Many interactive systems can be accessed across a range of different platforms, enabling cross-platform services and allowing users to migrate their tasks from one platform to another. Despite the increased worldwide use of cross-platform services, there is limited research into (1) how cross-platform usability can be assessed, (2) key, culture-related, and context-related user experiences (UXs) of multiple interactive systems across different platforms, (3) user interaction behavioural patterns when switching between devices and (4) the use of eye tracking for cross-platform usability evaluation. In this thesis, we present our findings from a set of studies designed to answer research questions addressing these four areas. We used think-aloud protocol, observation, questionnaires and eye tracking to gather data.
We defined cross-platform usability and developed a model for assessing it. In the first user study, we investigated our model for assessing cross-platform usability, the key cross-platform UX elements and the user interaction behavioural patterns over three cross-platform services. Our analysis showed that our model is valuable for assessing and quantifying cross-platform usability. We also identified a set of cross-platform UX elements (e.g., consistency and fluency) and user interaction behavioural patterns (e.g., habituation).
In the second user study, we investigated cross-platform cross-cultural UX. Forty students volunteered to participate in this study. Participants were from nine different countries. Our analysis identified a set of objective and subjective cultural factors that most influence cross-platform UX. The objective factors are service related (e.g., direction and translation) and device related (typing interface design). The subjective factors are power–distance (PD) and uncertainty–avoidance (UA).
In the third user study, we investigated cross-platform cross-context UX. Forty-five participants performed tasks on five cross-platform services across different contexts. Participants were divided into ten different groups. Five participant groups switched between interfaces across devices in a seated–moving contextual setting. The other five participant groups attempted their tasks using services in a seated setting. Our study findings showed that testing cross-platform UX in the seated–moving settings generated more issues (e.g., more consistency problems). Another outcome of this study was that users reported several UX design issues associated with mobile UIs operating while walking. We analysed the issues and proposed UX design principles (e.g., reduction and aesthetic simplicity) for mobile UIs in moving situations.
Our fourth user study sought a relationship between eye-tracking metrics and cross-platform usability problems. We user tested three cross-platform services and identified a set of usability problems. We separated the identified problems into traditional and cross-platform usability problems. Some of the cross-platform usability problems were associated with user eye-tracking patterns (ETPs). We recommend some considerations for evaluators to use as indicators when predicting possible cross-platform usability problems.
In our final study for this research, we conducted a survey of eight professionals specialising in UX to seek their opinions about our developed cross-platform usability assessment model and UX design framework. The model and framework were finalised, incorporating results from all of our previous user studies. Overall, UX experts assessed the model and the framework as appropriate and useful.