Test Assumptions, Not Ideas.


Q: How do I get started with testing & experiments?

Dear Reader,

I've been talking a lot about experiments, lately, and maybe you'd like to dip your toe in the water?

There's a very important first step you should take that may not be obvious if you're new to experiments.

It's especially important to designers that fall in love with their solutions.

Test assumptions, not ideas.

Hidden beneath every idea are giant assumptions about how something will go. It turns out humans are terrible at predicting the future so we fill in the gaps with assumptions.

Testing assumptions helps us avoid confirmation bias and forces us to think critically about the details of an idea that we might skip if we're excited about an idea.

Product ideas that make sense on paper can fail if they don't understand the realities of messy humans in a chaotic world.

In design school, we are taught to follow the brief without question, but briefs are full of assumptions.

Questioning the assumptions within ideas can sometimes feel like a “buzzkill” when the team is on a creative high, but every idea is an assumption until it’s in the hands of a customer.

Because assumptions are beliefs, they’re not always easy to identify. Assumption Hunting™️ is how you find hidden beliefs within product ideas, and it’s best done with other people.

Upcoming Live Courses


ONLINE WORKSHOP: Leading Effective Discussions
Learn how to confidently guide discussions, even without authority.
Date: Sept. 9, 2025
Time: 6:00 PM 8:30 PM CEST
Buy a Seat


COURSE: Facilitating Workshops
Learn to design and lead engaging workshops that lead to real results.
Next Cohort: Sept 29 – Nov 6, 2025
Early Bird Ends: Aug 22 – Save €200
But a Seat


COURSE: Defining UX Strategy
Learn to design a winning strategy that aligns design with business
Basic seats available now
Buy a seat


Methods like Assumption Mapping can help you identify the risks with your team.

When you're working in highly uncertain environments like on innovation teams, opinions mean nothing.

Only the evidence behind the ideas matters, and that evidence should come from the customer or research, not the HiPPO (highest paid person’s opinion).

Assumptions are everywhere, but that doesn't mean finding them will be easy.

Sometimes, you have to simulate the idea to reveal the assumption.

Paper prototypes, storyboarding, and journey mapping can also help you recognize gaps and areas where your team is making assumptions...

Read the full article on the blog→

Until next week, start hunting down those assumptions!

Jeff Humble
Designer & Co-Founder
The Fountain Institute

P.S. If you want to dive deeper into assumption testing, check out this FREE 60-minute video on how to design product experiments from last Saturday's webinar:

Watch the Video→

The Fountain Institute

The Fountain Institute is an independent online school that teaches advanced UX & product skills.

Read more from The Fountain Institute

A Workshop Agenda No One Wants By Hannah Baker Dear Reader, Last week, I posted a fake workshop agenda on LinkedIn. The kind we’ve all been in that drains your will to collaborate. I shared it as a joke. It reached 100,000+ people • 800+ likes • 100+ comments • 20+ reposts But the comments weren’t just laughs. They were…grief. People didn’t just say “ha ha, I’ve seen this.” They said: “Oh no. I’ve run this.” The real takeaway? We’re not bad at facilitation, we have to break the status quo. We...

5 Signals That Hint at the Future of AI Interactions by Jeff Humble Dear Reader, The AI landscape is changing fast, and the way we interact with AI is changing even faster. Who knows what the UX of AI will be in 2035? Right now, most of us talk to AI through clunky, chat-based interfaces. But new hardware hints at something more human and ambient. Today, I want to share 5 signals: surprising examples from today that suggest where the future might end up, and a method used by future foresight...

When Your Strategy Slides Hit Silence By Hannah Baker Dear Reader, I’ve shared strategy before, and watched it stall. Not because it was wrong. But because the room didn’t know what to do with it. I wasn’t looking for feedback. I wasn’t asking for approval. I was hoping they’d pick it up and run with it. Instead? Confusion. Silence. They didn’t see what I saw. Not because they didn’t care. But because I’d built the strategy, not the on-ramp they needed to step into it. It’s something I’ve...