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Current methods of evaluating essential tremor (ET) either rely on subjective ratings or use limited tremor metrics (i.e., severity/amplitude and frequency). In this study, we explored performance metrics from Fitts law tasks that replicate and expand existing tremor metrics, to enable low-cost, home-based tremor quantification and analyze the cursor movements of individuals using a 3D mouse while performing a collection of drawing tasks. We analyzed the 3D mouse cursor movements of 11 patients with ET and three controls, on three computer-based tasksa spiral navigation (SPN) task, a rectangular track navigation (RTN) task, and multi-directional tapping/clicking (MDT)with several performance metrics (i.e., outside area (OA), throughput (TP in Fitts law), path efficiency (PE), and completion time (CT)). Using an accelerometer and scores from the Essential Tremor Rating Assessment Scale (TETRAS), we correlated the proposed performance metrics with the baseline tremor metrics and found that the OA of the SPN and RTN tasks were strongly correlated with baseline tremor severity (R2=0.57 and R2=0.83). We also found that the TP in the MDT tasks were strongly correlated with tremor frequency (R2=0.70). In addition, as the OA of the SPN and RTN tasks was correlated with tremor severity and frequency, it may represent an independent metric that increases the dimensionality of the characterization of an individuals tremor. Thus, this pilot study of the analysis of those with ET-associated tremor performing Fitts law tasks demonstrates the feasibility of introducing a new tremor metric that can be expanded for repeatable multi-dimensional data analyses.

The present research featured the regularities, according to which the accuracy of human movements is associated with the length of these movements and time. The author considered the speed–accuracy tradeoff problem by analyzing the procedural aspect of cognitive performance. The experiment included more than a thousand participants and was performed on a portable touch screen device that tested the subject's attitude to solving problems in terms of speed or accuracy. The research objective was to identify significantly different ways of solving the speed–accuracy tradeoff dilemma. At the fine motor level, the participants failed to accomplish a one-to-one correspondence between target area and target time. This ambiguity was a manifestation of various cognitive strategies for performing a speed–accuracy tradeoff task. The Fitts law violations were determined using a wide range of statistical methods and manifested themselves at the level of criteria analysis for the normality of data distribution, types of variance analysis, and multivariate data analysis. The cluster analysis could register various strategies for performing the speed–accuracy tradeoff task. Additional variables, e.g. professional status of the subjects, made it possible to interpret the differences according to specific skills in solving cognitive tasks and to clarify the nature of these skills.

The trade-off between speed and accuracy in precision tasks is important to evaluate during user interaction with input devices. When different sensory cues are added or altered in such interactions, those cues have an effect on this trade-off, and thus, they affect overall user performance. For instance, adding cues like haptic feedback and stereoscopic viewing will result in more realistic user interaction, thus improving performance in these tasks. Also, adding a noticeable disparity between physical and virtual movements creates a mismatch between visual and proprioceptive systems, which generally has a negative effect on performance. In this study, we investigate the effects of haptic feedback, stereoscopic viewing, and visuo-proprioceptive mismatch on how quickly and accurately users complete a virtual pick-and-place task using the PHANToM OMNI. Through this experiment, we find that in the movement phase of a ring transfer, movement time and user performance are affected by haptic feedback and visuo-proprioceptive mismatch, and the main effects of stereoscopic viewing appears to be limited to the more precise step when the ring is around the target peg.

Effective teaching of concepts related to human computer interaction (HCI) requires introduction of the core paradigms as well as the design and evaluation methodologies to the learners. In this pa...

