One Hand or Two Hands?
The first big question to ask is, Do users need one hand or two hands to operate a device? Interacting with Web sites on a computer normally requires the use of two hands when typing on a standard keyboard and one hand when using a mouse or other pointing device. With the vast diversity of handheld devices, users often need to decide whether to use a particular device with both hands or only one hand. Sometimes this decision is contextually constrained. For example, people driving a vehicle have only one hand free when operating a GPS device. Sometimes this decision is culturally constrained. For example, smartphone users in Japan are accustomed to using their smartphones with one hand, because they’re often using their other hand to hold onto a handrail on a running train.
Whether we intend a device for one-hand or two-hand use can greatly impact how we design it—and, therefore, affect how people perceive its usability. Usability professionals should take this factor into consideration when planning test tasks and creating test scenarios.
A Standard Keyboard or Different Button Sets?
When users interact with Web sites on a computer, a standard QWERTY keyboard provides a consistent mode of interaction with which they are familiar. However, when interacting with handheld devices, users may need to operate each particular device either by using hard controls such as buttons or by manipulating controls directly on a touchscreen. Handheld devices come in many different shapes, with many different types of controls. For example, the Sony Reader and Amazon Kindle 2 have very different button sets. The Sony Reader features 10 number buttons, a five-way control, a home button, a back button, a read button, and a zoom button. The Kindle 2 has a QWERTY keyboard, previous and next page buttons, a five-way control, a menu button, a home button, and a back button. Although both companies designed their devices to provide a better reading experience for users, their designers certainly had different ideas of how users should interact with a digital reading device. Five-way controls make it easy to navigate up, down, left, and right. A QWERTY keypad makes it easier to type.
Lack of standardization adds to the frustration users sometimes experience when interacting with handheld devices of different types. Because of this lack of standardization, usability professionals must think of usability for handheld devices systematically rather than focusing only on individual buttons. Thus, while answering such questions as Do users understand how to use this particular button? could be informative, it might be even more beneficial to ask questions like Does a particular device’s entire button set facilitate the tasks users most frequently carry out with the device? and Can users successfully find their way around the device, or do they get lost in the set of buttons?