Age differences in the control of a precision reach to grasp task within a desktop virtual environment

The purpose of this experiment is to investigate the fine motor performance of young and older adults on a reach to grasp task in a desktop virtual environment with increasing precision requirements. Aging brings about potential loss of an individual's function due to disease, injury, or the degenerative nature of aging itself. Three-dimensional virtual environments have been identified as systems with good potential to ameliorate such problems in older individuals, and precise fine motor skills represent an important class of functional skills. Two groups of participants (Young, n=10, mean age 21.3 years, range 20–24, senior, n=10, mean age 70.7 years, range 60–85) performed a reach to grasp in a desktop virtual environment with simple, low contrast graphics. Results indicate that visual feedback of the hand for sensory guidance of movement did not improve motor performance for either group, and that as precision requirements of the task increased, age group differences in movement time and peak grasp aperture also increased. These findings extend the literature on age group differences in human motor control across the lifespan and differ from previous studies which showed presence of visual feedback of the hand improved motor performance in young adults. Differences in luminance contrast levels in past studies and the current one suggest that control over this feature of the visual scene is an important design consideration for all end-users and warrants additional investigation. Additional recommendations for age-specific design of three dimensional user interfaces include usage of tangibles that are sufficient in size to limit detrimental effects for older adults.     

An experimental study on the role of graphical information about hand movement when interacting with objects in virtual reality environments

In this series of experiments, we investigated whether a crude representation of the hand that was extinguished at movement onset improved performance when compared to a no-feedback situation. Subjects performed simple reach to grasp movements in a virtual environment in two experiments. In Experiment 1, trials were blocked so that subjects were aware that a graphical representation of the hand would either be available throughout the movement (FA), be removed at movement onset (FAB), or not be available (NF). In Experiment 2, trials were randomized so that subjects were unaware of whether feedback would be available throughout the trial or removed at movement onset. Our results indicated that when subjects were aware of the availability of graphical feedback, the FAB condition improved performance compared to the NF condition. Furthermore, movement time was similar in the two feedback available conditions (FA, FAB). In contrast, for the randomized trial presentation, the positive influence of the FAB condition was diminished. These results suggest that visual feedback available prior to movement onset can be used to calibrate the proprioceptive system and improve performance over a no feedback situation. These results can be applied by designers of virtual environments to solve problems related to occlusion of important environmental information by the hand as users reach to grasp and manipulate objects.     

Effects of four types of non-obtrusive feedback on computer behaviour, task performance and comfort

This study investigated the effects of non-obtrusive feedback on continuous lifted hand/finger behaviour, task performance and comfort. In an experiment with 24 participants the effects of two visual and two tactile feedback signals were compared to a no-feedback condition in a computer task. Results from the objective measures showed that all types of feedback were equally effective to reduce lifted hand/finger behaviour (effectiveness) compared to absence of feedback, while task performance was not affected (efficiency). In contrast to objective measures, subjective user experience was significantly different for the four types of feedback signals. Continuous tactile feedback appeared to be the best signal; not only the effectiveness and efficiency were rated reasonable, it also scored best on perceived match between signal and required action. This study shows the importance of including user experiences when investigating usability of feedback signals. Non-obtrusive feedback embedded in products and environments may successfully be used to support office workers to adopt healthy, productive and comfortable working behaviour.     

Vision for Performance in Virtual Environments: The Role of Feedback Timing

This work explores how people use visual feedback when performing simple reach-to-grasp movements in a tabletop virtual environment. In particular we investigated whether visual feedback is required for the entire reach or whether minimal feedback can be effectively used. Twelve participants performed reach-to-grasp movements toward targets at two locations. Visual feedback about the index finger and thumb was provided in four conditions: vision available throughout the movement, vision available up to peak wrist velocity, vision available until movement initiation, or vision absent throughout the movement. It was hypothesized that vision available until movement onset would be an advantage over a no vision situation yet not attain the performance observed when vision was available up to peak velocity. Results indicated that movement time was longest in the no vision condition but similar for the three conditions where vision was available. However, deceleration time and peak aperture measures suggest grasping is more difficult when vision is not available for at least the first third of the movement. These results suggest that designers of virtual environments can manipulate the availability of visual feedback of one's hand without compromising interactivity. This may be applied, for example, when detailed rendering of other aspects of the environmental layout is more important, when motion lag is a problem or when hand/object concealment is an issue.     

