Don Norman is a Computer Scientist, Electrical Engineer, a Doctor of Psychology and a professor of Human Centered Design. He has written The Psychology of Everyday Things (later The Design of Everyday Things) to deal with frustration: the frustration of being unable to operate the most simple of devices. This inability, Norman realized, was not a consequence of his own perceived stupidity, but was a consequence of bad user interfaces, in other words, bad design.
In The Psychopathology of Everyday Things, Norman discusses that objects shouldn't need instruction to be usable. Interfaces should have visibility, that is, we should be able to see what an object is capable of. These visible messages are natural signals and the design that takes advantage of those is natural design.
Natural mapping is an expansion of the concept of mapping, a direct relationship between what is perceived as possible and intention. Natural mapping uses physicality and culture as guidelines for those mappings, making this relationship understandable.
Affordances, without a doubt the most interesting concept discussed in this chapter (and maybe the book) are properties of a given object. They describe what is possible to do with an object and are the attributes that make objects tools: they give purpose. Constraints on the other hand are like anti-affordances: they describe what we cannot do with a given object or the limits of what we can do. Putting all of these concepts together gives us conceptual models, the mental image of an object, all you can and cannot do with it and the relationships between intention and possibility.
He concludes saying that designing for people is all about making good conceptual models (therefore, understanding mappings, affordances and constraints) and making things visible.
In The Psychology of Everyday Actions we learn the 7 stages of action: forming a goal, forming an intention, specifying an action, executing an action, perceiving the world, interpreting its state, evaluating the outcome; rinse, repeat. We also learn of the two Gulfs, the gulf of execution, the distance between the intentions of the user and the actions possible with the object (see mapping) and the gulf of evaluation, the distance between the physical (visual, perceptual) presentation of the object and the intentions of the user (see visibility, affordances).
Norman also speaks of naïveté through Aristotle, mentioning that we tend to hold very simple, and often wrong, explanations for the phenomena around us. Coincidence leads to perceived causality, making us see relations between actions and results when they are not there. He also discusses silence, the insistence in not reporting errors that we believed are caused by ourselves. This conspiracy of silence leads to helplessness, the perception that we are simply unable to complete a task. This can lead to its own cycle, of taught helplessness, where we generalize our inabilities (and our fear of discussing them) leading to the habit of not trying, which leads to a self-fulfilling prophecy (you prove your own perceived inability by failing to even try to succeed).
Knowledge in the Head and in the World is about memory. Memory in the head is that efficiently, easily retrieved knowledge that we acquire by learning. Memory in the world is information like mappings and reminders, the information that is external to us but, after retrieval (seeing, hearing) and interpretation, becomes content that we can also use to act.
These two types of memory allow us to have precise behavior without precise knowledge:
- We don't need all the information to be within our heads, we can retrieve it from the world.
- Precision is unnecessary; as long as we have enough knowledge to distinguish right from wrong, so we can interpret the external information to complete a task.
- The world limits possible actions through natural constraints, so we do not need to know all that is possible/impossible, we can infer through interaction
- Additionally, cultural constraints are carried with us through learning, so we know what is acceptable to do with a certain object.
A design model is the ideas of the object's designer on what can and cannot be done with it. A user's model is that which the user develops through observation of this object and a system image is the totality of information available on a given object (affordances, constraints, instructions, appearance). In an ideal world, the design and user model are identical. The system image should also perfectly align the appearance and instruction set of an object with the real affordances and constraints of an object.
Knowing What to Do expands on constraints by attempting to assemble a Lego motorcycle: physical constraints are true limitations of size, weight, mobility; semantic constraints are limitations based on meaning (the windshield goes in front of the driver, the driver points forward, etc); cultural constraints are about accepted conventions (the red light means stop, goes in the rear; text is to be read, so it must be right-side-up, etc) and logical constraints are limitations in logic (all bike parts must be connected to work, no parts can be missing, etc).
Constraints are as important as affordances to tell us what to do. If constraints are deceiving, we are unable to understand what is really possible with an object. If you can perceive more than one possibility from a single part, you are a victim of bad mapping.
To Err is Human is about making mistakes. The most common type of error is a slip, when we end up doing something when we intended to do another thing. Slips can be capture errors (two sequences start the same and you unconsciously move from one to the other), descriptive errors (we confuse two look-alike objects and do to one what we should do to the other), data-driver errors (we retrieve wrong data and work on this equivocal information), associative activation errors (the event gets a similar, but wrong, response), loss-of-activation errors (we forget what we were doing mid-action) and mode errors (objects with several available modes are used without first selecting the correct mode).
Good design uses feedback to prevent or warn about slips by showing there was a discrepancy between intention and result.
Different levels of complexity are acceptable for different types of tasks:
- Deep tasks cannot be wide, but shallow tasks can (there can be many flavors of ice-cream to choose from without risk).
- Narrow tasks can be deep, but wide tasks can't (when cooking by following a recipe, there can be many steps because there are very little decisions to be made).
Good design deals with human error by understanding and minimizing causes for error, making it possible to undo actions, making errors easy to discover and fix and understanding that tasks are imperfect simplifications of users actions. And if all else fails, designers should resort to locks (forced sequences that prevent users from making mistakes).
The Design Challenge is about designers as human beings. We are at a constant balance between usability and aesthetics and the iterative process of design, analyse for errors and modify (repeat until time/budget/resources run out). We also have limited mental resources and cannot predict everything. Our attention is too focused and too limited. We also are not end users, and most of the times, neither is our client. Lastly, we have a tendency to ignore convention in the name of innovation, sometimes breaking affordances and constraints.
We must also accept that sometimes there are no perfect answers and the best solution is a balance.
Last but not least, the most common design sins: complex is cool or the worshiping of false images and creeping featurism, adding more and more features that add more complexity than utility.
User-Centered Design, the final chapter, is about the philosophy of good design. The chapter revisits every chapter of the book in order to posit what good design actually is.
A good design makes possible actions clear, makes everything visible (actions, results and the conceptual model itself), makes evaluation easy and follows natural mappings between intention and action, action and result and visible information and interpretation. It uses both knowledge in the world and knowledge in the head, it simplifies structure, it bridges the gulfs of execution and evaluation, it gets mappings right, it exploits constraints and it allows for dealing with error.
This was the first time I've read The Design of Everyday Things since my early days of Industrial Design college in 2007. It is one of my two favorite books by Don Norman, together with Emotional Design. Contrary to the opinion of most of my Industrial Design colleagues, I do not think this book is offensive to the profession, but rather a fantastic guide of good, human-centered design. Designers should be less egocentric and understand they are not artists, they are craftsmen who trade in human needs and whose handicraft are useful objects. Re-reading this book made me decide I must read something else Norman wrote between these two of my favorite books, probably Turn Signals are the Facial Expressions of Automobiles.
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