There are circumstances in which humans are required to move in environments wherein accuracy should be maximized, such as golf putting or surgeons’ hand movements during surgical procedures. Fitts’ law expresses human movement by movement time and task difficulty, which is determined by one's distance from the target and the targets’ size. Additionally, this law is considered as the most universal expression of human movement. However, it is calculated based on the possibility of failure, mainly because a tap error ratio of ~4% occurred in the continuous tap task used by Fitts. Thus, this study aimed to examine how movement changes can occur with an error rate of 0%, and whether Fitts’ law can be applied to human movement in such a setting. The continuous tap task was performed under two conditions: a conventional one, and a new condition where the devised error rate becomes 0%. To measure movement change during tapping, the variation of the entire trajectory was quantified by principal component analysis, and changes in the quantified values of the trajectory toward the target were examined. For the new condition, no tapping errors occurred; the quantified value of the trajectory toward the target decreased compared with the conventional condition. It was considered that this related to the process of feedback control, and that this process related to an increase in movement time per tap. We suggest that increased information processing may account for these changes. Furthermore, the Fitts’ law model, shown from the regression lines for movement time and difficulty, displayed a high fit for both conditions. However, it was difficult to evaluate movement time with the highest index of difficulty for the new condition using the model for the conventional condition. Therefore, we conclude that the conventional model may need to be modified for conditions where the error rate is 0%.

A central account of cognitive aging is the dedifferentiation among functions due to reduced processing resources. Previous reports contrasting trends of aging across cognitive domains mostly relied on transformed scores of heterogeneous measures. By quantifying the computational load with information entropy in tasks probing motor and executive functions, this study uncovered interaction among age, task, and load as well as associations among the parametric estimates of these factors at the individual level. Specifically, the linear functions between computational load and performance time differed significantly between motor and executive tasks in the young group but not in the elderly group and showed stronger associations for parameters within and between tasks in the elderly group than in the young group. These findings are in line with the dedifferentiation hypothesis of cognitive aging and provide a more principled approach in contrasting trends of cognitive aging across different domains from the information-theoretic perspective.

Design of applications requires proper management of content, interaction elements and space. In web systems flow of interactions is often based on attention catching components in a form of elements of navigation or advertising content. Distance from central part of interface is affecting user behavior, what can be overcome by scaling size of the objects within the interface according to Fitts’s law. Here we examine the effects of flickering elements with different frequency, direction and distance from central elements of webpage on user attention and habituation reduction. The aim of the study was to examine how to overcome users’ resistance to stimuli based on objects flickering with different frequencies located in different directions and distances. We wanted to check if the higher flicker frequency can compensate the larger distance and increase and user focus depending on whether the element is located nearest or farthest, similarly like objects sizes for Fitts’s law. Results showed that flicker increases the attention to objects with higher distance but has no effect on nearest objects. I was possible to improve total time attracted by distance objects by twenty percent, however the higher performance was observed to nearest objects, no matter what frequency was used for them.

The target in an augmented reality (AR) interface is often located in the distance and outside the initial AR viewport, requiring the user to rotate the AR device, instead of translating it, to complete the search and selection of the target. In order to quantitatively analyze rotating the AR device in the AR interface in the selection of a target located outside the initial visual window, we propose and experimentally verify a quantitative model based on angle measurement under two selection techniques: with and without cursor. The results show that the model proposed in this paper can accurately describe the interactive process when a rotating AR device completes the target selection task. With cursor angle measurement achieves a model fitting value of R2 = 0.937, and without cursor angle measurement achieves a model fitting value of R2 = 0.915; hence, good modeling of user performance in AR selection tasks is achieved.

The mouse, being the major means of inputting and controlling data on a computer, should be set right for best performance. Mouse gain, defined as the ratio of the movement distance on the computer screen to the movement distance of the mouse, controls the movement time when both speed and accuracy are important. Reported optimum gain values vary widely from about 2 to 15. An experiment having a targeting task was used to test 16 participants using a wide range of gain (1.2, 2.4, 14.5, and 38.9). An optimum gain of 2.4 was found for a display movement amplitude ( A ) of 100 mm, whereas the optimum gain was 14.5 for amplitudes of 200 and 400 mm. Depending on the gain and the movement amplitude, Fitts’ law should be modified to accurately model movement time (MT) in the form of MT = A + b (ID) − c ( A *ID). Only at low gains could a critical index of difficulty be determined, that being about 3.5.

