Picking the Right Degree of Control for User Interfaces

 

Microsoft User Experience Group
October 2003

Contents

User Control vs. Leading the User
Control in a User Interface
Regular Activities and Infrequent Tasks
Usage Profiles
How Much Control Should You Give?
Different Techniques for Different Degrees of Control
Getting Control Right
Other Factors that Affect Control

Your application's user interface is an intermediary, situated between the user and the computer. To some extent, the user and the software rely on each other. A user cannot directly manipulate bits of data in memory or storage hardware, nor can the software's limited capacity for intelligence allow it to independently determine the desired result for any non-trivial task. In a way, the user and the software collaborate. This collaboration requires you to make a critical decision: which of the two will control the interaction—the user or the software?

The decisions you make about how your software and your users collaborate will significantly affect the user experience of your application—and ultimately the success of your application as a whole.

User Control vs. Leading the User

Giving the user control is like putting someone in the driver's seat of a car. You might think that the person always likes to drive. While there are times when driving is fine (if, for example, they know the route well, they like to drive, or they feel rested), there are other times when having someone else drive is better (if, for example, they're in an unfamiliar area, they don't like to drive, or the route is boring). Regardless of whether the person is a driver or a passenger, they can still reach their destination; but the situation determines which role is ideal.

In the same way, your users can either be in control of the interaction, or they can be lead through the interaction by the software. There is an established set of UI elements and techniques suitable for an interface in which the user is firmly in control, and there is an equally valuable set of elements and techniques suitable for an interface that controls the interaction and leads the user through a task.

Control in a User Interface

What does it mean for software to put the user in control? It means that the software assumes users know what they want to accomplish. Most of the time the software is waiting for the user to give commands or enter data. The software presents the user with a range of commands. The user selects a command, the software executes it immediately, and then the software resumes waiting for commands. The software doesn't second-guess the user's methods, distract the user, or offer instruction beyond that which is explicitly requested.

What does it mean for software to control an interaction with the user? It means that the software assumes it knows the best way for the user to accomplish the task, and will lead the user. The software begins with a rough picture of the user's situation and intended result, and may ask the user for details that are sufficient enough to complete the picture. These questions have a narrow scope, and constrain the user's responses to meaningful answers. The software may offer to educate the user on the general process and on the repercussions of certain answers. In particular, the software may take pains to confirm the user's intentions before performing irrevocable or destructive actions.

Either approach allows the user to accomplish the task, but the situation determines which approach is best. You might think it's best to always give the user control, because users surely know what they want and can produce a better result than the software. But users may not actually know what they want, the task may be long and boring, and the perfection of the result may not be the user's main concern. The user may be more concerned with the amount of time and energy needed to complete the task. Having the software lead the user might produce a result that is good enough for the user's purposes, at a lower cost than if the user were in control.

Control is not an all-or-nothing proposition—it's a question of degree. You can make independent determinations about control at different levels of your application. For example, your application might put the user in control overall, while at times reasserting control and leading the user; or, it can generally lead the user, but will offer user control for certain operations.

Regular Activities and Infrequent Tasks

Determining when the user should have control should not be based on distinguishing between expert and novice users, or on the user's intelligence or familiarity with computers. For example, a brilliant industrial engineer who is skilled in a complex modeling application may not want to learn a complex interface for sending the occasional fax.

Control is based on an essentially economic point: to understand and learn a user interface, people must invest valuable time and energy. In exchange for this investment, people demand an appropriate return in either the short term (accomplishing a task at hand) or the long term (learning how to accomplish the same task or similar tasks more quickly in the future). To understand the economics of learning interfaces, it's useful to understand how people use a computer to perform tasks.

Software applications and features are tools—people use them to perform tasks, not to learn interfaces. (Computer games are the exceptions to this rule. In games and other forms of immersive entertainment, mastering a complex UI may be part of the appeal.) A task is anything a user does to accomplish a result, such as writing a report, balancing a budget, sending e-mail to a friend, and so on. Each person may perform many tasks over time, but he or she has a small set of tasks that need to be done all the time. These frequently performed tasks are done in the context of the regular activities users do repeatedly. For example, a financial planner may regularly meet with clients, review financial statements, investigate investment opportunities, prepare recommendations, and record billable time. This same person may also regularly communicate with friends, read news, and listen to music.

