Affordance, a term first conceptualized by J.J. Gibson, is used to refer a type of relationship that naturally occurs between an inanimate object and a person or animal. In this article, Norman refers to affordance as the actual and perceived use of a thing, and when affordances are taken advantage of, the user knows what to do by just looking at the object and does not have to consciously think about its operability. Norman argues that the appearance of a device provides critical clues for how the human mind can operate it, and the designer’s job involves knowing the psychology of people in relation to how things work. In his book The Psychology of Everyday Things, Norman argues that operating a device boils down to three major concepts: the conceptual model, constraints, and affordances. Norman begins by describing a “perceived affordance,” which is what the user of an object perceives to be possible insofar as the object’s use, and is not necessarily based on what is actually possible. In product design, Norman states that there are both perceived and real affordances, and that these two do not have to be the same. For example, with interfaces, there are real, built-in physical affordances such as the keyboard, screen, and pointing device, which affords clicking, looking, and touching. A perceived affordance in this case would be the assumption that you can operate the screen by touching it – this is regardless of whether the screen is built to be touch-sensitive or not. This affordance exists independently of what is actually possible in terms of the screen’s capabilities, and Norman states that these perceived affordances can actually be useful even if the system does not really support that affordance, because they indicate the object’s visible operations. If affordances are the actual and perceived ways a thing can be used, constraints concern the limitations of the things or how the thing cannot be used. In the latter half of the article, Norman observes that cultural conventions and learned behaviors greatly affect both real and perceived affordances. For example, a cursor that is shaped like an arrow implies that it affords clicking, but a user can actually click anywhere. The fact that the cursor changes into a hand shape when hovering over a certain area is a convention that implies the user can move or manipulate that area of a screen. Norman states that when users do not click on an area that has no cursor, they are acting out of a cultural constraint and the perceived affordance that tells them their clicking will do nothing. Furthermore, when designers work on a screen layout, they rely on the conventional interpretation of symbols as well as behavioral constraints that are physical, logical, and cultural. Norman states that physical constraints and real affordances are closely related, i.e. is it impossible to move a cursor outside of the screen area. Logical constraints relate to good conceptual models, as they rely on reason and are used to guide behavior. One example Norman mentions is the idea that a user will know how to scroll down a page because they can see that it is cut off and that there is a bar on the side that slides. Lastly, cultural constraints are collectively understood; the scroll bar is universal and all users understand that they must drag it downward in order to see the rest of the page that is “off screen.” Norman reminds us that two of the most important principles of design are visibility and natural design, both of which can be done through mapping. Mapping refers to the relationship between two things, or between the controls and their results. For example, if we turn a car steering wheel to the right, the car moves to the right. Or, when a scroll bar that moves a page downward is indicated by a horizontal line instead of a vertical one. Natural mapping takes advantage of physical analogies and cultural standards, which lead to immediate understanding. Thus, device is easier to use when the set of possible actions is visible and the controls exploit natural mapping that has been catered to the user. Norman also mentions that lack of visibility and poor conceptual mental modeling will make an object difficult to use. By mental modeling Norman is referring to the models people have of themselves, others, the environment, and the things with which they interact. Thus, the mental model of a device is formed by interpreting its perceived, possible actions and its visible structure. As the article comes to a close, Norman reiterates that symbols and constraints are not the same as affordances, for they are merely examples of conceptual models, feedback, and conventions that make a design function. Affordances are actually of little importance to the users, and it is the designer’s job to establish what the user wants in an interface and how to make it usable and perceivable for them.
Works Cited: Norman, Donald A. “Affordance, Conventions, and Design.” Interactions. (1999): 38-43. Print.