A Tale of Two Approaches to Innovation – IxD vs. Proto/Test

Article summary

“So you can’t go out and ask people, you know, ‘What’s the next big thing?’ There’s a great quote by Henry Ford, right? He said, ‘If I’d have asked my customers what they wanted, they would have told me ‘A faster horse.’” – Steve Jobs, 2008

This quote from Steve Jobs was very much on my mind this summer when Alan Cooper sent out a series of tweets about differences between interaction design (IxD) and the prototype/test/learn (proto/test) approach to product development.

Alan’s tweetstorm, itself thought-provoking and recommended, set off a long discussion between a number of industry colleagues about the virtues of proto/test and its differences from interaction design. It occurs to me that newcomers to this community and this discussion might miss out on some of the richness of this conversation without a bit of extra context, so in this post, I’ll attempt to offer that context.

The entire discussion is about how we frame and solve problems. What is the problem? How do we decide which problem to solve? Should we solve the problem? Why should we solve the problem? How do we solve it? How do we decide which solution is best? When do we check that we’ve solved the problem? How do we know we’ve solved the problem?

I’m not going to get into the details of how one might go about answering those questions. Instead, I’m going to highlight the key differences between proto/test and interaction design.


I’ll be making some gross generalizations about these two approaches. My goal is to highlight differences, not necessarily to give the precise, accurate description of each approach.

The proto/test approach

This method involves taking the quickest approach you can to getting a solution into the hands of users so you can test it. Prototype an idea, and then test it with users to see if it is successful or needs modification. Continue to iterate until you find a solution that effectively solves the problem.

The IxD approach

The interaction designer’s approach is to start from a semi-tabula rasa state. The IxD begins with research to understand the problem from the user’s position. Research gives the interaction designer the raw material to build an understanding of the problem and knowledge of human cognition patterns & principles. The designer can then begin to diverge and converge on what the problem is and how it might be solved.

The interaction designer also commonly conducts further user research within the problem space as doubts or questions arise. Further input from users might help the IxD decide which of many possible problems should be solved.


Is there really a difference here? Both approaches interact with the user. Both are solving problems. After all, interaction design certainly incorporates elements of prototype/test at different points.

The differences, I believe, are in how each approach treats the user. Proto/test starts with “my” idea and “my” artifact. The focus is on validating it by testing it with users.

IxD starts with the user. The focus is on serving the user. Proto/test treats the user as a binary test subject, but IxD treats the user as an important source of input and knowledge on a journey of discovery about both problems and solutions.

Proto/test can only take you down one branch of a binary decision tree. It can’t really facilitate divergence into undiscovered country or offer innovation. It will only refine an existing solution. Because IxD comes to the user for dialogue and input, IxD can make leaps all over the realm of the possible as new ideas arise.

And yet, IxD isn’t the practice of asking users what they want. IxD looks to users for input throughout a collaborative, human-centered process of discovery and definition. But IxD also looks to other disciplines like HCI, human cognition & psychology, business, art, etc. to offer additional input into the problem space.

It’s a more expansive approach that allows for a more complete definition of a problem space and its possible solutions. It leads us to “the next big thing” and incentivizes success by mainting dialogue with the user.

Going back to that initial quote, a proto/test approach probably would have delivered a very fast, effective horse. Maybe it would have greatly improved buggy design. But interaction design is the type of approach that resulted in the first mass-produced car. It’s the type of approach that brings successful innovation.