Interactions - September/October 2010

When users
think they did one
thing but actually did
something else, they
lose their sense of
controlling the
system because they
don’t understand

surface, or tilted at an angle? All varieties now exist.

Sensitive screens give many opportunities for accidental selection and the triggering of actions. This happens on small screens because the target items might be small and close together. This happens on large screens because the same hands necessary to hold and stabilize the device can accidentally touch the screen.

the connection between
actions and results.

Discoverability The true advantage of the Graphical User Interface (GUI) was that commands no longer had to be memorized. Instead, every possible action in the interface could be discovered through systematic exploration of the menus. Discoverability is another important principle that has now disappeared. Apple specifically recommends against the use of menus. The Android UI team takes the opposite position, even providing a dedicated menu key, but does not require that it always be active. Moreover, swipes and gestures cannot readily be incorporated in menus: So far, nobody has figured out how to inform the person using the app what the alternatives are.

September + October 2010

interactions

way the developer chooses, often to the distress of the poor person trying to use the system.

Some applications allow pinching to change image scale; others use plus and minus boxes. Some allow you to flip screens up, some down, some to the right, some to the left, and some not at all. Touching an image can enlarge it, hyperlink from it, flip it over, unlock it so it can be moved, or whatever the developer and his whim decided.

The different operating-sys-tem developers have provided detailed interface guidelines for their products. Unfortunately, the guidelines differ from one another, in part because different companies wish to protect their intellectual property by not allowing other companies to follow their methods. But whatever the reason, proprietary standards make life more difficult for everyone. For sure, they undermine the main way in which users learn from each other.

Scalability

Home computers, whether lap-top or desktop, always came with a wide variety of screen sizes. Now that computer operating systems are starting to support multitouch technology, this means gestures must work on large screens as well as small. There is a plethora of screen sizes for cell phones, including the emergence of an in-between form; we now have midsize screens. Eventually, screens will range from tiny to huge, conceivably wall-size (or at least, whiteboard-size). However, gestures that work well for small screens fail for large ones, and vice versa. Small little checkboxes and other targets that work well with mouse and stylus are inappropriate for fingers. Larger screens have their own problems with control sizes. Are the new controls to be used while held in the hand, laid flat upon a

Reliability

Accidental activation is common in gestural interfaces, as users happen to touch something they didn’t mean to touch. Conversely, users frequently intend to touch a control or issue a gestural command, but nothing happens because their touch or gesture was a little bit off. Traditional GUIs do have similar problems: for example, when the mouse is clicked one pixel outside the icon a user intended to activate. But at least the mouse pointer is visible on the screen so that the user can see it’s slightly off.

Since gestures are invisible, users often don’t know that they made such mistakes. Also, a basic foundation of usability is that errors are not the user’s fault; they are the system’s (or designer’s) fault for making it too easy to commit the error. When users think they did one thing but actually did something else, they lose their sense of controlling the system because they don’t understand the connection between actions and results. The user experience feels random and definitely not empowering.