Introduction

Touchscreens - Interaction of the Future? | Limitations of Touchscreens | The Ultimate Judge is the User

The Interaction Design Guide for Touchscreen Applications presents guidelines for designing the user interface for touchscreens. Typically touchscreens are operated at POS stations (point-of-sale), in museums, as city guides, or as kiosks (stand-alone advertising booths with user interaction). Users are often untrained, and interaction has to be simple and fast. These situations require a screen and interaction design, which differs considerably from normal user interface design.

Finger-operated touchscreen

Figure 1: Finger-operated touchscreen (from ELO Touch Systems)

Touchscreens - Interaction of the Future?

Touchscreens are operated with a finger or stylus. Therefore, they provide a very direct interaction - the most direct interaction that is possible on computers today. Touchscreens may be operated very fast for certain operations and require little or no training, if applications are designed adequately.

For these reasons touchscreens have many uses, especially for untrained users. Many people believe that touchscreens will replace keyboard and mouse in the future.

Limitations of Touchscreens

However, touchscreens have limitations that - to our opinion - prevent them from becoming the "universal" solution for user interface problems.

Size

Fingers have a certain size. So, screen elements have to have a minimum size, to ensure that a touchscreen can be operated with few errors. Even with a stylus, which makes possible to use smaller screen elements, there are limiting factors.

Sequential Input

Input on a touchscreen is inherently sequential: One finger is used for clicking. This slows input down compared to keyboard input where several fingers can be used virtually in parallel.

Strain

Keying in many numbers or letters by pointing with the finger is also very straining and tiring. Therefore, touchscreens make no sense in workplaces, where much text or number input is required.

Feedback

On touchscreens, there is no analogue to mouse-move events. Mouse users can move the mouse pointer over screen elements, get feedback about the selected element (e.g. by highlighting), and may confirm the selection by clicking the mouse button. Touchscreen users directly point on a screen element. If they are lucky, they can withdraw their finger if they touched the wrong screen element. On other touchscreens, the touch immediately initiates an action - there is no opportunity to cancel the action.

Drag Operations

Dragging is generally not well suited to finger-operated touchscreens; here pointing is the preferred interaction. However, this is different for stylus-operated touchscreens. Here gestures and handwriting offer promising possibilities for making interaction with computers easier and more intuitive. But here, too is the limitation of strictly sequential input.

There are also no means to constrain drag operations to, e.g. straight lines, like with mouse-based interfaces.

The Ultimate Judge is the User!

These preliminary design guidelines for touchscreens take the characteristics of touchscreens, their advantages and disadvantages, into account. Of course, these guidelines will be refined, as our experience with touchscreens grows. The ultimate judge, however, is the user. As ELO Touch Systems quote in their guidelines:

Testing a touchscreen application on focus groups will disclose the areas that need improvement.
If anyone pauses in confusion for even a moment, think how to improve the application.

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