The Motive Web Design Glossary
perceived affordance
Perceived affordance is the quality of an object that suggests how it might be used.
In screen-based communications, the concept of perceived affordance is useful when designing or evaluating a graphical user interface (GUI). To quote user-engineering proponent Don Norman:
Does the user perceive that clicking on that object is a meaningful, useful action, with a known outcome? [1]
(Where ‘object’ is an interface element, such as a button, checkbox or hyperlink.)
affordance (perceptual psychology)
Affordance is a term created by the perceptual psychologist J. J. Gibson to refer to the qualities of the physical world that suggest the possibility of interaction relative to the ability of an actor (person or animal) to interact. McGrenere and Ho presented three fundamental properties of an affordance as defined by Gibson:
- An affordance exists relative to the action capabilities of a particular actor.
- The existence of an affordance is independent of the actor’s ability to perceive it (emphasis added).
- An affordance does not change as the needs and goals of the actor change. [2]
For example, the affordance of a branch as ‘a nice place to sit’ are dependent on:
- the qualities of the branch: how much weight it supports, how high of the ground it is, etc.; and
- the capabilities of the actor: how much they weigh, ability to climb, etc.
Based on the original definition and fundamental properties, affordance, in relation to interface design, relates more to (physical) input devices: mouse, keyboard, stylus, etc. When discussing the qualities of a graphical user interface, the preferred term is perceived affordance.
perceived affordance (user interface engineering)
User-engineering proponent Don Norman used the term affordance in the context of product design, and how the design of an object suggests its use.
When you first see something you have never seen before, how do you know what to do? The answer, I decided, was that the required information was in the world: the appearance of the device could provide the critical clues required for its proper operation. [3]
At this point the term affordance was introduced to the graphical and industrial-design communities. Subsequently Norman has sought to distinguish between the actual (natural, physical) properties of an object and the appearance of affordance by adding the qualifier ‘perceived’.
The designer cares more about what actions the user perceives to be possible than what is true. (emphasis added) [4]
This is what the interface designer should care about: Does the user perceive that clicking on that object is a meaningful, useful action, with a known outcome? (emphasis added) [5]
The perceived affordance an object (or interface element) is determined by factors including:
- context: the environment or process in which the element is displayed;
- culture: the influence of societal ‘norms’ on the individual’s understanding and use of a object;
- instinct: an unconscious association, often linked to phsical characteristics, for example, the size of an object in relation to the human form;
- mental model: the user’s understanding and expectations of interaction with the object.
For example, in the context of a website, the perceived affordance of underlined text is that it indicates a hyperlink; and, that when followed (clicked), the user will link to information that relates to the hyperlinked word or phrase.
GUI, interface, look-and-feel, mine-sweeping, usability, wysiwyg.
References and further reading
- [1], [3], [4], [5] Affordance, conventions and design (Don Norman, Just Noticeable Difference)
- [2] McGrenere, J. and W. Ho, 2000: Affordances: Clarifying and Evolving a Concept. Graphics Interface 2000, Montreal.
- Affordances and design (Clemmer College of Education)
Differences between objective and perceived affordances. The relationship between product design, cultural constraints and cultural conventions. - Affordance theory (Purdue School of Technology)
- Disaffordances and engineering obedience (Dan Lockton, Architectures of Control)
The flip side or companion issue to creating an interface that communicates how something can be used is to create an interface that discourages inappropriate use. For example park benches that look (and are) uncomfortable to sleep on.
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