Free The Design of Future Things by Don Norman Page A

Dave Wroblewski, and Tim McCandless have done just that, adding marks on electronic documents so that viewers can find which sections have been looked at the most. Dirt and wear have their virtues as natural indicators of use, relevance, and importance. Electronic documents can borrow these virtues without the deficits of dirt, squalor, and damage to the material. Implicit interaction is an interesting way to develop intelligent systems. No language, no forcing: simple clues in both directions indicate recommended courses of action.
    Implicit communication can be a powerful tool for informing without annoying. Another important direction is to exploit the power of affordances, the subject of the next section.
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Affordances as Communication
    It started off with an e-mail: Clarisse de Souza, a professor of informatics in Rio de Janeiro wrote to disagree with my definition of “affordance.” “Affordance,” she told me, “is really communication between the designer and the user of a product.” “No,” I wroteback. “An affordance is simply a relationship that exists in the world: it is simply there. Nothing to do with communication.”
    I was wrong. She was not only right, but she got me to spend a delightful week in Brazil, convincing me, then went on to expand upon her idea in an important book, Semiotic Engineering. I ended up a believer: “Once designs are thought of as shared communication and technologies as media, the entire design philosophy changes radically, but in a positive and constructive way,” is what I wrote about the book for its back cover.
    To understand this discussion, let me back up a bit and explain the original concept of an affordance and how it became part of the vocabulary of design. Let me start with a simple question: how do we function in the world? As I was writing The Design of Everyday Things , I pondered this question: when we encounter something new, most of the time we use it just fine, not even noticing that it is a unique experience. How do we do this? We encounter tens of thousands of different objects throughout our lives, yet in most cases, we know just what to do with them, without instruction, without any hesitation. When faced with a need, we are often capable of designing quite novel solutions; “hacks” they are sometimes called: folded paper under a table leg to stabilize the table, newspapers pasted over a window to block the sun. Years ago, as I pondered this question, I realized that the answer had to do with a form of implicit communication, a form of communication that today we call “affordances.”
    The term affordance was invented by the great perceptual psychologist J. J. Gibson to explain our perceptions of the world. Gibson defined affordances as the range of activities thatan animal or person can perform upon an object in the world. Thus, a chair affords sitting and supporting for an adult human, but not for a young child, an ant, or an elephant. Affordances are not fixed properties: they are relationships that hold between objects and agents. Moreover, to Gibson, affordances existed whether they were obvious or not, visible or not, or even whether or not anyone had ever discovered it. Whether or not you knew about it was irrelevant.
    I took Gibson’s term and showed how it can be applied to the practical problems of design. Although Gibson didn’t think they needed to be visible, to me, the critical thing was their visibility. If you didn’t know that an affordance existed, I argued, then it was worthless, at least in the moment. In other words, the ability of a person to discover and make use of affordances is one of the important ways that people function so well, even in novel situations when encountering novel objects.
    Providing effective, perceivable affordances is important in the design of today’s things, whether they be coffee cups, toasters, or websites, but these attributes