Understanding the endpoint distribution of pointing selection tasks can reveal the underlying patterns on how users tend to acquire a target, which is one of the most essential and pervasive tasks in interactive systems. It could further aid designers to create new graphical user interfaces and interaction techniques that are optimized for accuracy, efficiency, and ease of use. Previous research has explored the modeling of endpoint distribution outside of virtual reality (VR) systems that have shown to be useful in predicting selection accuracy and guide the design of new interactive techniques. This work aims at developing an endpoint distribution of selection tasks for VR systems which has resulted in EDModel , a novel model that can be used to predict endpoint distribution of pointing selection tasks in VR environments. The development of EDModel is based on two users studies that have explored how factors such as target size, movement amplitude, and target depth affect the endpoint distribution. The model is built from the collected data and its generalizability is subsequently tested in complex scenarios with more relaxed conditions. Three applications of EDModel inspired by previous research are evaluated to show the broad applicability and usefulness of the model: correcting the bias in Fitts's law, predicting selection accuracy, and enhancing pointing selection techniques. Overall, EDModel can achieve high prediction accuracy and can be adapted to different types of applications in VR.

Previous research on performance on the Fitts pointing task has identified the relative influences of task and effector constraints. Effector constraints are those specific to the motor and physical aspects of the task, such as movement distance, which tend to affect the overall duration of the movement. Task constraints, such as target size, affect the underlying movement dynamic, with effects isolated to the end of the movement, causing asymmetry in the velocity profile. Here, evidence confirming these effects is reported, along with a new task constraint, target size as defined as a physical constraint on final positioning error. A new formulation of Fitts’ law is presented that accounts for all constraints.

Recent studies examining children diagnosed with Autism Spectrum Disorder (ASD) have revealed kinematic markers highlighting deficits in the preparatory and online phases of upper extremity movements. In the following study, 12 children with high functioning ASD were first assessed (pre-test) on 15 trials of a reciprocal upper extremity Fitts Law target task by flexing and extending their right arm in the horizontal plane between two targets as fast and accurately as possible. Following the initial assessment, the children either continued with 30 additional trials of the target task (control) or were asked to track a sine wave template (experimental). All participants were then assessed on 15 trials of the target test (post-test). Results reveal that tracking the sine wave template during training not only produced faster movements compared to the control but also produced these movements in a more harmonic way.

The time T needed to reach a target of width W located at distance D varies as a logarithmic or power function of the quotient of D/W. The received, strong version of Fitts’ law requires isochrony—...

Night vision goggles (NVGs) enable aircrew to complete missions in the cover of night, but dramatically increase and alter the distribution of mass borne by the head. Our novel approach to visual target acquisition, based on Fitts’ Law, was used to assess differences across three different performance metrics between low (L) and high (H) head supported mass (HSM) conditions. Fifteen healthy male participants completed time-optimal and reciprocal visual target acquisitions between target pairs arranged in four different movement trajectories. A significant interaction effect was found and subsequent post hoc analysis revealed that participants required more time to acquire the 20 mm target in the H-HSM condition. In the H-HSM condition participants had a higher error index during target acquisition and required more time to move off the target. Our approach demonstrates great promise in distinguishing performance decrements associated with the use of helmeted systems that include NVGs.

Previous research suggests that using Fitts' law; attentional focus or challenge point framework (CPF) is beneficial in balance control studies. A scoping review was conducted to examine studies that utilized these motor behavior concepts during balance control tasks. An extensive literature search was performed up to January 2018. Two independent reviewers conducted a study selection process followed by data extraction of the search results. Forty-six studies were identified, with 2 studies related to CPF, 12 studies related to Fitts' law and 32 studies related to focus of attention. The CPF appears to be a useful method for designing a progressive therapeutic program. Fitts' law can be used as a tool for controlling the difficulty of motor tasks. Focus of attention studies indicate that adopting an external focus of attention improves task performance. Overall, studies included in this review report benefit when using the selected motor behavior concepts. However, the majority (>80%) of studies included in the review involved healthy populations, with only three clinical trials. In order to ascertain the benefits of the selected motor behavior concepts in clinical settings, future research should focus on using these concepts for clinical trials to examine balance control among people with balance impairments.