Helping older pedestrians navigate in the city: comparisons of visual,auditory and haptic guidance instructions in a virtual environment

Preserving older pedestrians’ navigation skills in urban environments is a challenge for maintaining their quality of life. However, existing aids do not take into account older people’s perceptual and cognitive declines nor their user experience, and they call upon sensory modalities that are already used during walking. The present study was aimed at comparing different guidance instructions using visual, auditory, and haptic feedback in order to identify the most efficient and best accepted one(s). Sixteen middle-age (non-retired) adults, 21 younger-old (young-retired) adults, and 21 older-old (old-retired) adults performed a navigation task in a virtual environment. The task was performed with visual feedback (directional arrows superimposed on the visual scenes), auditory feedback (sounds in the left/right ear), haptic feedback (vibrotactile information delivered by a wristband), combinations of different types of sensory feedback, or a paper map. The results showed that older people benefited from the sensory guidance instructions, as compared to the paper map. Visual and auditory feedbacks were associated with better performance and user experience than haptic feedback or the paper map, and the benefits were the greatest among the older-old participants, even though the paper-map familiarity was appreciated. Several recommendations for designing pedestrian navigation aids are proposed.     

Coupled dynamical system based arm–hand grasping model for learning fast adaptation strategies

Performing manipulation tasks interactively in real environments requires a high degree of accuracy and stability. At the same time, when one cannot assume a fully deterministic and static environment, one must endow the robot with the ability to react rapidly to sudden changes in the environment. These considerations make the task of reach and grasp difficult to deal with. We follow a Programming by Demonstration (PbD) approach to the problem and take inspiration from the way humans adapt their reach and grasp motions when perturbed. This is in sharp contrast to previous work in PbD that uses unperturbed motions for training the system and then applies perturbation solely during the testing phase. In this work, we record the kinematics of arm and fingers of human subjects during unperturbed and perturbed reach and grasp motions. In the perturbed demonstrations, the target’s location is changed suddenly after the onset of the motion. Data show a strong coupling between the hand transport and finger motions. We hypothesize that this coupling enables the subject to seamlessly and rapidly adapt the finger motion in coordination with the hand posture. To endow our robot with this competence, we develop a coupled dynamical system based controller, whereby two dynamical systems driving the hand and finger motions are coupled. This offers a compact encoding for reach-to-grasp motions that ensures fast adaptation with zero latency for re-planning. We show in simulation and on the real iCub robot that this coupling ensures smooth and “human-like” motions. We demonstrate the performance of our model under spatial, temporal and grasp type perturbations which show that reaching the target with coordinated hand–arm motion is necessary for the success of the task.     

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.     

Effectiveness of auditory and tactile crossmodal cues in a dual-task visual and auditory scenario

Abstract

In this study, we examined how spatially informative auditory and tactile cues affected participants’ performance on a visual search task while they simultaneously performed a secondary auditory task. Visual search task performance was assessed via reaction time and accuracy. Tactile and auditory cues provided the approximate location of the visual target within the search display. The inclusion of tactile and auditory cues improved performance in comparison to the no-cue baseline conditions. In comparison to the no-cue conditions, both tactile and auditory cues resulted in faster response times in the visual search only (single task) and visual–auditory (dual-task) conditions. However, the effectiveness of auditory and tactile cueing for visual task accuracy was shown to be dependent on task-type condition. Crossmodal cueing remains a viable strategy for improving task performance without increasing attentional load within a singular sensory modality.

Practitioner Summary: Crossmodal cueing with dual-task performance has not been widely explored, yet has practical applications. We examined the effects of auditory and tactile crossmodal cues on visual search performance, with and without a secondary auditory task. Tactile cues aided visual search accuracy when also engaged in a secondary auditory task, whereas auditory cues did not.     

Facilitating peripheral interaction: design and evaluation of peripheral interaction for a gesture-based lighting control with multimodal feedback

Most interactions with today’s interfaces require a person’s full and focused attention. To alleviate the potential clutter of focal information, we investigated how interactions could be designed to take place in the background or periphery of attention. This paper explores whether gestural, multimodal interaction styles of an interactive light system allow for this. A study compared the performance of interactions with the light system in two conditions: the central condition in which participants interacted only with the light system, and the peripheral condition in which they interacted with the system while performing a high-attentional task simultaneously. Our study furthermore compared different feedback styles (visual, auditory, haptic, and a combination). Results indicated that especially for the combination feedback style, the interaction could take place without participants’ full visual attention, and performance did not significantly decrease in the peripheral condition. This seems to indicate that these interactions at least partly took place in their periphery of attention and that the multimodal feedback style aided this process.     

Positive display polarity is advantageous for both younger and older adults

The effect of display polarity on visual acuity and proofreading performance was investigated for younger and older adults. An advantage of positive polarity (dark characters on light background) over negative polarity (light characters on dark background) was expected for younger adults, but the effects on older adults were ambiguous. Light scatter due to residues in the senescent lens and vitreous humour could reverse the typical advantage of positive polarity. However, age-related changes lead to a decline in retinal illuminance. Brighter positive polarity displays should help to compensate for this decline and, accordingly, lead to better performance than darker negative polarity displays. Participants conducted a visual acuity test with black optotypes on white background or white optotypes on black background and performed a proofreading task in the same polarity. A positive polarity advantage was found for both age groups. The presentation in positive polarity is recommended for all ages.

