Kaleidocycle

Based on the International Standards Organisation's categories of "effectiveness, efficiency and satisfaction," the author determines ways in which usability can be quantified. 'Effectiveness' is the capacity for a product to generate (or enable) output; 'Efficiency' is measured as the level of effort invested in completing an action or task (for example, the author categorizes usability errors as distinguished between a 'slip' and a 'mistake' in user performance and experience. For him, a slip is when a user accidentally performs the wrong action which is readily corrected by the user, whereas a mistake is when a user thinks he is doing the right thing (intuitive action), but is unable to perform his task.

In "Interacting with Paper," Bill Buxton proposes paper prototyping which he calls 'paper interfaces' as an alternative and a better solution to testing user experiences before starting the design process. The author suggests that paper holds powerful affordances that represent systems of control that users respond to and experience, both in terms of a sketch's control over users' actions (control commands) as well as its faculty to lead users to focus on the 'experience' and 'usability' of an interface rather than on its aesthetic feel or design.