There is a long-held view that discrete movements aimed to a target are composed of a sequence of movement units (sub-movements) that have different roles in motor control (e.g., initial impulse, error correction and movement termination) depending on the task constraints (e.g., spatial-temporal requirements). Here we report findings from the manipulation of vision/no-vision on the prevalence and type of sub-movements in discrete movement tasks over a range of space-time task criteria. The presence of vison resulted in longer movement times compared to the no-vision counterpart in time-matching tasks. A similar vision effect was observed in the highest Index of Difficulty for time-minimization tasks. Conditions that resulted/required longer movement times demonstrated more pre-velocity-peak and post-velocity-peak types of sub-movements whereas short movement times increased the likelihood of overshooting sub-movements. The present study results are consistent with the idea that movement time is the variable associated with changes in sub-movement profiles. ispartof: JOURNAL OF MOTOR BEHAVIOR vol:54 issue:2 pages:173-185 ispartof: location:United States status: published

This study evaluates and compares the suitability for child–computer interaction (CCI, the branch within human–computer interaction focused on interactive computer systems for children) of two devices: a standard computer mouse and the ENLAZA interface, a head mouse that measures the user’s head posture using an inertial sensor. A multidirectional pointing task was used to assess the motor performance and the users’ ability to learn such a task. The evaluation was based on the interpretation of the metrics derived from Fitts’ law. Ten children aged between 6 and 8 participated in this study. Participants performed a series of pre- and post-training tests for both input devices. After the experiments, data were analyzed and statistically compared. The results show that Fitts’ law can be used to detect changes in the learning process and assess the level of psychomotor development (by comparing the performance of adults and children). In addition, meaningful differences between the fine motor control (hand) and the gross motor control (head) were found by comparing the results of the interaction using the two devices. These findings suggest that Fitts’ law metrics offer a reliable and objective way of measuring the progress of physical training or therapy.

In Eqs. (1-2), t is the pointing time, A is the amplitude (distance) to the target, W is the target size and a, b are constants that depend on experiment conditions. ID is larger as A is larger and/or W is smaller. Values of a and b in Eq. (1) are determined by sampling (A, W, t) data and applying the linear regression analysis to the data. Eq. (2) shows that ID values are the same for (A, W) and (nA, nW) where n > 0. This research is motivated by recent smart phones that employ touch UIs. Compared with other touch screen devices such as tablet PCs, mobile phones have smaller screens so that widgets on mobile phone screens are likely to be smaller. Widgets can be designed for devices with various screen sizes so that theoretical ID values in Eq. (2) are consistent among the devices: larger/smaller sizes & distances for larger/smaller screens. If ID in Eq. (2) is an appropriate index of actual pointing difficulty independently of screen sizes, users’ pointing performances on the same device are consistent among widget designs (A, W) and (nA, nW): note that a, b in Eq. (1) are constant (independent to ID) so that a, b must be the same for two data sets sampled with the two widget designs (A, W) and (nA, nW). The aim of this research is to investigate whether the above is true: appropriateness of the ID formulation in Eq. (2) is evaluated from the viewpoint of dependency on screen sizes, by experiments with participants. Limitations of Fitts’ law have been researched and extensions have been proposed. For example, an extension for 2D pointing tasks was proposed (MacKenzie & Buxton, 1992). Our research aims at investigating possible limitations on screen sizes. A related research was previously reported (Oehl et al., 2007). They investigated how display size influenced pointing performances on a touch UI and reported that in large displays a fast and comparably accurate execution was chosen in contrast to a very inaccurate and timeconsuming style in small displays. In their research the size of small screen was 6.5”, and only a large screen touch UI device was utilized for user experiments: screen sizes were

While a pinch action is gaining popularity for selection of virtual objects in eye-gaze-based systems, it is still unknown how well this method performs compared to other popular alternatives, e.g., a button click or a dwell action. To determine pinch’s performance in terms of execution time, error rate, and throughput, we implemented a Fitts’ law task in Virtual Reality (VR) where the subjects pointed with their (eye-)gaze and selected / activated the targets by pinch, clicking a button, or dwell. Results revealed that although pinch was slower, made more errors, and had less throughput compared to button clicks, none of these differences were significant. Dwell exhibited the least errors but was significantly slower and achieved less throughput compared to the other conditions. Based on these findings, we conclude that the pinch gesture is a reasonable alternative to button clicks for eye-gaze-based VR systems.