Don't confuse affordances with conventions. 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.
The theory of affordances. The Ecological Approach to Visual Perception. Usability engineering . Usability inspection methods. T he Psychology of Everyday Things.