Mobile User Experience

User experience (UX) research studies the complete relationship between products and users. It adds affective effects to usability, which ranges from short term user satisfaction with a single product to long lasting perception of a product line. My research in UX focuses on mobile products, smartphone applications, touch screen dashboards and web apps. It spans developing new interactions for mobile interfaces, mobile user interface design, mobile development and mobile user interface evaluation.

Challenges

Comparing user centered design for traditional desktop applications with mobile applications, design, development and evaluation are exasperated by many aspects of mobile application usability and functionality. Mobile user interface design is challenged by more than the obvious design concerns due to small screen real estate and broad pointing devices. Mobile UX designers cannot assume a typical device or ignore the context of their use because of the ubiquitous usage and proliferations of mobile devices. In addition, the UX designer cannot assume that their products will be used in isolation or in an insulated room. Mobile users will use products while outdoors and with other applications and devices. A mobile application typically accomplishes a small portion of the user's goals during their daily activities. The design and usability of mobile applications requires greater understanding of the complete context of the application usage, including the environment, and other actives.

Comparing usability evaluation for traditional desktop applications with mobile applications, the UX evaluator is frustrated by many dimensions of testing. Mobile interface testing is frustrated by more than the obvious challenges of observing user gesturing on small devices while performing tasks. Mobile UX evaluators are not satisfied with tracking just the user's eyes while using a single application; UX evaluators track users interacting with a multitude of applications through the user's environment while the user perform their daily activities. Tracking users extends beyond the moment and context use of a single application; the UX evaluator needs to track the user's perception before the product is released and their satisfaction through years of product use. Mobile user interface design requires evaluating the total usage of application through the environment and time.

Solutions

Mobile devices have extended and made more meaningful a variety of user interactions. Gesturing with fingers is more meaningful then with a mouse on mobile devices. The application can use the onboard GPS, camera and microphone to determine the user activity and environment. Photographing the environment or object can be part of the interaction that the application uses to eventually inform the user. The application can use vibrations to notify the user or to provide additional dimensions to other user interactions. Wi-Fi, Bluetooth and near field can extend the devices and sensors available to mobile applications. In general, mobile platforms offer a vaster and richer array of interactions then the desktop platforms.

Standard design and evaluation tools can be extended to UX. For example task analysis and even the more formal GOMS analysis can be extend to outline more than the user goals, tasks and operations on the device. Task analysis can relate the goals of the applications to the greater goal of the users in their lives. The analyses can predict the frequency of application usage and the relationship of the new application with other applications that the user interface with.

Although UX evaluator must contend with the invisibleness of many interactions on mobile devices, UX evaluator can take advantage of many of the onboard devices to infer some interaction details and extend their observations. The same sensors on the mobile device that extend the interaction techniques can also be used to infer the user's environment and track the user through the environment. Although eye tracking may be impossible while using a mobile device, users attentions can be inferred from touch and gesture responses. The user facing camera on the device can be used to capture facial expressions and affective response.

Research

My research began with a focus on developing gesturing interaction and modelling pointing effectiveness. The pointing models explored extending Fitts's law to blunt pointers such as fingers and precise pointing with a mouse. The models informed the design of new pointing devices such as gravity mouse, and the combined mouse and scroll wheel precise pointing. My current research focuses on mobile usability, and designing new mobile applications and interactions.

Computer Science and Human Factors graduate students interested in mobile application design, usability and evaluations for their dissertation or thesis should contact me. We can discuss your interests and research opportunities in more detail.

Publications

• Gao, C., Pastel, R., and Tan, J. (2013) An Experimental Study of a New Channel for Data Input On Small Mobile Devices. Journal on Knowledge and Data Engineering.
• Pastel, R, (2012) Precise Positioning on Computer Monitors: Comparison of Mouse and Scroll Wheel in One dimension, Proceedings of Human Factors and Ergonomics Society (HFES 2012) p. 1248-1242.
• Gao, C., Pastel, R. and Tan, J. (2012) TiltClick: One-Handed Eyes-Free Numeric and Symbol Input for Calculator Applications, Proceeding IEEE International Virtual Environments, Human-Computer Interfaces, and Measurement Systems 2012, p. 30-33.
• Pastel, R, (2010) Positioning Graphical Objects on Computer Screens: a Three-Phase Model, Human Factors, vol. 53, No. 1, pp. 23-37.
• Pastel, R. and Ward, P. (2011) Modeling the Orientation of Graphical Objects on Computer Displays Using Indented Mouse Wheels, Proceedings of Human Factors and Ergonomics Society (HFES 2011) p. 510-514.
• Gao, C., Pastel, R. and Tan, J. (2010) Yet Another User Input Method: Accelerometer Assisted Single Key Input, in Proceedings of World Congress on Intelligent Control and Automation (WCICA 2010), 3949-3954.
• Pastel, R, (2009) Investigating the Difficulty of One Degree of Freedom Positioning: Associating Movement Phases with Regions, Proceedings of Human Factors and Ergonomics Society (HFES 2009), pp. 965-969.
• Pastel, R. (2009) Modeling the Difficulty for Centering Rectangles in One and Two Dimensions, Proceedings of Human Computer Interaction International (HCII'09), 879-888, Human-Computer Interaction. Novel Interaction Methods and Techniques, 13th International Conference, HCI International 2009, San Diego, CA, USA, July 19-24, 2009, Proceedings, Part II Book Series Lecture Notes in Computer Science (LNCS), Publisher Springer Berlin / Heidelberg.
• Pastel, R. (2008) The Difficulty of Centering Circular Discs, Proceedings of Human Factors and Ergonomics Society (HFES 2008), Computer Systems Technical Group, New York, NY, September 22-26.
• Pastel, R., Himes, P., Harper, M., and Helton, W. (2007) Gravity Mouse Design and Evaluation: Effects of Distracters and Target Size, Proceedings of Human Factors and Ergonomics Society 2007, Computer Systems Technical Group, Baltimore MD, October 1-5, 2007, pp. 444-448.
• Pastel, R., Champlin, J., Harper, M., Paul, N., Helton, W., Schedlbauer, M. and Heines, J., (2007) The Difficulty of Remotely Negotiating Corners, Proceedings of Human Factors and Ergonomics Society 2007, Computer Systems Technical Group, Baltimore MD, October 1-5, 2007, pp. 489- 493.
• Schedlbauer, M.,and Pastel, R., (2007) A Tool for Enabling Scientific Exploration of Human Performance Models in HCI Education. In Proceedings of HCI Educators 2007, Aveiro, Portugal, March, 2007, pp. 116-121.
• Schedlbauer, M., Pastel, R. and Heines, J. (2006) Effects of Posture on Target Acquisition with a Trackball and Touch Screen, Proceedings of International Conference on Information Technology Interfaces (ITI'06), June 2006, Dubrovnik, Croatia. Awarded best student paper.
• Pastel, R. and Skalsky, N. (2004) Object-Action Association: A HCI Design Model, International Conference on Intelligent User Interfaces (IUI'04), p. 295-7, Madeira, Portugal, Jan. 13-16, 2004.
• Skalsky, N. and Pastel, R. (2004) Transportable Research Instrument: a PDA-based Laboratory for Science Experiments, IEEE International Workshop on Wireless and Mobile Technologies in Education (IEEE WMTE'04), Jhongli, Taiwan, March 23-24, 2004.