computer experience and various combinations of feedback (auditory, haptic, and/or visual) have on the performance of older adults completing a drag-and-drop task on a computer. Participants were divided into three computer experience groups, based on their frequency of use and breadth of computer knowledge. Each participant completed a series of drag-and-drop tasks under each of seven feedback conditions (three unimodal, three bimodal, one trimodal). Performance was assessed using measures of efficiency and accuracy. Experienced users responded well to all multimodal feedback while users without experience responded well to auditory-haptic bimodal, but poorly to haptic-visual bimodal feedback. Based on performance benefits for older adults seen in this experiment, future research should extend investigations to effectively integrate multimodal feedback into GUI interfaces in order to improve usability for this growing and diverse user group.     

The influence of desk and display design on posture and muscle activity variability whilst performing information technology tasks

Desk design and computer display height can affect posture and muscle activation during computer use. Amplitudes of postural variables and muscle activity during computer use do not explain the results from epidemiological studies of musculoskeletal discomfort and disorders related to computer use. The purpose of this study was to assess variability of posture and muscle activity during work with two computer display heights and book/paper, in conjunction with a curved desk designed to provide forearm support and a traditional, straight desk.18 male and 18 female participants performed 10-min tasks involving keying, mousing, reading and writing in six desk/display conditions. 3D posture and surface emg were assessed for the final 2 min of each task.The curved desk resulted in greater postural and muscle activity variation, suggesting an advantage of this supportive surface over the straight desk. There was little difference in variability associated with the two display heights. However, greater variability of posture and muscle activity was evident with the book/paper condition. Non-touch typists had greater neck flexion variation.The design of information technology tasks and workstations can influence the short term variation in posture and muscle activity. Variation is influenced independently of mean postures and muscle amplitudes and therefore needs to be considered to adequately assess the risk of musculoskeletal disorders.     

Muscle Activity and Comfort Perception on Neck,Shoulder, and Forearm While Using a Tablet Computer at Various Tilt Angles

Tablet computers have become ubiquitous. There is a serious risk that using tablets may lead to musculoskeletal disorders. This research aims to investigate, for tablet computer users, the musculature load and comfort perception of the engaged upper extremity for three angles of viewing and common task types performed at a computer workstation. Thirty healthy adults were recruited. A 3 × 2 repeated experimental design with tilt angle (22.5°, 45°, and 67.5° from horizontal) and task type (movie watching vs. game playing) was employed. The muscular activity of the upper extremity was assessed by electromyography measurement. Subjective comfort ratings were collected using the visual analogue scale. The results showed that when tablets were mounted at a high tilt angle (67.5°), neck muscle activity was low; however, when the tablet computer was mounted at a low tilt angle (22.5°), shoulder forward flexion activity was low, particularly during the game-playing task. This article suggests that users who feel musculoskeletal discomfort in the neck area increase the angle of their tablet computers to decrease neck stress and that users who have musculoskeletal discomfort in the shoulder area position the tablet computer at a lower tilt angle to decrease shoulder stress.     

Effects of fire fighter protective ensembles on mobility and performance

Many studies have shown that fire fighter turnout gear and equipment may restrict mobility. The restriction of movement is usually due to a decrease in range of motion (ROM). It is important to know how much the decrease in ROM affects performance. The aim of this study was to determine the effects of fire fighter protective ensembles on mobility and performance by measuring static and dynamic range of motion (ROM) and job-related tasks. Eight healthy adults (5 males, 3 females), aged 20-40 years, participated in this study. The study consisted of measuring a battery of motions and fire fighter specific tasks while wearing a standard fire fighter ensemble (SE) or regular light clothing (baseline or BL). Several BL ROM tests were significantly (p < 0.05) different from the SE test, including a decrease in shoulder flexion, cervical rotation and flexion, trunk lateral flexion, and stand and reach. There was a significant decrease in time from SE to baseline performing the one-arm search task and object lift. These overall findings support the need for a comprehensive ergonomic evaluation of protective clothing systems to ascertain human factors issues. The development of a Standard Ergonomics Test Practice for further use in laboratories that conduct personal protective systems evaluations using human test subjects is recommended.     

