Design fundamentals: constraints

Default avatar.
February 05, 2013
Design fundamentals: constraints.

ThumbnailThe concept of constraints in design can be defined as the practice of limiting user actions on a system.

Constraints limit the actions that can be performed by the user, thus increasing the usability of the design and reducing the likelihood of operator error.

There are two models of constraint: physical and psychological. Physical constraints decrease the sensitivity of controls and prevent or slow undesired actions and psychological constraints will aid in the intelligibility of your design and make it more intuitive.

Let’s take a closer look at the finer points.

Physical constraints

The first model, physical constraint, refers to the ability to constrain the user’s actions using a physical object, be it actual or virtual. There are three types of physical constraints: paths, axes, & barriers.

Paths restrict user action to linear or curvilinear motion. This is accomplished most frequently by the use of grooves or channels. Paths are particularly useful in controls where the control variable range is relatively small. A familiar example would be the volume bar on the iTunes interface. As you can see, there is no way to misuse this module.

Axes direct user action into rotary motion. This has several benefits, most notably enabling the control to be of expansive or infinite in length, yet able to exist in a small space. An example of this is the rotate tool within the reflect dialogue box in Illustrator CS6. Here you are given the option to rotate the object 360 degrees with an axis-based control guiding your movement.

Barriers absorb or redirect user actions. By doing this, barriers are able to slow, deflect, or cease user actions that are not conducive to a successful experience. A sound example of creating a barrier is the common “are you sure you want to perform this action?” dialogue box that can be found on many interfaces, particularly e-commerce interfaces.

Psychological constraints

The second model, psychological constraint, refers to the technique of limiting possible user actions by leveraging the way people perceive their environment. There are three methods of executing psychological restraints: symbols, conventions, and mapping.

Symbols communicate through text, icons, and sounds. Symbols are useful for categorizing, clarifying, and cautioning users about certain actions. A good example of symbols being used for constraint in design would be the error sound that a PC makes when an entry is incomplete or invalid. This serves as a warning to the user that additional actions are necessary.

Conventions constrain user action by calling upon learned customs and exercises. For example, picture a red button next to a green one. One need not think very hard to understand the implication of using one vs. the other.

Mappings influence user behavior by creating a perceived relationship between elements of a particular design. For example, a set of radio buttons placed closely to a list of choices implies the relationship between the two elements. Mappings are useful for illustrating possible actions for the user based on prominence, position, and appearance of the controls.

Using constraints

Whilst constraining user behaviour instead of enabling it may initially seem counter-intuitive, by limiting what actions users can undertake, we can focus on perfecting those limited options. Understanding and implementing constraints will aid in usability and help your users engage your design with minimal error, thus creating a more effective overall experience.

What forms of constraint are most effective? How carefully do you plan constraints in your UI design? Let us know in the comments.

Featured image/thumbnail, contraint image via Shutterstock.

Mike Redaelli

Mike designs high-grade graphics for entrepreneurs & developers. He is also a freelance writer, which should be rather obvious at this point. Connect with him at www.mikeredaelli.com.

Read Next

10+ Best Resources & Tools for Web Designers (2024 update)

Is searching for the best web design tools to suit your needs akin to having a recurring bad dream? Does each…

3 Essential Design Trends, April 2024

Ready to jump into some amazing new design ideas for Spring? Our roundup has everything from UX to color trends…

How to Plan Your First Successful Website

Planning a new website can be exciting and — if you’re anything like me — a little daunting. Whether you’re an…

15 Best New Fonts, March 2024

Welcome to March’s edition of our roundup of the best new fonts for designers. This month’s compilation includes…

LimeWire Developer APIs Herald a New Era of AI Integration

Generative AI is a fascinating technology. Far from the design killer some people feared, it is an empowering and…

20 Best New Websites, March 2024

Welcome to our pick of sites for March. This month’s collection tends towards the simple and clean, which goes to show…

Exciting New Tools for Designers, March 2024

The fast-paced world of design never stops turning, and staying ahead of the curve is essential for creatives. As…

Web Tech Trends to Watch in 2024 and Beyond

It hardly seems possible given the radical transformations we’ve seen over the last few decades, but the web design…

6 Best AI Productivity Apps in 2024

There’s no escaping it: if you want to be successful, you need to be productive. The more you work, the more you…

3 Essential Design Trends, February 2024

From atypical typefaces to neutral colors to unusual user patterns, there are plenty of new website design trends to…

Surviving the Leap from College to Real-World Design

So, you’ve finished college and are ready to showcase your design skills to the world. This is a pivotal moment that…

20 Mind-Bending Illusions That Will Make You Question Reality

Mind-bending videos. Divisive Images. Eye-straining visuals. This list of optical illusions has it all. Join us as we…