Last year was the first time that mobile users topped desktop users on a worldwide scale. If we take a look at the global statistics the leading screen resolution today is 640x360 with over 22%.
This shouldn’t be ignored and while responsive and mobile first development have been around for some time now, interaction in a mobile interface is very different to one in a desktop interface. With the rise of React Native and Progressive Web Apps developing mobile user interfaces will also be a big part of Web Development in the coming years.
When developing mobile user interfaces, simplicity is essential for a good user experience. The interface should be consistent, avoid cognitive overload and disorientation in the user.
In order to satisfy and measure users interactions, 5 measurable principles have been devised in this paper. This post will give a quick summary of these principles and look at some examples to outline aspects we should think about when creating mobile interfaces.
Effectiveness describes how effective a user is while using an interface. The user has previous experience from other interfaces and the real world. In Human Computer Interaction (HCI) this is called a mental model the user is creating in order to comprehend complex concepts easier. We can increase the users effectiveness by benefitting from his knowledge gained from the real world. The goal of effectiveness is to reduce the number of actions required to complete a task.
Efficiency describes in what way the user can comprehend the current state of the application and the operations that can be performed. It is measured in actions per second and describes how efficient the user is in completing a task.
Productivity describes how long a user takes to complete a task successfully. It also describes how easy it is for the user to spot and identify functionalities offered by an interface. It is measured in the number of actions needed to complete a task relative to time.
Giving the user feedback is one of the most important parts of interface design. With appropriate feedback errors can be reduced significantly. We can measure Error Safety by counting the number of errors committed in each action of each task.
Reducing cognitive load in the user is essential to making an interface feel nice to use. We can do this by using metaphors for difficult concepts and keeping the interface simple in order not to confuse the user. A way of measuring cognitive load is by counting the actions per view.
When we design an user interface the focus of it’s design should always lie on if the interface is helping the user to fullfill the task he wants to complete. Some questions to ask yourself during the design of any interface are:
Since mobile interfaces are very limited due to small screen sizes, it’s even more important to keep applications simple and focused on the tasks the user wants to complete. If the interface is getting too complex and confusing, it might be because it tries to fullfill to many diverse conditions and should actually be split in different applications. By keeping Effectiveness, Efficiency, Productivity, Error Safety and Cognitive Load in mind we can avoid building interfaces, that might look fancy but don’t actually support the user in his task completion.