Affordances — the first UX Knowledge Base Sketch
Definition by Donald A. Norman
“[…]the term affordance refers to the perceived and actual properties of the thing, primarily those fundamental properties that determine just how the thing could possibly be used. […] A chair affords (“is for”) support and, therefore, affords sitting. A chair can also be carried. […] Affordances provide strong clues to the operations of things. Plates are for pushing. Knobs are for turning. Slots are for inserting things into. Balls are for throwing or bouncing. When affordances are taken advantage of, the user knows what to do just by looking: no picture, label, or instruction required. Complex things may require explanation, but simple things should not. When simple things need pictures, labels, or instructions, the design has failed.” [Donald A. Norman, The Design of Everyday Things, 1988, p9]
However, it needs to be mentioned, that in the Revised and Expanded Edition of the book, Norman added to concept of signifiers as well:
“The first edition had a focus upon affordances, but although affordances make sense for interaction with physical objects, they are confusing when dealing with virtual ones. As a result, affordances have created much confusion in the world of design. Affordances define what actions are possible. Signifiers specify how people discover those possibilities: signifiers are signs, perceptible signals of what can be done. Signifiers are of far more importance to designers than are affordances.” [Donald A. Norman, The Design of Everyday Things: Revised and Expanded Edition, 2013, pXIV-XV]
Norman explains the difference between an affordance and a signifier using a UI design example:
“Soon designers were saying such things as, “I put an affordance there,” to describe why they displayed a circle on a screen to indicate where the person should touch, whether by mouse or by finger. “No,” I said, “that is not an affordance. That is a way of communicating where the touch should be. You are communicating where to do the touching: affordance of touching exists on the entire screen: you are trying to signify where the touch should take place. That’s not the same thing as saying what action is possible.” [Donald A. Norman, The Design of Everyday Things: Revised and Expanded Edition, 2013, p13–14]
Norman, D. A. (2013). Design of Everyday Things: Revised and Expanded, Chapter 1.
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