Users are typically willing to invest time and energy to learn how to perform the tasks that are necessary for their regular activities. Since they perform these tasks frequently, the initial investments of time and energy produce useful long-term returns. They perform tasks more efficiently over time, which in the long-term saves time, and more importantly helps users advance their careers and achieve other life goals. Once a user has found a way to complete a task, it's rare that the user will reinvest the same amount of time and energy to learn a new way to accomplish the same task.

Infrequent tasks are not part of a user's regular activities. Investments in infrequent tasks must pay for themselves in the short term. For example, most computer owners don't set up computers for a living, so they hope to be able to set up a new computer with a minimum investment of time and energy. They have no interest in learning to perform this task more efficiently or effectively in the long term, because that knowledge will likely become forgotten or obsolete by the time they perform the task again.

You must decide if your target users will use the software for a regular activity or an infrequent task. You must make this decision for the application overall, and often for individual features within the application as well.

Usage Profiles

Because most software has a wide variety of users, you need to develop a feeling for your product's usage profile: the rough proportion of people who use the product for regular activities versus those who use it for infrequent tasks.

It's easiest to design software that focuses on a single category of users in your product's usage profile. You can create flexible interfaces that can handle a spectrum of users, but the wider this range is, the harder the design task becomes. Moreover, work aimed at one user segment is bound to affect others. It's not easy to offer guidance to the infrequent user and also stay out of the way of the regular user. It's similarly difficult to offer regular users a tool that won't get noticed by—and confuse—the infrequent user.

It's particularly challenging (and sometimes impossible) to design a product whose usage profile has users bunched at either end of the spectrum. For instance, the average user may set up a new computer once every few years, but an IT professional may set up computers many times a day. If you try to create a single interface that addresses the needs of such disparate groups, you may end up satisfying neither. The solution may be to create different products or features for each type of user.

You must also watch for fringe cases—the person who uses some obscure feature twenty times a day, or the person who uses a complex application once a year and expects to produce great results. It can be hard to willingly turn away a potential customer, but attempts to include fringe cases in your target users can compromise the interface's design, to the detriment of the majority of your users.

Every product has one category of users who are so far beyond the fringe that they don't belong in the usage profile at all. These users are the product's creators. If the developers of a software product have to click hundreds of times through a screen that their actual users will see only once, they may be tempted to apply design techniques appropriate for regular activities to what are in fact infrequent tasks. You must recognize this temptation and hold your ground against it.

How Much Control Should You Give?

Once you determine if a task will be performed infrequently or as part of a regular activity, you can determine the degree of control the user needs to have to perform that task. You should base this decision on your product's usage profile.

As mentioned above, the user must invest time and energy learning a user interface in order to control it and direct the action. Because users are more willing to invest for the long term in tasks they perform as part of their regular activities, it follows that giving the user control generally makes sense only for regular activities. People who do something day in and day out are more willing to do what it takes to get good at it. Having done so, they will want to be in charge.

In contrast, because people are only willing to make small investments in infrequent tasks, software should guide the user through those tasks. Guiding the user should never be viewed as condescending. People often need to perform tasks they don't know how to perform (or don't care to know how to), and a computer can be powerful enough to help them succeed at those tasks.

For a real-world parallel, suppose you needed to give a first-time visitor driving directions to your home or office. You would probably try to maximize the visitor's chance of success by describing the simplest route, even if it wasn't the fastest way. The visitor wouldn't find the simplified directions condescending, but would probably welcome the thoughtful help. The visitor might never travel this route again, and therefore would hardly be interested in learning or memorizing the best possible way. The visitor would be entirely concerned with reaching the destination with minimum stress.