Practitioner summary: In an ageing society, age-related vision changes need to be considered when designing digital displays. Visual acuity testing and a proofreading task revealed a positive polarity advantage for younger and older adults. Dark characters on light background lead to better legibility and are strongly recommended independent of observer's age.     

Effects of task characteristics on unimanual and bimanual movement times

Fitts' law cannot be used to predict movement times (MTs) of bimanual tasks since no empirical relationships associating task difficulty and bimanual MT have been demonstrated yet. Development of a ‘bimanual task difficulty index’ has been challenged by the complex patterns of coordination involved in simultaneously performing two tasks, one with each hand, under a control system with limited visual and attentional resources. To address this fundamental issue in human motor performance, bimanual object transfers with the left and right hands to targets of various precision requirements and separated by different distances were studied in six healthy subjects. Visual resource allocation during task performance was used to identify ‘primary’ and ‘secondary’ hand movements in bimanual tasks. While the primary movement was similar to a unimanual movement, the secondary MT varied with its own, as well as the contralateral hand's task constraints. These results, which were stable and consistent across six subjects, provide preliminary evidence that visual behaviour, indicating closed-loop control, can be used to systematically derive bimanual MTs.

Practitioner summary: A simple extension of Fitts' law cannot be used to predict movement times (MTs) of bimanual tasks since there is no consensus on the definition of a ‘bimanual task difficulty index’ in the literature. In this paper, we have approached this problem by using visual resource allocation patterns to systematically derive bimanual MTs.     

Content and representation effects with reasoning tasks in PROLOG form

Abstract

Two experiments were carried out to examine human reasoning performance in the context of the logic programming language PROLOG. Two factors, ‘content’ (familiar versus unfamiliar) and ‘representation’ (diagrammatic versus PROLOG-like list) were investigated. Subjects answered questions about hierarchical relationships in each condition. A significant interaction was obtained in both experiments, subjects making fewer errors in the familiar-diagram and unfamiliar-list conditions than in the familiar-list and unfamiliar-diagram conditions.

It is hypothesized that a lower percentage of correct responses was given in familiar-list and unfamiliar–diagram conditions because the representation of information prevented successful use of an appropriate reasoning strategy. Working memory limitations provide a basis for understanding constraints on reasoning strategies for solving task questions. These strategies may involve either a serial or a spatial solution process. One strategy may require a larger working memory load than another, depending on the representation and content of the task information. Implications for PROLOG programming instruction are discussed.     

Robotic execution of everyday tasks by means of external vision/force control

In this article, we present an integrated manipulation framework for a service robot, that allows to interact with articulated objects at home environments through the coupling of vision and force modalities. We consider a robot which is observing simultaneously his hand and the object to manipulate, by using an external camera (i.e. robot head). Task-oriented grasping algorithms (Proc of IEEE Int Conf on robotics and automation, pp 1794–1799, 2007) are used in order to plan a suitable grasp on the object according to the task to perform. A new vision/force coupling approach (Int Conf on advanced robotics, 2007), based on external control, is used in order to, first, guide the robot hand towards the grasp position and, second, perform the task taking into account external forces. The coupling between these two complementary sensor modalities provides the robot with robustness against uncertainties in models and positioning. A position-based visual servoing control law has been designed in order to continuously align the robot hand with respect to the object that is being manipulated, independently of camera position. This allows to freely move the camera while the task is being executed and makes this approach amenable to be integrated in current humanoid robots without the need of hand-eye calibration. Experimental results on a real robot interacting with different kind of doors are presented.     

Visual search in vibration environments: Effects of spatial ability,stimulus size and stimulus density

Visual search is one type of common encountered human-computer interaction tasks, but it has less been examined in vibration environments. The aim of this study was to examine the effects of one user characteristic (spatial ability) and two stimulus characteristics (i.e., stimulus size and stimulus density) on visual search performance during single- and double-target tasks in simulated vibration environments. Twenty-four participants attended an experiment where they were instructed to perform single- and double-target visual search tasks with varied levels of stimulus size and stimulus density under static, slight and moderate vibration environments, respectively. Results indicated that the two vibration conditions achieved comparable visual search performance, perceived visual fatigue, and perceived comfort with static condition across task types. Stimuli size and stimulus density yielded significant effects on visual search time in both single- and double-target tasks (p's < 0.001). Participants with high spatial ability were faster than those with low spatial ability in double-target tasks (p = 0.042). Users preferred interface design with medium-to-large stimulus size and low-to-medium stimulus density in visual search.     

