This paper examines the use of touchscreen smartphones, focusing on physical access. Using interviews and observations, we found that participants with dexterity impairment considered a smartphone both useful and usable, but tablet devices offer several important advantages. Cost is a major barrier to adoption. We describe usability problems that are not addressed by existing accessibility options, and observe that the dexterity demands of important accessibility features made them unusable for many participants. Despite participants' enthusiasm for both smartphones and tablet devices, their potential is not yet fully realized for this population.

Pinching and spreading gestures are prevalent in mobile applications today, but these gestures have not yet been studied extensively. We conducted an exploratory study of pinch and spread gestures with seated participants on a phone and a tablet device. We found device orientation did not have a significant effect on gesture performance, most pinch and spread tasks were completed in a single action, and they were executed in 0.9-1.2 seconds. We also report how participants chose to sit with the mobile device, variations in gesture execution method, and the effect of varying target width and gesture size. Our task execution times for different gesture distances and precision levels display a surprisingly good fit to a simple Fitts's Law model. We conclude with recommendations for future studies.

We examine three biometric authentication modalities -- voice, face and gesture -- as well as password entry, on a mobile device, to explore the relative demands on user time, effort, error and task disruption. Our laboratory study provided observations of user actions, strategies, and reactions to the authentication methods. Face and voice biometrics conditions were faster than password entry. Speaking a PIN was the fastest for biometric sample entry, but short-term memory recall was better in the face verification condition. None of the authentication conditions were considered very usable. In conditions that combined two biometric entry methods, the time to acquire the biometric samples was shorter than if acquired separately but they were very unpopular and had high memory task error rates. These quantitative results demonstrate cognitive and motor differences between biometric authentication modalities, and inform policy decisions in selecting authentication methods.

In this study, we explore the role of age and fluid intelligence on the behavior of people looking for information in a real-world search space. Analyses of mouse moves, clicks, and eye movements provide a window into possible differences in both task strategy and performance, and allow us to begin to separate the influence of age from the correlated but isolable influence of cognitive ability. We found little evidence of differences in strategy between younger and older participants matched on fluid intelligence. Both performance and strategy differences were found between older participants having higher versus lower fluid intelligence, however, suggesting that cognitive factors, rather than age per se, exert the dominant influence. This underscores the importance of measuring and controlling for cognitive abilities in studies involving older adults.

Information Foraging Theory (IFT) has established itself as an important theory to explain how people seek information, but most work has focused more on the theory itself than on how best to apply it. In this paper, we investigate how to apply a reactive variant of IFT (Reactive IFT) to design IFT-based tools, with a special focus on such tools for ill-structured problems. Toward this end, we designed and implemented a variety of recommender algorithms to empirically investigate how to help people with the ill-structured problem of finding where to look for information while debugging source code. We varied the algorithms based on scent type supported (words alone vs. words + code structure), and based on use of foraging momentum to estimate rapidity of foragers' goal changes. Our empirical results showed that (1) using both words and code structure significantly improved the ability of the algorithms to recommend where software developers should look for information; (2) participants used recommendations to discover new places in the code and also as shortcuts to navigate to known places; and (3) low-momentum recommendations were significantly more useful than high-momentum recommendations, suggesting rapid and numerous goal changes in this type of setting. Overall, our contributions include two new recommendation algorithms, empirical evidence about when and why participants found IFT-based recommendations useful, and implications for the design of tools based on Reactive IFT.

This study focuses on the use of web accessibility software by people with cerebral palsy performing three typical user tasks. We evaluate the customization options in the IBM accessibility Works add-on to the Mozilla Firefox browser, as used by ten users. While specific features provide significant benefit, we find that users tend to pick unnecessary options, resulting in a potentially negative user experience.

Sketching facilitates design in the exploration of ideas about concrete objects and abstractions. In fact, throughout the software engineering process when grappling with new ideas, people reach for a pen and start sketching. While pen and paper work well, digital media can provide additional features to benefit the sketcher. Digital support will only be successful, however, if it does not detract from the core sketching experience. Based on research that defines characteristics of sketches and sketching, this paper offers three preliminary tool examples. Each example is intended to enable sketching while maintaining its characteristic experience.

Designers often have no access to individuals who use screen reading software, and may have little understanding of how their design choices impact these users. We explore here whether cog-nitive models of auditory interaction could provide insight into screen reader usability. By comparing human data with a tool-generated model of a practiced task performed using a screen reader, we identify several requirements for such models and tools. Most important is the need to represent parallel execution of hearing with thinking and acting. Rules for placement of cogni-tive operators that were developed for visual user interfaces may not be applicable in the auditory domain. Other mismatches be-tween the data and the model were attributed to the extremely fast listening rate and differences between the typing patterns of screen reader usage and the model's assumptions. This work in-forms the development of more accurate models of auditory inter-action. Tools incorporating such models could help designers create user interfaces that are well tuned for screen reader users, without the need for modeling expertise.

Information foraging models have predicted the navigation paths of people browsing the web and (more recently) of programmers while debugging, but these models do not explicitly model users' goals evolving over time. We present a new information foraging model called PFIS2 that does model information seeking with potentially evolving goals. We then evaluated variants of this model in a field study that analyzed programmers' daily navigations over a seven-month period. Our results were that PFIS2 predicted users' navigation remarkably well, even though the goals of navigation, and even the information landscape itself, were changing markedly during the pursuit of information.