100 Things Every Designer Needs to Know About People
by Susan Weinschenk
“This book is a must-read for anyone involved in designing interactive experiences. Susan Weinschenk has distilled decades of research into a book that is both engaging and actionable. You’ll find yourself referring back to it time and time again.”
The User's Manual for the Human Brain: What Every Creator Needs to Know
Have you ever landed on a beautifully designed website only to find it completely impossible to navigate? Or downloaded a sleek, modern app that left you utterly confused about what to do next? We often assume that good design is a matter of aesthetic taste—the right fonts, a great color palette, and stylish graphics. But what if the secret to truly effective design has less to do with art and more to do with science?
This is the core message of Susan Weinschenk’s indispensable book, 100 Things Every Designer Needs to Know About People. Weinschenk, a Ph.D. in psychology, provides a fascinating "user's manual" for the human brain, revealing the science behind how we see, read, think, and make decisions. The book is a bridge between the world of psychology and the world of design, arguing that the most successful products aren't just visually appealing; they are built with a deep understanding of the user's innate mental wiring.
What You'll Learn
Why people don't actually read websites, they "satisfice" (and how you must design for it).
The surprising (and small) limits of human memory and how to avoid overloading your users.
The powerful psychological triggers like social proof and scarcity that motivate people to act.
How to use simple visual cues to guide a user's attention exactly where you want it.
Why storytelling is one of the most effective tools for persuasion and memory.
How People See: Your Design is Not Their Reality
One of the first humbling lessons from the book is that what you design is not what your users see. Their perception is heavily influenced by experience, expectations, and hardwired cognitive shortcuts.
A powerful example is the use of faces. Our brains are hardwired from birth to notice and engage with human faces. But more than that, we automatically look where the person in the picture is looking. A baby-products company, for instance, A/B tested their homepage. One version had a picture of a cute baby looking directly at the camera. The other had the same baby looking to the right, at the headline of the product copy. The result? The version where the baby was looking at the headline had dramatically higher engagement with the text. The baby’s gaze acted as an unconscious directional cue, telling the user’s brain exactly where to look.
How People Read: The Myth of the Attentive User
Here’s a hard truth: people don’t read your website. Not really. We like to imagine our users carefully reading every word we’ve crafted, but the research shows something very different. People don’t look for the best option; they look for the first reasonable option. This is a concept called "satisficing."
Users scan pages in a pattern that researchers have identified as roughly F-shaped. They scan the top headline, then scan down the left side of the page looking for keywords, and might read across the middle if they find something interesting. This means long, dense paragraphs of text are essentially invisible.
To design for this reality, you must embrace scannability:
Use clear, informative headlines.
Break text into short paragraphs.
Utilize bulleted and numbered lists.
Bold key terms and phrases.
This isn't "dumbing down" your content; it's formatting it to align with how the human brain actually processes information online.
How People Think: Respect the Cognitive Load
Our brains are powerful, but our short-term, working memory is incredibly limited. For decades, designers cited a "magic number" of seven items that people could hold in their memory. But Weinschenk points to newer research showing the number is actually much smaller—more like three or four.
Every piece of information you ask a user to remember—a coupon code, a navigation item, a step in a process—adds to their "cognitive load." When this load becomes too heavy, users get frustrated, make errors, and abandon the task.
The solution is a design principle called "progressive disclosure." Don’t show everything at once. Show only the necessary information for the current step and provide a clear link for more advanced options if the user wants them. A clean settings screen with a simple "Advanced Settings" link is a perfect example. It respects the cognitive load of the average user while still providing power to the expert.
How People Are Motivated: The Unseen Triggers
Why do people decide to act? Often, it's due to powerful psychological triggers that we are not even consciously aware of. Weinschenk highlights several that are crucial for anyone designing an experience.
Social Proof: We are social creatures who look to others for cues on how to behave, especially in uncertain situations. This is why testimonials, user reviews, and follower counts ("Join 50,000 other happy customers!") are so persuasive. They signal to our brain that this is a safe and trusted choice.
Scarcity: We are wired to want things that are limited or that we might lose. "Only 3 seats left at this price!" or "Offer ends Friday" are not just marketing gimmicks; they are powerful psychological motivators that tap into our innate fear of missing out (FOMO).
Variable Rewards: The "slot machine effect" is one of the most powerful drivers of human behavior. When a reward is unpredictable, it is far more addictive than when it is predictable. Social media feeds use this to great effect. You keep scrolling because you never know when you'll find a truly interesting post or a delightful photo. This variable reward schedule keeps our brains hooked.
5 Psychological Principles You Can Apply Today
You don't need a Ph.D. to start designing for the human brain. Here are five powerful principles from the book you can use right away.
1. Use Social Proof: Don't just tell people your product is great; show them. Prominently display testimonials, case studies, user counts, or reviews to build instant credibility.
2. Employ Progressive Disclosure: If you have a complex form or settings page, hide the advanced or non-essential options behind a link. Reduce the cognitive load on your users to make the experience feel effortless.
3. Guide Attention with Faces: If you use a photo of a person on your landing page, make sure they are looking atyour call-to-action button or key headline, not away from it.
4. Design for Scanners, Not Readers: Structure your content with clear headlines, sub-headlines, short sentences, and bulleted lists. Assume no one will read your beautiful paragraphs from start to finish.
5. Leverage Storytelling: Our brains are wired for stories, not for data dumps. Frame your information within a narrative. A compelling customer success story is far more persuasive and memorable than a dry list of product features.
A Quick Designer's Self-Audit
Use these questions to evaluate your own product, website, or presentation through a psychological lens.
The 5-Second Test: Can a brand-new user understand what your page is about and what they can do there within five seconds, just by scanning?
The Memory Check: Are you forcing your user to remember information from one screen to the next? If so, you are overloading their short-term memory and creating friction.
The Motivation Audit: What psychological principles are you using to encourage a desired action? Are you showing social proof? Is there a clear reason for the user to act now?
The Clarity Check: Is your primary call-to-action (e.g., "Buy Now," "Sign Up for Free") the most visually conspicuous thing on the page? Is the label a clear, action-oriented verb?
Final Reflections
100 Things Every Designer Needs to Know About People is an essential resource that bridges the critical gap between design and psychology. It argues convincingly that the most intuitive, effective, and successful products are born from a deep empathy and understanding of how the human mind operates. By grounding our design choices in the science of human behavior, we can move beyond simply making things that look good and start creating experiences that feel good, connect deeply, and work brilliantly.
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