UX & research
Prototype the part that could change your mind
The most useful prototype tests an important assumption, even when that means leaving the polished parts of the product unfinished.
By Josh Child6 min read
In this perspective
When a prototype becomes easier to build, it becomes more tempting to build the whole thing. A complete navigation, attractive dashboard, and realistic settings page can make an idea feel ready for a serious discussion. They can also consume attention before the team has tested the assumption that matters most.
I want a prototype to help us make a decision. That means being clear about what could change our minds, what evidence would be useful, and which parts of the experience need to be real enough to learn from. The answer is not always the homepage or the first step in the flow.
AI-assisted development gives me more ways to explore an interaction. The discipline is choosing an experiment that deserves that speed.
A lesson from a complex experience
The Genographic project connected scientific information with an interactive ancestry experience. I led the experience work and coordinated delivery with scientists, stakeholders, designers, and engineers. The team had to present complex data in a way a general audience could explore without distorting its meaning.
Looking back, one lesson I documented was that I would prototype interactions earlier. We spent longer in design cycles than was necessary before testing some assumptions. A more focused functional prototype could have helped us discover what did not work before investing further in detailed design.
That reflection is specific to the work, but the principle is broadly useful. The part that is hardest to represent in a static composition may also be the part that determines whether the product is understandable. Waiting until the surrounding screens are polished can delay the most valuable learning.
Name the uncertainty before choosing the format
A prototype is a means of investigation. A sketch, a clickable sequence, and a functional slice can all be useful, depending on the question. Choosing a high-fidelity format before identifying the uncertainty can lead to a lot of work that answers very little.
Imagine a scheduling concept. The main uncertainty might be whether staff understand the proposed availability rules. A simple interface with realistic examples could expose that issue. If the uncertainty is whether the system can fit a complex combination of constraints, a clickable mockup cannot establish feasibility. The team needs a different kind of experiment with engineering involvement.
I would write a short statement before building: we need to understand whether this person can make this decision using this information. That sentence keeps the prototype tied to a task. It also helps participants and stakeholders understand what feedback will be useful.
Build enough context for a fair test
Focused does not mean context-free. A single screen may be the right scope, but the participant still needs to understand why they arrived there and what they are trying to accomplish. Otherwise, the test measures their ability to interpret an isolated artifact.
I would provide a realistic starting state and a clear task without explaining the interface. If a product depends on information from an earlier step, that information should be present. If the next action changes a record, the prototype should show enough of that result to reveal whether the person understands the transition.
The goal is to remove irrelevant work while preserving the conditions that make the question meaningful. A prototype can use sample data, but the data should contain the complexity being tested. Perfectly tidy records may hide the reason the real task is difficult.
Use AI to shorten the distance to a question
AI-assisted development can help turn a design idea into something interactive. I have used it in projects such as the Dugout beta and Hoopes Vision Atlas demo. Those examples reflect a combination of my product and design work with AI assistance during implementation.
For a new experiment, I would use that assistance to create the smallest useful interaction, then inspect its behavior. Generated functionality still needs to match the intended test. If the prototype silently accepts impossible inputs or fills missing information with plausible values, it may create misleading confidence.
I would also separate simulated behavior from functioning behavior during reviews. A button that displays a prepared sample response can test presentation. It cannot establish that a live system will produce that response reliably. The review should be clear about which conclusion the prototype can support.
Give the prototype a decision boundary
A prototype review can become a collection of preferences unless the team knows what it needs to decide. I would define the decision before presenting the artifact. Are we choosing between two workflows? Deciding whether a concept is understandable? Identifying a technical dependency that could block delivery?
The evidence does not have to produce a simple yes or no. It may reveal that the idea is promising for one type of user but requires a different path for another. That is useful if it affects scope, sequencing, or the next research question.
GOV.UK's guidance on alpha work describes focusing prototypes on risky assumptions rather than making every part production-ready. I find that distinction helpful when deciding what to leave unfinished. The unfinished parts are a deliberate boundary around the learning objective.
Pay attention to hesitation and repair
An effective prototype test gives people room to misunderstand, recover, and explain their reasoning. If I guide someone through each step, I may learn that the interface works with a helpful designer beside it. That is a different claim from the product being usable on its own.
I would look for moments where the person pauses, changes direction, or invents an explanation for what happened. A successful click can conceal a mistaken assumption. Someone may reach the final screen while believing a draft has already been sent or a recommendation has been approved.
Those observations should connect back to the original question. Some issues are important but outside the current experiment. Recording them without immediately expanding the prototype helps keep the work focused. The next iteration can address the findings that most affect the decision.
Retire the experiment when it has done its job
A prototype can become difficult to discard once it looks convincing. Stakeholders see working screens, contributors see invested effort, and the path of least resistance is to keep adding features. That can turn experimental shortcuts into an accidental foundation.
I would make the transition explicit. What did we learn? Which assumptions remain? What would production delivery require that the prototype does not provide? Engineers should be involved in answering that last question. A usable experiment does not automatically establish maintainability, security, or operational readiness.
Some prototype work may carry forward. Some should be replaced. The decision should follow the product's needs rather than the emotional weight of a polished artifact.
Keep the question more important than the artifact
The best reason to prototype faster is to learn sooner. A focused experiment can help a team stop an unhelpful direction, refine a promising one, or expose a dependency before it shapes the entire plan.
I want the result of a prototype review to be a clearer decision, not just a more complete set of screens. When the question stays visible, the format can remain practical and the work can remain honest about what it proves. That is how faster tools can improve discovery instead of simply accelerating our first assumptions.