The Design of Everyday Things by Donald Norman
Overview
Design is everywhere; everything is designed. Look around you, somebody at some point made a conscious decision for just about anything: that rim between your cup and saucer, the tag (or lack of) at the back of your shirt, even the upside down squeezy ketchup bottle. And all of this should be designed to provide the best experience for the user. In his book, Norman outlines several foundational principles any designer should follow when creating, building, or simply improving a product.
As a psychologist, I was expecting more psychology terms thrown in, especially since the book’s original title was “The Psychology of Everyday Things.” This average sized, somewhat dense book, can at times be a little repetitive, but it can be quite amusing, as it’s chock full of curious little anachronisms, some scarily spot on predictions, and some suggestions for technology that still doesn’t exist today, but definitely should.
In this post, basic principles will be introduced, with lots of examples, both from the book and from my personal experience (or from spontaneous thought).
“When simple things need pictures, labels, or instructions, the design has failed.” (pg 9)
Design Principles
Conceptual Model
The blueprint that a person holds in their head about how an object works makes up the conceptual model. Thus, we can predict the effects of our actions, knowing what is going to happen before we even try. It is important for the user to hold the correct conceptual model in their heads; otherwise, they may misuse the object, attempt actions that are impossible, or simply not get the most out of it.
To illustrate this point, Norman compares the central AC system with the car’s AC system. In a house, the AC is on or off, hot or cold. On the other hand, in a car there is a mix of hot and cold air at different levels. Thus, the fastest way to cool down a car is to blast the maximum amount of the coldest air until the desired temperature is reached, then adjust to maintain it. But in a house this is not an effective strategy, as setting the thermostat colder than it needs to be will not cool the house any faster.
Another common misunderstanding that comes to mind is to kick something when it doesn’t work properly. We’ve all done this, somehow knowing that it won’t do any good, but at the same time thinking it just might. This is either because kicking it has worked in the past, or, most likely, because our mental model of this object is incorrect, in that we believe that a physical jolt will jiggle the mechanical pieces, shuffling them into their right place again.
Visibility
The quickest method to figure out how something works is to look at it. Thus, it is important to display all the possible actions. I remember I had a gaming console where there was a power button on the front, but there was also a power switch on the back which I always forgot about, as it was not very visible. But visibility isn’t just about seeing everything, it’s about making things salient, distinguishing the stuff a user needs from everything else. On websites, it has become common practice to use menus that appear only when hovered over. While this prevents all the possibilities from being seen at once, it makes the primary actions always visible, while specific subsets of actions are visible only when the user needs them, making it an effective visual system.
Feedback
It is important to indicate the present state of the object, such as whether it is on or off, and a change of state in the object, such as whether the coffee machine stopped brewing and the coffee is now ready. The consequences of our actions should be clear: when I pushed that button, the machine made a bleep, or a tiny light flashed, letting me know that it is now on. Feedback can be visual, auditory, or both, and can be persistent or temporary, and can be general or specific. Think about all the possibilities of providing feedback on a web form: when the user makes an error filling out a field, you can flash a message with a precise text explanation of the error, have that message fade but keep the field highlighted in red, and maybe even make a beep if the user tries to submit an invalid form.
Constraints
Physical constraints are the most salient, often perceivable immediately by sight.
Think about the toy you played with as a toddler where you placed large shapes into the similarly shaped holes: you probably realized at some point that a square object does not fit into a round hole. Errors are easily prevented, since incorrect actions are nearly impossible. Size, orientation, color, texture are all physical markers. For a web example, think of a button that is disabled when it would not be correct to push it, such as preventing submission of an incomplete web form. Semantic constraints are based on purpose; for instance, Norman points out that it doesn’t make sense for a motorcycle rider to sit facing backwards. There are also logical constraints, such as a one-to-one spatial mapping of the stove knobs with the stove burners. Cultural constraints are based on societal rules and norms. Although often arbitrarily established, they are ingrained in our thought and behavior, guiding us in both novel and familiar situations. For instance, we expect a door to have a handle of some sort at a certain height on the door itself, unless it opens automatically. Confusion can arise when this pattern is broken — say, a door that opens by pushing a button on an adjacent wall — and a person then needs to figure out how to operate the door.
Constraints limit possible actions, while affordances show the possible actions.
