In his book The Design of Everyday Things(Basic Books), Donald Norman applied the term affordance to design. The original use of the term goes back to J. J. Gibson, a perceptual psychologist. Gibson used the term to describe the actionable properties of an object. The classic example is that of a doorknob. To humans the affordance provided is the ability to grasp, turn, or pull the handle. In Gibson's view the property did not have to be visible, it just needed to be something the actor (human or animal) perceived as a way to interact with the object. Norman used this term to describe the idea of a perceived affordance for a user interface element. He hastened to add that the perceived affordance on screen elements does not have physical properties, but on some level users will perceive that they can interact with them largely due to convention, terminology, metaphor, and consistency.
There are some issues to consider when using an Affordance Invitation.
An Affordance Invitation plays off of the familiar to provide an invitation to interact. It works since following understood conventions helps introduce new interaction techniques. By bridging new interaction styles with familiar idioms, the user can be led through a sequence of interactions.
Flickr allows users to perform a number of actions with other Flickr users. Anywhere a user's picture is displayed, a set of actions is revealed on mouse hover. The familiar ...