How much can you trust what users tell you?

In this solo episode, we dive into one of the most slippery yet essential tools in UX research: self-reporting. From interviews to surveys, self-reports are everywhere—but they come with hidden psychological traps.

We explore:

• Why self-reported data can be both useful and misleading
• The psychological reasons people often misrepresent their own behavior
• When to trust what users say—and when to dig deeper
• The subtle difference between described and observed behavior

If you’ve ever relied on user quotes to justify a design decision—or been burned by data that didn’t translate to real-world outcomes—this episode will give you a sharper lens for interpreting what users say versus what they do.

Tune in to sharpen your research instincts and make your design decisions more psychologically grounded.

Ever wonder how certain products feel inevitable the moment they appear—rearranging entire markets overnight? In this episode of The Design Psychologist, Thomas sits down with UX pioneer Larry Marine to unpack the mechanics of truly disruptive research—the kind that yields insights so fundamental they can’t be unseen.

Most teams unknowingly skip a handful of critical research steps, blinding themselves to the knowledge that changes everything. Larry shows us how treating users, tasks, and entire processes as flows of knowledge reframes both what you look for and what you ultimately build. Along the way we probe why familiar tools like personas sometimes help—and sometimes hurt—and how principles from cognitive science give sharper edges to every question we ask.

🔍 You’ll learn

• What makes research “disruptive.” Why some methods surface game-changing insights while standard approaches miss them.
• The critical steps most teams skip. How a small shift early on can rewrite both your findings and your final design.
• Knowledge-centric mapping. Viewing users and processes through the lens of knowledge—revealing needs that action-based models overlook.
• Where personas really belong. When they clarify design decisions and when they get in the way.
• Cognitive science in practice. Concrete ways to align products with how people actually think and behave.
• A self-audit toolkit. Practical prompts to evaluate (and radically improve) your current research workflow.

Whether you’re launching a start-up or steering a mature product team, this conversation arms you with a sharper lens and actionable tools to uncover deeper, more market-shaking insights—before someone else does.

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How many participants do you need to test in order to make valid research claims? In this episode, we dive deep into the science and psychology behind sample sizes in user testing. Whether you're working with five users or five hundred, the number you choose can shape the story your research tells—and how credible your findings appear to stakeholders.

• Why sample size is one of the most misunderstood elements in product research
• The psychological impact of “too few” vs. “just enough” users in high-stakes design reviews
• Whether the popular idea that "you only need to test five users" is a myth or a useful research guideline
• How to determine the right number of participants based on your research goals

By the end of this episode, you’ll have a clearer, more confident approach to choosing sample sizes. This will help you create better, more intuitive, and scientifically sound designs.

Never miss an episode.
If you’d like a note when new episodes of The Design Psychologist drop, join the newsletter. I’ll send you fresh insights on psychology and design straight to your inbox.
[Sign up for the newsletter here—it only takes a moment. → https://3leafconsulting.substack.com/]