5 Why's

The 5 Whys method is an iterative interrogative technique pioneered at Toyota Motor Corporation in the 1930s to explore the cause-and-effect relationships underlying a specific problem. By working back the cause of one effect to another up to five times, designers can expose root causes and explore effective solutions.

“Be ahead of the times through endless creativity, inquisitiveness and pursuit of improvement.” — Sakichi Toyoda, Japanese industrialist and inventor who formulated the 5 Whys method

See why 5 Whys is such a valuable tool.

Dig Deep to the Root Cause with 5 Whys

To ask why something happened is a natural, effective way to uncover a problem, be it a high bounce rate on a website, a marketplace failure or anything else you may want to know about users, etc. However, cause-and-effect chains can be long and complex. Whether they occur in the natural or human world, end-result events rarely happen in isolation with only one cause to trigger them.

The effects of one action or condition can be so far-reaching that it’s easy to jump to conclusions when you look at the end result. The greater the number of removes—or steps in a cause-and-effect chain—the more effort and insight it will take to work your way back to what actually started the whole sequence of events that ultimately resulted in the problem at hand. If you overlook any factors involved, you might end up making assumptions—and it’s essential to discard assumptions in user experience (UX) design.

The 5 Whys method was developed to work back to a root cause of a mechanical problem by a total of five removes. Toyota’s famous example illustrates the simple nature but immense power of the technique:

  1. Why did the robot stop? The circuit overloaded, making a fuse blow.
  2. Why? There was insufficient lubrication on the bearings, so they locked up.
  3. Why? The oil pump on the robot wasn’t circulating enough oil.
  4. Why? The pump intake was clogged with metal shavings.
  5. Why? There was no filter on the pump.


In UX design—and particularly service design—system failures can be far more intricate than this. Users are humans who act in complex contexts, and their behaviors (and reasons for these) can be difficult to decipher, especially with so many channels and parts of their user journeys for you to examine. Most of what we first see when we look at an apparent problem (or, rather, its end result) is just on the surface.

Symptoms can be misleading. On that note—and even more importantly for modern designers—the 5 Whys is an essential tool to dig down to root causes on a bigger scale. As cognitive science and usability engineering expert Don Norman advises in his 21st century designhuman-centered design and humanity-centered design approaches, designers who want to effect real change in solving complex global-level problems need to get beneath the symptoms and apparent causes to discover and address what’s really going on. If you don’t solve the right problem—and work with the root cause—the symptoms will just come back.

You can use 5 Whys anytime in your design process, but it’s particularly helpful early on when you need to understand the problem facing your users, customers and/or stakeholders. As such, it’s a valuable aid in design thinking. When you conduct user research, the answers you can get by asking “why” repeatedly can arm your design team with many insights from users—insights which you can leverage to identify the real or underlying problem, and then iteratively gear your ideation efforts more accurately around it. You can use 5 Whys to:

  • Determine what’s important from the user’s/customer’s/stakeholder’s viewpoint.
  • Explore why users/customers/stakeholders think, feel and do what they do.
  • Analyze the information.


How to Use 5 Whys to Find the Root Cause

Five Whys is especially helpful to use in the empathize stage of design thinking, when you’re gathering the information you need so you can proceed to define the problem to address. It’s exactly as it sounds: you:

  1. Base the first question on the apparent end result.
  2. Form the second question on the answer to this.
  3. Form the third question on the answer to the second question.
  4. Form the fourth question on the answer to the third.
  5. Form the fifth question on the answer to the fourth.

For example: “Not as many customers are subscribing to the website’s newsletter after the design changed.”

  1. Why? Most of them click the subscription-related button within two seconds after it appears.
  2. Why? Because they’re used to seeing subscription-prompting pop-ups.
  3. Why? Because the internet is full of these.
  4. Why? Because organizations have grown used to deploying these with an automatic opt-in dark pattern for users to find it harder not to subscribe.
  5. Why? Because automatic opt-out buttons or allowing users to freely think about newsletter subscriptions (i.e., without guiding them with a design pattern) mean fewer subscriptions.

Here, it appears the designer failed to use the automatic opt-in design pattern.


  • You can frame your “why” questions with different wording (e.g., “What do you think made that happen?”).
  • Keep asking until you get to the root cause of why your users feel or behave a certain way. For example, if they say, “Because I felt like doing that,” try to prompt them to evaluate their statement (without annoying them).
  • You can ask fewer (or more) questions, whatever works.
  • Ask “Why?” even if you think you already know the answer: you may be surprised what insights you can evoke.

Learn More about the 5 Whys

Take our 21st Century Design course, featuring the 5 Whys template: https://www.interaction-design.org/courses/design-for-the-21st-century

Read this UX Planet piece for in-depth insights on 5 Whys: https://uxplanet.org/design-principles-root-of-the-problem-3389991c9e50

This blog neatly captures further insights regarding the 5 Whys: https://usabilla.com/blog/to-the-users-core-question-in-5-whys/