Affordances
Affordances are those properties of an object which intuitively call to be used in a certain way —a button “wants” to be pushed, a knob “wants” to be turned, a handle “wants” to be gripped, a switch “wants” to be flipped. Affordances makes the desired action obvious. Shapes, their orientations, materials, and even conventions can turn into affordances: paper affords to be written on, and on the web, text that is underlined and blue affords to be clicked.
Mapping
The relationship between the control and the action is a mapping. In mathematical terms, it is a function, where the domain is the trigger, the range is the consequences of the trigger. Ideally, there should be a one-to-one mapping of control to action. Sometimes this is not possible given the size of the object compared to the number of possible actions, such as a small object with a lot of actions. The stove—a favorite example of Norman, and myself—always has a mapping of knobs to burners, and curiously, this mapping never seems to be right. Usually the knobs are laid out on one thin row, while the burners are in a rectangular array of 2×2 or 2×3. The reason for this could be because the control bar where the knobs are is too narrow to hold two rows of knobs; however, in most modern stoves this is not the case, as there is more than enough space to lay out the knobs in the same layout as the burners. Why this hasn’t been designed otherwise is a mystery to me.
Take the keyboard on my Macbook as another example. The top row has f buttons (f5, f6, f7 etc). These buttons are also labeled with symbols for brightness, volume, pause/play, etc, which are the actual actions mapped to these buttons. So how can you call the “f1″ action? Well, it took me 4 years of using a mac laptop (and I am supposed to be a computer scientist) to realize that by pressing the “fn” key, the “f” buttons could actually be called. Now, some may call this mapping unsuccessful. But would I have liked instead a whole extra row of “f” buttons on my laptop? Probably not. The need for an “f” button was not great enough to drive me to investigate it, I got around fine without them for 4 years, and still after discovering them I only use them sporadically. Is there a better design for this mapping? Probably, there is always room for improvement.
Psychology
Mental Models
Humans form explanatory theories of just about everything. Through trial and error and social learning we have developed mostly correct theories about a lot of things. But children’s mental models are often inaccurate, mostly because they do not have enough experience in the world to have discovered how things actually work (think of the birds and the bees…). The same is true for adults (or any person) trying out a new product or in a novel situation. Where we have no prior experience, whether direct or indirect, we have no mental model. So we are prone to form inaccurate mental models of these at first. Moreover, these inaccuracies may never be corrected if our trial and error doesn’t make it obvious, or if nobody tells us otherwise.
We are always seeking the reasons, the causes for a given effect. Sometimes, when an effect is paired with another event enough times, we may erroneously attribute that event as the cause, even though it could have been pure coincidence for that event to have occurred before the effect a few times. We become superstitious. For instance, who has not seen clicking on a web button repeatedly? It really only re-sends the http request, restarting the entire process each time it is clicked. But most people do not know this, and since it seemed to work the last time… And even those of us who do hold the correct mental model are still guilty of doing this (myself included), possibly because we used to do it when we didn’t know any better, or possibly because we have seen it work before, so it might just work this time.
Thus, it is important to convey an accurate model of how the object works. We can achieve this by building on existing mental models through analogues or metaphors, and avoid confusion among similar but erroneous models. Hints such as diagrams, or specific constraints, can also point to the correct model.
Pluralistic Ignorance
When everybody has the same thought, but is afraid to speak up because they think nobody else has the same thought, and they think this precisely because nobody has spoken up, we have the phenomenon of pluralistic ignorance. Thus, when something is difficult to use, but nobody appears to be having difficulty, we blame ourselves, thinking we must be the only ones having trouble, when in fact everyone has trouble with it. Users may become technophobic, or refuse to seek help in an instruction manual or customer service, for fear of appearing dumb, and thus may never really enjoy, or even use, the product. This is especially true of seemingly simple things.
The Gulfs
The Gulf of Execution is the distance between intention and action. For publishing content on the web, this gulf is continually narrowing with the increasing multitude of sites that automatically set up an entire blog for you in a few simple steps.
The Gulf of Evaluation is the effort to determine state of object, and whether intention resulted in a successful action. Flip the switch and lights go on: the gulf of evaluation is quite small. Flip the switch and lights don’t go on: now the gulf has widened, since you have no way of immediately knowing what is wrong with the light, why it won’t turn on.
