Affordances

I find what Gibson has concluded fascinating. He states; “…the affordances of the environment are what it offers the animal, what it provides or furnishes, either for good or ill. [5, p.127]” In this case WE are the animals and the natural environment that we are given is the computer interface (speaking in terms of the most common interface that we are using in our daily lives or at lease in this instance.) The natural boundaries that we are given are that of the lines, buttons and boundaries of the screen we look at. 

He goes on to say that, "The affordance does not change as the needs and goals of the actor change." In this case I (or we) am the actor. But the difference is that as an "actor" using the computer interface we are constantly changing the look, shape, and direction of the screen. This does not happen without work - that is moving our hands to control the mouse or keyboard to manipulate the screen. Gibson defines this as "environment mutuality." 

Norman's approach to affordances is slightly different. He does to believe that there is an inherent trait or use for the affordance he states, "...that perception by an individual may be involved in characterizing the existence of the affordance." that is that a chair may be picked up and that sitting in the chair may be this most obvious trait but not necessarily the only one. Norman does not believe that there is an importance of an "actor" That the affordances come only from the object. An important point relating to interface design; Norman believes, "that when designers take advantage of affordances, the user knows what to do just by looking." Gibson's ideas seem to be more black and white whereas Norman can identify the shades of grey. 

Other more contemporary theorists such as Gaver and Johnson give more varying definitions of affordance, but the more simple and direct approach to this seems to be the best. It seems like Norman agrees; “Sloppy thinking about the concepts and tactics often leads to sloppiness in design. And sloppiness in design translates into confusion for users. [18, p. 41]”

Speaking about nested affordances ; they are the layers or possible uses of an object or interface . When making shortcuts on a computer interface for example - adding a key command such as (control V) on a MAC to paste - this makes the affordance faster, therefore easier. 

Because the definition of affordances has such a wide meaning, it has almost become lost. Getting back to the most basic definition can help us in designing better interfaces. It seems like Gibson's can be the best because it has the most direct and minimal meaning.

Excerpts from Affordances: Clarifying and Evolving a Concept

Joanna McGrenere

Department of Computer Science

University of Toronto

Toronto, Ontario

Canada M5S 3G4

joanna@dgp.toronto.edu

Wayne Ho

User-Centered Design

IBM Software Solutions Toronto Laboratory

1150 Eglinton Ave. East, Toronto, Ontario

Canada M3C 1H7

who@ca.ibm.com