Quotes from Donald A. Norman

Logical constraints are often used by home dwellers who undertake repair jobs. Suppose you take apart a leaking faucet to replace a washer, but when you put the faucet together again, you discover a part left over. Oops, obviously there was an error: the part should have been installed. This is an example of a logical constraint.

What appears good in principle can sometimes fail when introduced to the world. Sometimes, bad products succeed and good products fail. The world is complex.

Conventions are actually a form of cultural constraint, usually associated with how people behave. Some conventions determine what activities should be done; others prohibit or discourage actions. But in all cases, they provide those knowledgeable of the culture with powerful constraints on behavior.

the first edition of this book, then called POET, The Psychology of Everyday Things, I started with these lines: "This is the book I always wanted to write, except I didn't know it." Today I do know it, so I simply say, "This is the book I always wanted to write.

Violate conventions and you are marked as an outsider. A rude outsider, at that.

The frequent traveler is continually confronted with this kind of situation: the behavior that is appropriate in one place is inappropriate in another, even in situations that appear to be identical. Known cultural norms can create comfort and harmony. Unknown norms can lead to discomfort and confusion.

The best products come from ignoring these competing voices and instead focusing on the true needs of the people who use the product.

la paradoja de la tecnología: por lo general, una mayor capacidad funcional se ha de pagar con una mayor complejidad.

the impact of competitive forces that drive the introduction of extra features, often to excess: the cause of the disease dubbed "featuritis," whose major symptom is "creeping featurism.

The designer shouldn't think of a simple dichotomy between errors and correct behavior; rather, the entire interaction should be treated as a cooperative endeavor between person and machine, one in which misconceptions can arise on either side.

Standardization is indeed the fundamental principle of desperation: when no other solution appears possible, simply design everything the same way, so people only have to learn once. If

Machines that give too much feedback are like backseat drivers.

Design for individuals and the results may be wonderful for the particular people they were designed for, but a mismatch for others. Design for activities and the result will be usable by everyone.

As a rule, it takes time for information to get into LTM and time and effort to get it out again.

Knowledge in the world includes perceived affordances and signifiers, the mappings between the parts that appear to be controls or places to manipulate and the resulting actions, and the physical constraints that limit what can be done. Knowledge

Affordances determine what actions are possible. Signifiers communicate where the action should take place. We

Knowledge in the head includes conceptual models; cultural, semantic, and logical constraints on behavior; and analogies between the current situation and previous experiences with other situations.

Technology does not make us smarter. People do not make technology smart. It is the combination of the two, the person plus the artifact, that is smart. Together, with our tools, we are a powerful combination.

In theory, there is no difference between theory and practice. In practice, there is.

Affordances determine what actions are possible. Signifiers communicate where the action should take place.

Engineers and businesspeople are trained to solve problems. Designers are trained to discover the real problems. A brilliant solution to the wrong problem can be worse than no solution at all: solve the correct problem.

superb design. Many readers have

The next time you can't immediately figure out the shower control in a hotel room or have trouble using an unfamiliar television set or kitchen appliance, remember that the problem is in the design. Ask yourself where the problem lies.

An interesting property of slips is that, paradoxically, they tend to occur more frequently to skilled people than to novices. Why? Because slips often result from a lack of attention to the task. Skilled people—experts—tend to perform tasks automatically, under subconscious control. Novices have to pay considerable conscious attention, resulting in a relatively low occurrence of slips.