To continue my exploration, I recently read Designing with the Mind in Mind: Simple Guide to Understanding User Interface Design Rules by Jeff Johnson (Amazon Link). Like most of the design books that I have, this one is fairly short (under 200 pages), but it is packed with lots of useful information.
This book is primarily about how humans perceive the world, and how we can use that to our advantage when building our user interfaces. It also uses studies about how memory, recognition, and process affect how we interact with the world.
The chapter titles themselves are a list of how humans work:
- We Perceive What We Expect
- Our Vision is Optimized to See Structure
- We Seek and Use Visual Structure
- Reading is Unnatural
- Our Color Vision is Limited
- Our Peripheral Vision is Poor
- Our Attention is Limited; Our Memory is Imperfect
- Limits on Attention Shape Thought and Action
- Recognition is Easy; Recall is Hard
- Learning from Experience and Performing Learned Actions are Easy;
Problem Solving and Calculation are Hard
- Many Factors Affect Learning
- We Have Time Requirements
In each chapter, Johnson gives specific examples of these traits and how our application design can play on the strengths and weaknesses of each. Here are few that stuck out to me.
Chapter 2 ("Our Vision is Optimized to See Structure") covers the Gestalt principles of human perception. Apparently, these are fairly widely-known (and I've recognized some of them in my own design work), but this is the first time I've seen them delineated.
For example, the Proximity principle states that relative distances between objects determines how we group them mentally. Look at the following picture.
We tend to see the blue stars as 3 rows, and we tend to see the orange stars as being in 3 columns. We can use this in our UI design to make sure that things that go together are actually perceived as belonging together.
The Continuity principles states that we often perceive things as continuous even if it's broken in the middle. As an example, we'll consider a slider bar (this one is from Windows Media Player).
The volume slider is made up of 3 parts: the blue line on the left, the circle in the middle, and the grey line on the right. But the tendency of our brain is to see a single line with the circle on top of it. Now, whoever designed this particular slider added something to enhance this perception. Notice that the circle has a dark line going through the middle of it. This gives the added perception that the circle is semi-transparent, and we are seeing the continuous line underneath it.
The other Gestalt principles (similarity, closure, symmetry, figure/ground, and common fate) all have similar examples.
These principles seem obvious once you see them stated. But unfortunately, this chapter also contains several examples of applications that do not follow these principles, which leads to difficulty in using them.
How Fast Does Our Brain Work?
Another chapter that I found especially interesting was Chapter 12 ("We Have Time Requirements"). This takes a look at how long it takes the brain to perceive things, how long it takes us to process information, how long our attention is really dedicated to a single task, and so forth.
The chapter contains an interesting list of perceptual and cognitive functions and the duration of each. This includes things like the shortest gap that we can detect in sound (1 millisecond), minimum noticeable lag in ink as someone draws with a stylus (10 milliseconds), the time required for a skilled reader's brain to comprehend a printed word (150 milliseconds), duration of unbroken attention to a single task / "unit task" (6-30 seconds), and time to choose a lifetime career (20 years).
The most interesting part has to do with the time of a "unit task". This is covered quite extensively. Unit tasks are small (such as filling in login information). We will dedicate 6-30 seconds to a task before our brain jumps away. Now, it may jump right back, or it may get distracted by something else. Our goal as application designers is to try to keep our tasks within this time window.
For example, rather than having someone fill out an entire tax form in one big scrolling screen, we should break this process down into smaller tasks in a wizard-type interface. This allows us to concentrate on one small task at a time. When we click "Next" our brain may wander (or take a quick breather), but we're right back to concentration on the next task.
We looked at just 2 of the chapters here. But I found each chapter interesting. I learned quite a bit about how the human mind works. And more specifically, how I can apply that knowledge to how I design my applications.
I know that my personal web site is in pretty bad shape right now (especially the home page). But this book helped me pinpoint several specific problems. I've been planning on updating things for a while, but this will give me the push to do it in the (hopefully) not-too-distant future.
Designing with the Mind in Mind is a great book for anyone wanting to better understand their users (and how their brains work). Once we understand our users, we are better prepared to create excellent experiences for them in our software.