affordance

=Affordance=

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Introduction
Affordance, under the definition of design and usability principles, refers to an object's characteristics which enables it to "intuitively imply its functionality and use" (Usability First, 2005) through its sensory characteristics. It was originally termed by perceptual psychologist J. J. Gibson as the "actionable properties between the world and an actor" (Gibson 1977, 1979). According to Gibson, affordances are relationships (Gibson 1977, 1979) which lead users to recognize that a certain action can be accomplished with certain objects. In that sense, product designers are concerned primarily with how the perceived characteristics of a particular product can result in the user to establish a sense of how that product can perhaps be used (Donald, 2002).

Examples
A simple everyday example entails a light switch, pointing to either an upward or downward direction, which suggests the idea of flicking it to the opposite direction. Another common example is a door knob, with its smooth curves and rounded shape which is sized to fit the human hand, suggests the action of turning it one direction or the other. To exemplify how the word affordance can be used to describe a relationship, a simple button can be brought into play; a button which encourages pushing affords this action by being built so that it is elevated somewhat above the surface.

The concept of affordance has been taken into careful considerations in the past two decades since Don Norman's introduction of it to help with the design of everyday things (Elara - David Gelb). At the heart of affordance is the idea of designing an object which makes it appear as obvious as possible to the user how it should be used; for instance, designers should design chairs that easily affords sitting on and oven dials should be designed in a way that affords turning.

Real versus Perceived Affordances
It is also worth mentioning that there are two types of affordances. The first type is referred to as real affordance and is applied to tangible objects such as a cupboard levers and jar lids. Real affordances exist naturally in humans and require no learning (Elara - David Gelb), as opposed to the second type of affordance: perceived affordance. This type of affordance deals with how an object is able to let the user perceive, through its quality, the possible ways in which it could be used, disregarding its "real" properties. Norman maintains that designers should pay particular attention to what actions the user "perceives to be possible than what is true" (jnd.org, 2004). Perception affordance is commonly applied to screen-based interfaces where knowledge about the using object is not totally innate. For example, designers should let the user perceive that clicking on an object on the computer screen is a "meaningful, useful action, with a known outcome" (jnd.org, 2004). Perceived affordance is primarily what designers are concerned with nowadays.