Lecture 4 Interaction

The Interaction
•Interaction models
–translations between user and system
•Ergonomics
–physical characteristics of interaction
•interaction styles
–the nature of user/system dialog

Terms of interaction
domain – the area of work under study
e.g. graphic design
goal – what you want to achieve
e.g. create a red triangle
task – how you go about doing it – ultimately in terms of operations or actions
e.g. … select fill tool, click over triangle

Norman’s model
•Seven stages
1.user establishes the goal
2.formulates intention
3.specifies actions at interface
4.executes action
5.perceives system state
6.interprets system state
7.evaluates system state with respect to goal
•Norman’s model concentrates on user’s view of the interface

execution/evaluation loop
•user establishes the goal
•formulates intention
•specifies actions at interface
•executes action
•perceives system state
•interprets system state
•evaluates system state with respect to goal

Example
Norman uses a simple example of switching on a light to illustrate this cycle. Imagine you are sitting reading as evening falls. You decide you need more light; that is you establish the goal to get more light. From there you form an intention to switch on the desk lamp, and you specify the actions required, to reach over and press the lamp switch. If someone else is closer the intention may be different – you may ask them to switch on the light for you. Your goal is the same but the intention and actions are different. When you have executed the action you perceive the result, either the light is on or it isn’t and you interpret this, based on your knowledge of the world. For example, if the light does not come on you may interpret this as indicating the bulb has blown or the lamp is not plugged into the mains, and you will formulate new goals to deal with this. If the light does come on, you will evaluate the new state according to the original goals – is there now enough light? If so, the cycle is complete. If not, you may formulate a new intention to switch on the main ceiling light as well.