How To Improve Design Usability: Minimizing Errors Part II

When designing websites and other applications are there ways we can guide users to make correct choices, help them interact with our systems, and generally make our systems more usable? A variety of strategies exist to improve our interface designs and today we’ll talk about 2 of them.

Flickr xml error

Last week we looked at errors in general. We looked at the different types or errors one could make and what might cause them. We also looked at general strategies to help prevent and minimize the effects of errors and talked in more detail about one of those strategies, affordance. This week we’ll look at two more strategies in detail, mapping and nudging.

First a quick reminder of all the strategies we’ve covered and will be covering in this series of posts.

  • Affordance is the idea that the physical characteristics of a design influence its function.
  • Mapping is the relationship between design controls, their movements, and their effects on the design element(s) they control.
  • Nudge is a method for predictably altering behavior through design context without restricting options or significantly changing incentives.
  • Constraints are methods for limiting the actions that can be performed on a system.
  • Confirmations are techniques for preventing unintended actions by requiring verification of the actions before they are performed.
  • Forgiveness is the idea that designs should help people avoid errors where possible and minimize the consequences of errors when they do occur

If you remember affordance was about designing things in a way that makes instructions as unnecessary as possible. Ideally the design of an element alone is enough to understand how to use it. Mapping is a similar strategy to affordance in that good mapping makes it easy to use the controls of a system without instructions.

Let’s dive in to discussing mapping and see how it works.

map of the world


Mapping is the relationship between design controls, their movements, and their effects. Good mapping between controls and their effects leads to greater ease of use. When the effect of the control corresponds to expectations about the function of the object being controlled, mapping is good .

Steering wheel fron an old Ford

Turning the steering wheel to the left makes the car turn left. It’s what you would expect without knowing in advance how turning the steering wheel would actually affect the car. Imagine for a moment if turning the steering wheel left turned the car tight?

Car window controls

Consider the switch controls that raise and lower a car window shown above. When placed on the door moving the switch up raises the window and moving it down lowers the window.

When placed on the armrest which direction raises the window? Forward or backward? In the image above can you easily tell which way to press the buttons to move the window up or down? With the switch on the armrest the mapping isn’t as strong.

Good mapping is primarily a result of similarity in one of three things.

  • similarity of layout – window controls are an example of mapping through layout
  • similarity of behavior the turning of a steering wheel is an example of mapping through behavior
  • similarity of meaning an emergency shutoff switch colored red is an example of mapping through meaning (red generally means stop)

Segway and rider made from Lego

Another example of good mapping is the Segway. Lean forward and move forward. Lean backward and move backward. No instructions necessary.

An example where mapping isn’t always as good as it could be is the burner controls on a stovetop. Burners are often placed in a two by two grid while controls are often placed in a single row. Does the left most knob control the left front or left read burner?

The image below shows a stovetop with good mapping between controls and functions. A quick look makes it easy to determine which knob controls which burner.

Stovetop burners and controls with good mapping

Simple control-effect relationships are best when it comes to mapping (PDF) and controls should ideally be placed so their layout and behavior corresponds to the layout and behavior of the object being controlled.

It’s best to avoid using a single control for multiple functions if possible. It’s difficult to achieve good mapping with a one to many relationship. However when it can’t be avoided try using distinct modes to indicate which is the active function. Perhaps different colors for different active functions.

Also be careful with conventions due to cultural differences. In the U.S. moving a light switch up turns it on and moving it down turns it off. In england the opposite is true.

When mapping is done well controls and interfaces are intuitive (PDF) to use.

Dirt path through the woods


Nudging is a method for altering behavior in a predictable way without restricting options and without significantly changing incentives. You allow the user to do what they want, though you subtly guide them to taking certain actions or choosing certain options.

People generally prefer the path of least resistance. When the path of least resistance leads to their desired outcome people are happy. When the path of least resistance leads to undesired outcomes people aren’t so happy.

An example of nudging is enrollment in an employee pension plan. When employees are signed into the plan automatically they’re more likely to contribute. When employees first need to sign up for the plan they’re less likely to sign up and contribute.

Most employees would likely want to be part of the plan and contribute since it’s for their own benefit. A nudge that signs them up by default, while still allowing them to opt out, makes this more likely to occur.

There are several common ways to nudge.

  1. Defaults – Select the defaults that do the most good and the least harm
  2. Feedback – Provide visible and immediate feedback for actions and inactions
  3. Incentives – Avoid conflicts in incentives and align incentives with desired actions and preferred behaviors
  4. Structured choices – Simplify and filter complexity to make decision making easier
  5. Visible controls – Show clear performance measures so users can immediately assess their performance against a goal or goals

Achievment award

When behavior modification is important nudging can be an effective way to achieve that modification. With defaults make sure to set them to correspond to the most desired outcome and not the most conservative outcome. The default is the path of least resistance and most people will leave them. Feedback should be clear, visible, and immediate and should reinforce the desired action, while mildly punishing the undesired action.

Offer more incentives for performing the desired action, while being careful to avoid conflicts in incentives. Offer clear choices in a simple structure, especially where decision making is complex. Offer clearly visible goals and performance status.

While it’s hard to read below (click here to see it full sized), the image is a series of notes for using tv to give incentives to people to recycle.

Handwritten notes for using media to give incentives for recycling trash

Nudging can be a useful way to subtly alter behavior toward desired choices by aligning the path of least resistance with the most desired outcomes.

Additional Resources

Segway and rider built with Lego.jpg


As I mentioned last week we’d prefer people not make errors when interacting with our designs. It’s going to happen though no matter how hard we try to prevent it. We can’t counter all errors, but we can help prevent many by guiding users toward correct actions.

Two ways we can help reduce errors are mapping controls to their effects as well as possible and nudging people toward desired actions.

Through similarity of layout, behavior, and meaning between control and effect we create good mapping and with well mapped controls we make it more obvious how someone should use our design. Much like affordance,when mapping is well conceived it’s hard to see how those controls could be used in any way other than the correct way. No instructions should be necessary.

Nudging on the other hand is a way to guide users toward better results. By setting defaults to desired outcomes, offering feedback and incentives, providing structured choices, and making necessary controls visible, we help people take the actions they most likely want to take. We lead them down a path of least resistance that is aligned with their goals.

So far in these posts we’ve been talking about strategies that help people make correct choices and take better actions. We’ve been leading people toward desired options at results. Next week we’ll take a look at strategies that prevent errors through making it more difficult for them to occur.

We’ll consider the ideas of using constraints to limit incorrect actions and confirmations to help people avoid mistakes. We’ll also look at the strategy of building forgiveness into a system to help minimize the damage from the inevitable errors that will occur.

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