Relationship analysis between body flexion angles and smartphone tilt during smartphone use

Although smartphones are used as essential devices in everyday life, many users are exposed to joint diseases owing to prolonged use. The objectives of this study were to analyze how posture and smartphone tasks affect various body flexion angles and develop an algorithm to classify posture/task and estimate body flexion angles using smartphone tilt data. Eighteen participants performed two tasks (playing a game and reading news) in two postures (sitting and standing) in a laboratory environment. The three-axis orientation data (azimuth, pitch, and roll) of the smartphone and the participants’ body flexion angles were measured simultaneously. This study found that the cervical, thoracic, lumbar, and overall flexion angles were all statistically significantly different depending on the posture of the smartphone user, and the cervical flexion angle was significantly different depending on the task. Furthermore, task and task × posture can be classified with high accuracy based on smartphone tilt data, and tilt data had a high correlation with body flexion angles. Relevance to industry: The results of this study can be used as a reference for designing various products and interfaces for neck health. The results can be applied as a smartphone alarm or a built-in application, which can inform the user of the need to stretch his or her neck.     

Age-related differences in the maintenance and modification of automatic processes: arithmetic Stroop interference

This experiment was designed to investigate whether well-learned "automatic" processes remain stable as a function of age, as well as to determine whether the ability to modify these automatic processes is disrupted for older adults. We used an arithmetic Stroop task to measure the stability of an automatic process. Nineteen young (mean age 22) and 19 old (mean age 75) adults participated in three experimental sessions, each of which consisted of 15 blocks of 30 trials. Although the young subjects had faster verification times overall than did the old adults, both young and old subjects showed significant interference effects. For the young adults, there was a decrease in the interference effect with practice, which suggested that they were learning to inhibit the automatic process of performing the arithmetical operation. However, the old adults showed no significant decrease in the associative interference effects. This implies that the older adults were impaired in their ability to inhibit automatic processes, even when those processes interfered with performance. Theoretical and practical training implications are discussed.     

Wrist postures in the general population of computer users during a computer task

Computer activities have commonly been linked to the development of musculoskeletal disorders (MSDs) in the upper limbs. However, to understand the effects computer use has on such disorders, it is necessary to identify and classify the movements involved in performing common computer tasks, one of these being typing. Motion analysis techniques were adopted to determine the movements involved during a typing task. This involved markers being placed on the knuckles, wrists and forearms of participants. This marker configuration allowed for the flexion, extension, radial deviation, ulnar deviation and a combination of these movements to be calculated. The results in one plane of motion show a mean extension|flexion and radial|ulnar deviation of 18.825°?±?10.013° and 5.228°?±?11.703° respectively. The most common position in two planes of motion was 20° extension with a simultaneous 20° ulnar deviation (10.72%). The results depict an alternative method of categorizing wrist positions in two planes during computer use. Coincident wrist postures should be addressed as opposed to motion in a single plane as these postures may result in different ergonomic risk factors developing.     

Effects of age and its interaction with task parameters on lifting biomechanics

This study investigated the age-related differences in lifting biomechanics. Eleven younger and 12 older participants were instructed to perform symmetric lifting tasks defined by different combinations of destination heights and load magnitudes. Lifting biomechanics was assessed. It was found that the trunk flexion in the starting posture was 32% lower and the peak trunk extension velocity was 46% lower in older participants compared with those in younger ones, indicating that older adults tended to use safer lifting strategies than did younger adults. Based on these findings, we recommend that physical exercise programmes may be a more effective ergonomic intervention for reducing the risks of low back pain (LBP) in lifting among older workers, compared with instructions of safe lifting strategies. As for younger workers, instructions of safe lifting strategies would be effective in LBP risk reduction.     