Knowledge in the Head and in the World
Not everything has to be detailed on the product; some instructions, tasks, and sequences can be learned and memorized. Conversely, not everything has to be memorized; some things will require constant reminders.
For example, I bet most of you can touch type without looking down on the keyboard. This is knowledge in the head (more specifically, this is procedural knowledge, where it becomes automatic through practice). Your hands know exactly where each key is faster than your head does, which is precisely why you would probably take a lot longer to actually draw out an accurate keyboard from memory. You would probably go through hand motions in the air to help determine which keys are where. And even then, the least used keys, such as ~ or { } you might not get right.
Also, precise information is not required; you only need enough detail to differentiate between one thing and another. For instance, you only need to know the rough size and color of a penny to differentiate it from a nickel; you don’t need to know the exact orientation of Lincoln’s head and what the text above him says.
To find the balance between knowledge in the head and in the world, it helps to know a bit about memory. There are three categories of memory: arbitrary, which is learned by rote; relationships, learned by associating existing knowledge with new knowledge; and explanatory, learned by using a mental model. The last category is the most powerful, as once we understand how something works, we can figure out how to perform any action when it becomes necessary. This means we do not have to memorize the sequences for every possible behavior, but can obtain it if we so desire.
Errors
One type of error is a slip, which are automatic, unconscious errors. These are errors of habit. They can be the continuation of an incorrect action, like driving home instead of the supermarket, or from confusing common association, like turning a pen around and trying to erase with it. Slips can arise from a lack of constraints, from sudden changes to familiar things, or from distractions. On the other hand, mistakes occur much earlier in the process, when a person has chosen the wrong goal. Thus, the intention is erroneous the begin with. This type of error can easily arise from over-generalization, taking existing experience and applying it incorrectly to a novel situation that on the surface looks quite similar. Mistakes come from incomplete or misleading information.
As designers, our primary goal is to prevent errors in the first place by eliminating the cause. Alas, errors happen, so our next goal is to make it easy to recover from errors, by making errors visible through appropriate feedback, as well as by making them easily reversible. Also, remember that errors are sometimes good, or even necessary, for a pleasant user experience. Often part of the fun is in exploring and figuring things out, from a puzzle to a new gadget.
User Centered Design
There are three different conceptual models of an object: the mental model of the designer, the system image or the ‘real’ model, and the mental model of the user. These three should approximate equality. However, it is the designer’s job to effectively communicate an accurate system image to the user. Just remember, designers are most often not the average user. Moreover, there has to be a reason for every design, a function which follows one or several of the design principles. Use constraints, natural, logical, and cultural mappings, design for error, and simplify. And, “when all else fails, standardize.” As Norman points out with the cunning example of a clock, which has the numbers in ‘counter-clockwise’ order, some conventions cannot be broken.
User centered design is “a philosophy based on the needs and interests of the user, with an emphasis on making the products usable and understandable.” (pg 188)
Norman Doors
No discussion about this book is ever complete without the mention of Norman Doors, and even Donald Norman himself agrees with this. So here is one experience of mine with Norman Doors.
I was at the back of a coach bus observing the bathroom door. I thought, “this door handle is very well designed. The door handle is a circular inset, with a horizontal bar (see pic). You can’t push the bar like a lever, you can’t pull it, and since it is set inside a circle the obvious affordance is to twist.” Remarkably, it took the 7 people who walked up to it at least 3 tries before getting it right. Some of them even flashed me looks of desperation, their eyes pleading for a hint (but I remained the passive observer). This also inadvertently highlights why user testing is so important: something that seemed obvious to me was very difficult for everyone else.
“Somehow, when a device as simple as a door has to come with an instruction manual—even a one-word manual—then it is a failure, poorly designed.” (pg 87)
Book Information
Title: The Design of Everyday things
Author: Donald A. Norman
Published: 1988, 2002
Pages: 257, black and white
The main image for this post is from Flickr user Agent Smith
Feel free to support, analyze, criticize, and correct any of the above. My primary objective is always to learn.
Tags: design of everday things, donald norman, norman doors, usability, ux
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Thanks for sharing this! It’s very helpful. This book has been on my reading list for awhile, but I haven’t had a chance to buy it yet. Looks like it’ll be worthwhile!
Wow what u wrote realli made my day! (ok i know you’ll think im a retard haha!) good flash