Modeling and predicting pointing errors in two dimensions

Recently, Wobbrock et al. (2008) derived a predictive model of pointing accuracy to complement Fitts ’ law’s predictive model of pointing speed. However, their model was based on one-dimensional (1-D) horizontal movement, while applications of such a model require two dimensions (2-D). In this paper, the pointing error model is investigated for 2-D pointing in a study of 21 participants performing a time-matching task on the ISO 9241-9 ring-of-circles layout. Results show that the pointing error model holds well in 2-D. If univariate endpoint deviation (SDx) is used, regressing on N=72 observed vs. predicted error rate points yields R 2 =.953. If bivariate endpoint deviation (SDx,y) is used, regression yields R 2 =.936. For both univariate and bivariate models, the magnitudes of observed and predicted error rates are comparable. Author Keywords: Pointing error model, Fitts ’ law, metronome, movement time, error prediction, error rates

Interactions under the desk: a characterisation of foot movements for input in a seated position

We characterise foot movements as input for seated users. First, we built unconstrained foot pointing performance models in a seated desktop setting using ISO 9241-9-compliant Fitts’s Law tasks. Second, we evaluated the effect of the foot and direction in one-dimensional tasks, finding no effect of the foot used, but a significant effect of the direction in which targets are distributed. Third, we compared one foot against two feet to control two variables, finding that while one foot is better suited for tasks with a spatial representation that matches its movement, there is little difference between the techniques when it does not. Fourth, we analysed the overhead caused by introducing a feet-controlled variable in a mouse task, finding the feet to be comparable to the scroll wheel. Our results show the feet are an effective method of enhancing our interaction with desktop systems and derive a series of design guidelines

Head movement assessment of cerebral palsy users with severe motor disorders when they control a computer thought eye movements

[Abstract] Eye tracking is currently a promising technology to access computers for people who suffer severe motor disorders, like cerebral palsy. However, there is a lack of usability assessment procedures and concrete value to describe the user’s motor capabilities in this specific scenario of computer control. This paper presents a methodology, based on two head movement assessment metrics and the ISO-9241, for the quantitative motor description of users with severe motor disorders, when they control the computer thought their eyes. Seven participants with CP and three people without motor disabilities were recruited for the evaluation of the proposed procedure. Results evidence for the first time how users with CP control their head while they access a computer with their eyes.Ministerio de Economía, Industria y Competitividad; RTC-2015-3967-1Ministerio de Economía, Industria y Competitividad; DPI2015-68664-C4-1-RMinisterio de Economía, Industria y Competitividad; RTC-2015-4327-

Characterizing the Effects of Local Latency on Aim Performance in First Person Shooters

Real-time games such as first-person shooters (FPS) are sensitive to even small amounts of lag. The effects of network latency have been studied, but less is known about local latency -- that is, the lag caused by local sources such as input devices, displays, and the application. While local latency is important to gamers, we do not know how it affects aiming performance and whether we can reduce its negative effects. To explore these issues, we tested local latency in a variety of real-world gaming systems and carried out a controlled study focusing on targeting and tracking activities in an FPS game with varying degrees of local latency. In addition, we tested the ability of a lag compensation technique (based on aim assistance) to mitigate the negative effects. To motivate the need for these studies, we also examined how aim in FPS differs from pointing in standard 2D tasks, showing significant differences in performance metrics. Our studies found local latencies in the real-world range from 23 to 243~ms that cause significant and substantial degradation in performance (even for latencies as low as 41~ms). The studies also showed that our compensation technique worked well, reducing the problems caused by lag in the case of targeting, and removing the problem altogether in the case of tracking. Our work shows that local latency is a real and substantial problem -- but game developers can mitigate the problem with appropriate compensation methods

In-Air Un-Instrumented Pointing Performance

I present an analysis of in-air un-instrumented pointing and selection. I look at the performance of these systems and how this performance can be improved, with the eventual goal that their throughput reaches that of the mouse. Many potential limiting factors were explored, such as latency, selection reliability, and elbow stabilization. I found that the un-instrumented in-air pointing as currently implemented performed significantly worse, at less than 75% of mouse throughput. Yet, my research shows that this value can potentially reach mouse-like levels with lower system latencies, user training, and potentially improved finger tracking. Even without these improvements, the large range of applications for un-instrumented 3D hand tracking makes this technology still an attractive option for user interfaces

Automatic Web Navigation Problem Detection Based on Client-Side Interaction Data

The current importance of digital competence makes it essential to enable people with disabilities to use digital devices and applications and to automatically adapt site interactions to their needs. Although most of the current adaptable solutions make use of predefined user profiles, automatic detection of user abilities and disabilities is the foundation for building adaptive systems. This work contributes to diminishing the digital divide for people with disabilities by detecting the web navigation problems of users with physical disabilities based on a two-step strategy. The system is based on web user interaction data collected by the RemoTest platform and a complete data mining process applied to the data. First, the device used for interaction is recognized, and then, the problems the user may be having while interacting with the computer are detected. Identification of the device being used and the problems being encountered will allow the most adequate adaptation to be deployed and thus make the navigation more accessible

Experimental Analysis of a Spatialised Audio Interface for People with Visual Impairments

Sound perception is a fundamental skill for many people with severe sight impairments. The research presented in this paper is part of an ongoing project with the aim to create a mobile guidance aid to help people with vision impairments find objects within an unknown indoor environment. This system requires an effective non-visual interface and uses bone-conduction headphones to transmit audio instructions to the user. It has been implemented and tested with spatialised audio cues, which convey the direction of a predefined target in 3D space. We present an in-depth evaluation of the audio interface with several experiments that involve a large number of participants, both blindfolded and with actual visual impairments, and analyse the pros and cons of our design choices. In addition to producing results comparable to the state-of-the-art, we found that Fitts’s Law (a predictive model for human movement) provides a suitable a metric that can be used to improve and refine the quality of the audio interface in future mobile navigation aids

Redirected Touching

In immersive virtual environments, virtual objects cannot be touched. One solution is to use passive haptics - physical props to which virtual objects are registered. The result is compelling; when a user reaches out with a virtual hand to touch a virtual object, her real hand touches and feels a real object. However, for every virtual object to be touched, there must be an analogous physical prop. In the limit, an entire real-world infrastructure would need to be built and changed whenever a virtual scene is changed. Virtual objects and passive haptics have historically been mapped one-to-one. I demonstrate that the mapping need not be one-to-one. One can make a single passive real object provide useful haptic feedback for many virtual objects by exploiting human perception. I developed and investigated three categories of such techniques: 1. Move the virtual world to align different virtual objects in turn with the same real object 2. Move a virtual object into alignment with a real object 3. Map real hand motion to different virtual hand motion, e.g., when the real hand traces a real object, the virtual hand traces a differently shaped virtual object. The first two techniques were investigated for feasibility, and the third was explored more deeply. The first technique (Redirected Passive Haptics) enables users to touch multiple instances of a virtual object, with haptic feedback provided by a single real object. The second technique (The Haptic Hand) attaches a larger-than-hand virtual user interface to the non-dominant hand, mapping the currently relevant part of the interface onto the palm. The third technique (Redirected Touching) warps virtual space to map many differently shaped virtual objects onto a single real object, introducing a discrepancy between real and virtual hand motions. Two studies investigated the technique's effect on task performance and its potential for use in aircraft cockpit procedures training. Users adapt rather quickly to real-virtual discrepancy, and after adaptation, users perform no worse with discrepant virtual objects than with one-to-one virtual objects. Redirected Touching shows promise for training and entertainment applications.Doctor of Philosoph