Why this book? 
I have been studying design for almost a year now - and I realized that it was high time to finally read one of the Holy Scriptures of Design if you will - The Design of Everyday Things by Don Norman.
As I work my way through this book, I will be taking you along with me on this Journey by summarizing each chapter after I read it. 
What makes design good or bad?
In Chapter One - The Psychopathology of Everyday Things - Don Norman introduces us to some of the basics of good and bad design and helps us to understand how a disconnect between designer and user can cause bad design. 
His introductory example is that of the simple door. Normally, doors don't strike us as objects needing any explanation in order to be used. But Norman illustrates in several somewhat comical examples how an effort to prioritize beauty over utility can cause a complete lack of understanding of whether a door should be pushed, pulled, or slid to be opened. 
He then highlights the two most important characteristics of good design: Discoverability and Understanding. A well-designed product must have some indication of which actions are possible and how they can be performed. While some more complex objects might require some explanation to aid in discoverability and understanding, a simple object should require no instructions to be usable. If the functionality of an object is so intricate and the indications of how it is to be used are so confusing that it cannot easily be learned, the whole purpose of the design is lost, argues Norman. 
We are then introduced to the complexity of modern devices and the separation of design into three distinct fields: 
- Industrial design focuses on the functions, value, and appearance of a product
- Interaction design concentrates on how people interact with technology
- Experience design emphasizes the quality of the all-around interaction experience
Design, according to Norman, is therefore concerned with "how things work, how they are controlled, and the nature of the interaction between people and technology". 
How does bad design cause errors? 
Machines are designed by humans, but contrary to their human users and designers, they lack cognition and will continue to follow a basic set of instructions. If a user does not understand the underlying functionality and gives the machine a faulty command, it will continue to do what it is told, regardless of how illogical the command might be. Engineers, explains Norman, are trained to think logically and sometimes have trouble understanding that users will not always behave in a logical fashion. 
Norman highlights an example of a nuclear power plant accident that was essentially caused by poor design - a minor mechanical malfunction was diagnosed because the machinery could not clearly communicate the error to the workers of the plant. So bad design is not only unhelpful, it can be downright dangerous!
Human-Centered Design
Each new field requires time to adapt to the principles of good design, and extensive study and experimentation are necessary before a new product can function according to good design. In an environment of rapidly advancing technology, this poses a problem for designers. 
The solution: Human-Centered Design. This is a relatively recent design philosophy that puts human needs, capabilities and behavior first, it relies on observation to understand how users interact with a product and what errors might arise. Instead of trying to specify the problem right away, human-centered design delays specification as long as possible and instead focuses on an iterative process of trial and error - every iteration gets closer to the final product by improving on issues that arose in the previous iteration. 
In HCD, communication is vital - especially error communication! "Designers need to focus their attention on cases where things go wrong", says Norman: It is vital to highlight the error and show the user what steps to take to solve it.
Fundamental principles of interaction
When designing a new product, interaction experience is critical, as it determines how enjoyable a product is to use. One very important aspect of good interaction design is Discoverability!
To ensure that the functions of a product are both discoverable and learnable, six psychological concepts need to be appropriately applied to its design:
1. Affordances: An affordance is defined as the relationship between an object and the user interacting with it. Some affordances are perceivable, others might need signifiers to be discoverable.
2. Signifiers: A signifier is a clue that helps users identify affordances - it indicates possible and appropriate behavior when interacting with a  product. Signifiers must be perceivable to be useful.
3. Constraints: Constraints restrict usage of a product to its intended purposes in order to limit errors and avoid accidental misuse of a product for something other than its intention. 
4. Mapping: Mapping is defined as creating a relationship between the elements of two sets of things, for example, the spatial correspondence between the layout of controls and the objects they control. It helps users build a conceptual model of how different elements interact.
5. Feedback: Feedback lets users know the system is working as planned - and also if it isn't. Feedback communicates the results of an action through visual, auditory, or haptic clues. It must be immediate, informative, and specific in order to be useful.  Feedback must be planned and unobtrusive – designers must prioritize feedback by importance so as not to overwhelm the user, causing a "boy who cried wolf" effect, where users are so overwhelmed by feedback that they ignore vital error alerts. 
6. Conceptual Models: Conceptual models are an explanation of how something works, this can be a mental model, an instruction manual, or even inferred understanding through experience. A good conceptual model is created by affordances, signifiers, constraints, mapping, and feedback. 
The Design Challenge
The big challenge about designing great products is the number of different elements that need to be considered as well as all the different interests of designers, engineers, and stakeholders. Good communication is key, says Norman, and he assures us that "It can be done." 

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