In “Affordance, Conventions, and Design, Donald Norman argues that the usability of a device’s design boils down to three major concepts: the model, the constraints, and the affordances. Since the appearance of a device should provide clues for its operation, a designer’s job involves knowing how people relate to an object’s functionality. Affordances refer to the ways in which a thing can be used, and cultural constraints or learned behaviours indicate the limitations of a device when there are no perceived affordances indicating how that thing can and should be used.
In an attempt to explain how constraints and affordances are so closely related, Norman reminds us that designers form conceptual models based on universal behaviors. For example, in a screen design, a cursor that is shaped like an arrow implies that it affords clicking, just as a hand-shaped cursor implies that the user can move or manipulate that area of a screen. If there is no cursor that implies an action, users will likely not try to click or move anything, because cultural constraints are telling them that their actions will do nothing. Norman states that when there is no perceived affordance indicating an action, the conceptual model is not functional and the user will not know what to do.
For Norman, the most important principle in the design of a good conceptual model is visibility, 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, if a door has a handle that affords pulling, the door should open outwards and not inwards. Thus, a 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. Lack of visibility and poor conceptual mental modelling will make an object difficult to use, since people form these models by interpreting the possible ways that they can engage with the device.
By the article’s conclusion, Norman declares that in terms of design principles, affordances are actually of little importance to the users themselves; it is the designer’s job to establish what the user wants in an interface or an object, and how to make it usable and perceivable for them.
Works Cited: Norman, Donald A. “Affordance, Conventions, and Design.” Interactions. (1999): 38-43. Web.