Mechanisms of vibration-induced interference with manual control performance

Abstract

An experiment is described in which eight subjects performed three simple tasks (A, B and C) in static conditions and during exposure to whole-body vertical (z-axis) vibration at 0-5 and 40 Hz, at an acceleration magnitude of 2-1 ms^-2 r.m.s. All subjects performed all conditions with and without an arm support. The objective was to explore the mechanisms that may cause disruption of manual control performance during vibration exposure. With task A subjects simply held a control with no visual feedback of activity at the control. With task B, subjects used the control to hold a controlled element stationary on a display. Task C was the same as task B, except that subjects had improved visual feedback of movement of the controlled element. Results showed that both 0-5 and 40 Hz vibration caused significant increases in control activity at frequencies of up to about 1 Hz compared with the condition without vibration. With visual feedback in task C, subjects were able to detect drifting of the controlled element on the display and introduced compensatory control activity at frequencies above about 0 2 Hz. The arm support reduced the magnitude of vibration transmitted to the control at 4-0 Hz, but did not otherwise change the results.     

Effects of feedback type and modality on motor skill learning and retention

ABSTRACT

Two types of feedback, including knowledge of results (KR) and knowledge of performance (KP) are typically delivered as part of motor training using different sensory modalities. Twenty-four right-handed individuals performed a computer-based psychomotor training task using a contemporary haptic interface. Results revealed that KP was superior to KR for overall task performance retention, whereas KR was good for training specific aspects of performance. A combination of KP and KR through the same modality did not produce an additive positive learning effect for task performance. Auditory and haptic feedback improved retention over visual, but only with the use of multiple information cues. Design guidelines are provided for training systems for motor skill development and/or rehabilitation.     

Influence of computer feedback on attentional biases to emotional faces in children

We examined which type of corrective feedback in a computerized task produces an optimal balance between performance and emotional reactions in children. To that end, we conducted an emotional dot-probe task. We employed three types of corrective feedback (negative, positive, or mixed) along with a control, non-feedback condition. We tested the effect of feedback on: (i) task performance; (ii) immediate emotional reactions in terms of attentional preferences toward emotional faces (happy, sad, and angry); and (iii) self-reported affective experience after the task. Results showed that children committed more errors in the non-feedback group than in the mixed and negative feedback groups. Furthermore, the mixed feedback and the positive feedback groups showed an attentional bias away from sad faces. In contrast, the negative feedback group showed an attentional bias toward angry faces and felt unhappy after the task. Thus, the preferred type of feedback in children, in terms of better performance and a positive emotional reaction in a computerized task, is mixed feedback.     

This month Prophecies and ergonomic realities

Abstract

Texting on a cell phone disrupts walkers’ gait performance. The performance decrement has been attributed to increased motor demand, decreased visual information and increased cognitive load. However, relative contributions of motor, visual and cognitive factors are poorly understood. Here we quantitatively estimated the relative contributions of these factors by comparing multiple walking conditions. Thirty-two adults walked for 20 m, with or without a dual task on the phone. The dual task was either a cognitively demanding digit ordering task or a casual tapping task. Gait performance was assessed using gait speed, stride length, stride time and stride time variability. Results showed that texting negatively impacted gait performance. Importantly, we found that cognitive factor contributed the most, visual factor the least, and motor factor in between. Our findings resolve the inconsistency in the literature and unambiguously show that motor, visual and cognitive factors caused by simultaneous phone use all contribute to gait alterations.

Practitioner Summary: Walking performance is typically worsened when a concurrent phone use task such as texting is performed. We found that visual, motor and cognitive factors contributed to this performance decrement with increasing importance. Besides resolving inconsistency among previous reports, we also raised theoretical and practical concerns for phone use during walking.     

Environmental support hypothesis in designing multimedia training for older adults: Is less always more?

This study explores younger and older adults learning of MS Publisher functionalities from a multimedia tutorial. Twenty younger and twenty three older adults assigned to a redundant (experimental) or non-redundant (control) condition were taught how to create a greeting card, while the results of their learning were assessed with immediate and delayed performance measures. While younger learners benefited from a non-redundant condition, older learners exhibited an opposite trend. Redundant condition was beneficial for their performance efficiency on a set of a transfer tasks, and their troubleshooting performance during the delayed session. From a cognitive load perspective, using a redundant text along with an audio narration overloads learner’s working memory by placing more strain on the visual pathway and not providing any additional cognitive advantage. From an environmental support standpoint and decreased processing resources view of cognitive aging, providing additional representational support helps reducing the task demands for older adults and results in better learning. The results have cognitive and practical implications for the design of multimedia learning environments for older adults.