Affordance, Conventions and Design
http://jnd.org/dn.mss/affordances-interactions.html

Norman, Donald A.
JND.org
1999

Abstract:

Please don't confuse affordance with perceived affordances. Don't confuse affordances with conventions. Affordances reflect the possible relationships among actors and objects: they are properties of the world. Conventions, on the other hand, are arbitrary, artificial and learned. Once learned, they help us master the intricacies of daily life, whether they be conventions for courtesy, for writing style, or for operating a word processor. Designers can invent new real and perceived affordances, but they cannot so readily change established social conventions. Know the difference and exploit that knowledge. Skilled design makes use of all.