Five more design principles informed by psychology
People ignore design that ignores them
In 1988, an Airbus A320 crashed during an airshow in Habsheim, France, killing three people. The accident was not due to mechanical failure, but rather poor interface design. The pilots believed the aircraft was in climb mode, but the system was actually set to idle descent. The cockpit display failed to make this critical difference clear. Important alerts blended into the background and over-automation made it difficult for the pilots to override the system in time. Although the aircraft functioned as engineered, it failed as a user interface. The tragedy highlighted a vital truth: in high-stakes environments, poor design doesn’t just confuse, it kills.
💡 Psychology informs good design
Design is really an act of communication which means having a deep understanding of the person with whom the designer is communicating. - Don Norman
Steve Jobs believed that design isn’t just about how something looks. It’s about how people feel and think as they use it. Great user experiences are grounded in psychology because our decisions, perceptions and emotions shape every interaction. When I design digital products, I keep in mind various design principles.
1. Aesthetic-Usability Effect
The more beautiful something is, the more likely we are to believe it functions well. - Stephen Anderson
💡 Visually attractive products are perceived to be more usable, even if they aren’t. Users are more forgiving of flaws in a system that looks good.
🎬 We should make beautiful products. A clean, modern design can make users more patient and likely to enjoy using our product. I aim to make aesthetically pleasing websites and apps with minimalist design and carefully considered coloured palettes.
2. Goal-Gradient Effect
Rats in a maze will run faster as they approach the food box than at any other point in the run. - Clark Hull
💡 Users are more motivated to complete a task the closer they are to the finish line. A fitness app showing that we are 200 steps off our daily goal spurs us on.
🎬 Visibly show users their progress. Use tools like step indicators or progress bars to keep momentum high and reduce drop-off.
3. Peak-End Rule
We don't choose between experiences, we choose between memories of experiences. And even when we think we're choosing based on the whole experience, we're often influenced by how it felt at its peak and at its end. - Daniel Kahneman
💡 People judge an experience based on how they felt at its most intense moment (the peak) and at its end, not the total sum of moments. This has major implications for onboarding, checkout flows and support experiences.
🎬 Design a strong peak moment, e.g. successful confirmation message, and an uplifting end, e.g. thank you screen. These shape how users remember the experience.
4. Von Restorff Effect
Making something look different is the easiest way to make it memorable. But if everything’s different, nothing stands out. - Steve Krug
💡 The most different item in a group is the most memorable. A brightly coloured Buy Now button stands out because it looks unlike anything else.
🎬 Use visual contrast, through size, colour or shape, to draw attention to our calls to action and important content.
5. Occam’s Razor
Extraordinary claims require extraordinary evidence. - Carl Sagan
💡 When faced with multiple possible designs, the simplest one is usually best. Every added feature or visual element introduces the potential for confusion.
🎬 Strive for simplicity. If something doesn’t serve a clear purpose or enhance the user’s experience, remove it.
🎬 Airbus crash could have been avoided
If you think good design is expensive, you should look at the cost of bad design. - Ralf Speth
The Airbus A320 crash revealed how poor interface design can lead to disaster. Had core design principles been applied, such as Jakob’s Law (aligning with user expectations), the Von Restorff Effect (making critical alerts visually distinct) and Occam’s Razor (simplify the interface), the pilots could have more easily understood the aircraft’s true status. Clearer, psychologically informed design might have prevented the crash, proving that good user experience isn’t just helpful, it can be lifesaving.
Other resources
Why Design is Essential talk by Steve Jobs
Five Design Rules Informed by Psychology post by Phil Martin
Four Icon Design Tips post by Phil Martin
Jony Ive, Apple’s Chief Design Officer, is celebrated for his sleek and stylish designs. He said, Carefully considered design decisions suggest that someone cared.
Have fun.
Phil…
