affordance - Affordance A property in which the physical...

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Unformatted text preview: Affordance A property in which the physical characteristics of an object or environment influence its function. Objects and environments are better suited for some functions than others. Round wheels are better suited than square wheels for rolling; therefore, round wheels are said to better afford rolling. Stairs are better suited than fences for climbing; there- fore, stairs are said to better afford climbing. This is not to say that square wheels cannot be rolled or fences climbed, rather that the physical characteristics of round wheels and fences influence the way they function and are likely to be used.‘ When the affordance of an object or environment corresponds with its intended function, the design will perform more efficiently and will be easier to use. Conversely, when the affordance of an objector environment conflicts with its intended function, the design will perform less efficiently and be more difficult to use. For example, a door with a handle affords pulling. Sometimes, doors with handles are designed to open only by pushing—the affordance of the handle conflicts with the door's function. Replace the handle with a flat plate, and it now affords pushing—the affordance of the flat plate corresponds to the way in which the door can be used. The design is improved. Images of common physical objects and environments can enhance the usability of a design. For example, a drawing of a three-dimensional button on a computer screen leverages our knowledge of the physical characteristics of buttons and, therefore, appears to afford pressing. The popular “desktop” metaphor used by computer operating systems is based on this idea—images of common items like trash cans and folders leverage our knowledge of how those items function in the real world and, thus, suggest their function in the software environment.2 Whenever possible, you should design objects and environments to afford their . intended function, and negatively afford improper use. For example, stackable chairs should only stack one way. Mimic familiar objects and environments in abstract contexts (e.g., software interfaces) to imply the way in which new systems can be used. When affordances are successfully employed in a design, it will seem inconceivable that the design could function or be used otherwise. See also Constraint, Mapping, Mimicry, and Wayfinding. 20 Universal Principles of Design 1 The seminal work on affordances is "The Theory of Affordances" by James Gibson, in Perceiving, Acting, and Knowing by R. E. Shaw & J. Bransford (Eds), Lawrence Erlbaum Associates, 1977; and The Ecological Approach to Wsua/ Perception by James Gibson, Houghton Mifflin, 1979. A popular treatment of affordances can be found in The Design of Everyday Things by Donald Norman, Doubleday, 1990. 2 Note that the term affordance refers to the properties of a physical object or environment only. When images of physical objects or envi- ronments are used (e.g., image of a button), the images, themselves, do not afford any- thing. The knowledge of button affordances exists in the mind of the perceiver based on experience with physical buttons—it is not a property of the image. Therefore, the affordance is said to be perceived. See, for example, “Affordances and Design” by Donald Norman, www.jnd.org. Outdoor lighiirg sir-iiciuree. often ar'i'ortl Ending ant: perching for birds. Where birds. perch. birds [ac-3;). ThIS anti DHH arioilier. perhli iiiiliire i5 d‘flSlgl’iifl-fl in ' 'tach tr.) ' “tunes and rretlLiiL'L- ilie purch- ir'g alfrnrclarhte. Dom alliarclances l-FLfLLILJé-Jnll'f r_'|_v nf'. 3hrin Il'i thi: rliiiir c‘rn llit: lr:."l. Tl "puah" afinrijamc . -::f the C'an i‘s km . iiIJlL‘ Lirin Lit-Cause ol llit.‘ Sign. whiLla (marshals wrll‘. lire powerlul "pull" affor- dryicu 01 l':ir-,‘ huddle. Bv replacing the handle with a flat plate. the confzici is (-llll'illlfiilt-Pd arirl lire: gag-r1 IE-i SlJ[}I-‘.I'liIIDIJF.. 0X0 is well known for the handle designs of llicir producls; ape, cu'mr, and lexiure combine to CFEaEE HTE!‘ sistible grupaing affordannes. With nppnsrng male and female surfaces and featureless sides, Lagos naturally afiorcl [ilLE rig iniri This recessed luulpiates and handlebar orientation Lil I'IIL‘ Seaway I ‘.L:[l!E!-'| Transporter ail-3rd one mounting position {or the L.SF!!'—H‘:E' mrrect nnfi. Ailnrnarce 21 ...
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affordance - Affordance A property in which the physical...

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