Characterization of a laboratory model of computer mouse use - applications for studying risk factors for musculoskeletal disorders

In the present study, we assessed the wrist kinetics (range of motion, mean position, velocity and mean power frequency in radial/ulnar deviation, flexion/extension, and pronation/supination) associated with performing a mouse-operated computerized task involving painting rectangles on a computer screen. Furthermore, we evaluated the effects of the painting task on subjective perception of fatigue and wrist position sense. The results showed that the painting task required constrained wrist movements, and repetitive movements of about the same magnitude as those performed in mouse-operated design tasks. In addition, the painting task induced a perception of muscle fatigue in the upper extremity (Borg CR-scale: 3.5, p<0.001) and caused a reduction in the position sense accuracy of the wrist (error before: 4.6 degrees , error after: 5.6 degrees , p<0.05). This standardized painting task appears suitable for studying relevant risk factors, and therefore it offers a potential for investigating the pathophysiological mechanisms behind musculoskeletal disorders related to computer mouse use.     

Comparison of posture and muscle control pattern between male and female computer users with musculoskeletal symptoms

The primary purpose of this study was to compare the posture and muscle control patterns between male and female computer users with musculoskeletal symptoms. Forty computer users were recruited. Each subject performed a preferred speed typing, a fast speed typing, and a repetitive mouse task. The independent variables were gender, typing speed, and time. There were significant differences between genders for head and neck flexion angles when they were performing the preferred speed typing task. Significant differences between genders were also found for upper extremity angles when they were performing the repetitive mouse task. Male computer users had a smaller root mean square of the right extensor digitorium than females. In general, postural differences were significant between genders, even when the subjects' table and chair were adjusted to meet their anthropometry. Our results suggest that modifications of the computer working environment may be different between genders.     

Acceptability of a custom-designed game,CityQuest, aimed at improving balance confidence and spatial cognition in fall-prone and healthy older adults

Virtual reality or video games show great potential as low-cost and effective interventions for improving balance and cognitive function in older adults. This research describes the design and acceptability of a serious game (CityQuest) aimed at improving balance confidence, spatial navigation, and perceptual function in older adults with the use of a virtual environment and a balance board. Community-dwelling healthy (N?=?28) and fall-prone (N?=?28) older adults were pseudo-randomly assigned to train with CityQuest or one of two control games developed to evaluate the specific effects of the CityQuest game. Following completion of 10 training sessions, participants completed questionnaires measuring their acceptability of the game as a falls-related intervention, game experience, and subjective cognitive or balance confidence changes associated with the game. The results revealed high acceptance scores of the game and positive game experiences for all three game conditions. Older adults prone to falls reported a greater reduction in fear of falling and greater improvement in vigilance following training, compared to healthy older adults. These findings suggest that a serious game based on VR technology that trains both motor and cognitive processes is perceived to be beneficial and acceptable to healthy and fall-prone older adults.     

Understanding sources of user variability in computer-based data entry performance

The pervasive use of computers in work settings implies that an increased number of workers, with varying levels of skills and abilities, will be performing computerbased tasks. This study investigated the impact of age, cognitive abilities, and computer experience on the performance of a real world data entry task. One hundred and ten subjects, ranging in age from 20 - 75 years, performed the task for nine hours following task training. The results indicated that abilities such as visuo-spatial skills, motor skills and processing speed had a significant impact on performance as did age and prior computer experience. With respect to age, the older participants completed less work than the younger and middle-aged subjects. Age differences in psychomotor skills and processing speed appeared to be important factors underlying age effects. In fact, the data indicated that after controlling for differences in these abilities age was no longer a significant predictor of work output. Further, after controlling for differences in work output the older people made fewer errors than the younger people. Overall the data suggest that older people will be at a disadvantage in the performance of computer-based data entry work to the extent to which speed of responding is emphasized. However, if speed of responding is not a critical element of performance they will be able to achieve comparable levels of performance to that of younger people.