As observed earlier, control is a matter of degree and not absolutes. Users can never be completely in control—they can't hold bits of data in their hands—so they always act through an intermediary interface that removes some degree of control. At the other extreme, even if the software provides extensive guidance, it must still confer a minimum degree of user control. The computer should always be responsive (for example, to mouse movements), and the user must be able to stop or switch away from the task to do something else.

Different Techniques for Different Degrees of Control

Tasks that are part of regular activities require a different UI design technique than infrequent tasks. Once you decide how much control is appropriate, that decision will pervade your product's design.

If the user is in control, you need to create software that functions as an extension of the user, and could be described as an instrument. Like scientific or musical instruments, software instruments can do precise work, but they require time to master and can be delicate or dangerous things. With a small slip, an inexperienced user could alter work or damage their system. Since instruments require user control, they are appropriate for performing tasks as part of regular activities. Examples of software instruments include most document editing applications such as Microsoft® Word and Microsoft Excel, as well as electronic e-mail programs such as Microsoft Outlook®.

If the software leads the user, you need to create a sufficiently detailed application design so that the software can make good decisions for the user. Depending on the situation, the software might play a role such as advisor, guide, or specialist—for example, a network setup wizard advises the user about what hardware to buy, and then guides the user through the process of setting up the network.

It's worth restating that leading users through a task doesn't mean the result will be inferior. If the software is well designed, users may achieve better results by being guided by the software than if they had been left in complete control.

Getting Control Right

To correctly calculate who should be in control of the interaction, it may help to visualize the relationship between the regularity of a task and control of the interface, as shown in Figure 1.

Figure 1 Task regularity and interface control

Generally, only the lower-left and upper-right quadrants are desirable for software designs; the other two quadrants usually lead to user frustration.

When you revise an application to improve various features, the improvements often directly address earlier miscalculations about control. You may realize that a given feature in your product isn't used as often as you'd imagined, and respond with a new interface to lead users through that task. Alternatively, you may realize that one user segment performs a certain task much more often than you had expected, and offer new tools that give this segment control of that task.

Other Factors that Affect Control

The rule of thumb is to put the user in control of tasks performed as part of regular activities and guide them through everything else. However, other factors can influence this decision.

For example, you should consider fundamental differences in the sorts of tasks that humans and computers each do well. Certain tasks cannot be performed by computers—for example, creative tasks like writing a speech. Even if a user needs to write a witty and engaging speech only occasionally, the computer can't do it for them.

On the other hand, computers do a better job with repetitive and error-prone tasks (for example, copying a thousand numbers), intricate tasks (for example, applying a complex shading effect to a photograph), or long, time-consuming tasks (for example, watching a particular network location day and night for signs of change). Even if users could produce a marginally better result, they will typically prefer that the computer take control of such operations.

If learning an interface is an investment that demands an appropriate return, it's worth considering ways to lower the investment cost or raise the return. For example, consistency in user interfaces can lower the cost of learning a new product. If users are already familiar with a product that they use to perform a regular activity, they may be able to use a very similar product to perform an infrequent task, even if they haven't used the other product before. Additionally, if the quality of an application's output is extremely high, the return may justify learning the application, even for an infrequent task.

Sometimes an interface that leads the user through a task isn't practical. Designing such an interface requires developing a task model that is sufficiently detailed and accurate—and that can be implemented in code. Depending on the task, creating and implementing a task model can be prohibitively expensive. It may be cheaper to design and implement an interface in which the user is left in control, because giving the user some way to perform this task is better than no way at all.

Finally, users with different abilities and personalities are more or less open to user interfaces that require control. The drive for control can motivate some people to learn to control an unfamiliar interface. Some people learn or remember things very easily, lowering the investment required to achieve control. Some people take a long-term view of investments in performing tasks, and readily invest in learning an interface if they estimate they will perform a task more than once. It's worth remembering that software professionals possess all these characteristics, and therefore that your understanding of the interface lies far beyond the fringe of users that matter in the design of many products.

©2003 Microsoft Corporation. All rights reserved.

The Microsoft Windows Code Name "Longhorn" User Experience Guidelines are produced by the MSX (Microsoft User Experience) group.

Show: