Week 4 - by Alice Low Soo Ying

Lecture for this week is about affordance. Affordance is a term created by the perceptual psychologist J. J. Gibson to refer to the qualities of the physical world that suggest the possibility of interaction relative to the ability of an actor (person or animal) to interact. 

McGrenere and Ho presented three fundamental properties of an affordance as defined by Gibson:

• An affordance exists relative to the action capabilities of a particular actor.

• The existence of an affordance is independent of the actor’s ability to perceive it (emphasis added).

• An affordance does not change as the needs and goals of the actor change.

For example, the affordance of a branch as ‘a nice place to sit’ are dependent on:

• the qualities of the branch: how much weight it supports, how high of the ground it is.

• the capabilities of the actor: how much they weigh, ability to climb.

Based on the original definition and fundamental properties, affordance, in relation to interface design, relates more to (physical) input devices: mouse, keyboard, and stylus. When discussing the qualities of a graphical user interface, the preferred term is perceived affordance.

Perceived Affordance

• context: [where] the environment or process in which the element is displayed;

• culture: [society] the influence of societal ‘norms’ on the individual’s understanding and use of a object;

• instinct: [unconscious] an unconscious association, often linked to physical characteristics, for example, the size of an object in relation to the human form;

• mental model: [expectations] the user’s understanding and expectations of interaction with the object.

Forcing Functions

• Lock in: User cannot exit an operation until a certain condition is met.

• Lock out: Makes starting some operations difficult.

• Interlock: Combines elements of lock-ins and lock-outs.

In conclusion, affordances reflect the possible relationships among actors and objects: they are properties of the world. Designers can invent new real and perceived affordances, but they cannot so readily change established social conventions.

References:
http://www.motive.co.nz/glossary/perceived-affordance.php
http://architectures.danlockton.co.uk/category/forcing-functions/