Norman Chapter 4 Knowing What To Do Jeff Offutt http://www.cs.gmu.edu/~offutt/ SWE 205 Software Usability and Design

People Expect Simplicity When a task is simple, people expect a simple UI Making a phone call is simple Devices that do a lot of things are harder Multi-purpose devices The most common action should be the easiest to find It is okay for rare actions to be harder When we encounter a new device, we either : transfer knowledge of how to use a similar device or seek instructions 11-Nov-18 © Jeff Offutt

Syntactic Signals The UI design must explicitly indicate what should be done Physical or syntactic constraints limit our actions Affordances of controls—that is, the controls look familiar Down arrows look like drop downs “B” looks like bold face If the UI design matches the user’s mental model and offers good controls, users will not need help 11-Nov-18 © Jeff Offutt

Doors & Switches Dozens of ways to open doors A sign on a door that tells us how to open it is a very short instruction manual If a simple device needs a manual, the UI is a failure Doors on the Paris subway do not open automatically Switches have two basic problems Which switch controls which function (grouping) ? Which switch controls which device (mapping) ? 11-Nov-18 © Jeff Offutt

Door Opening Confusion A push bar for an emergency door … This is much clearer When under stress, people revert to stereotypes But which side to push ? 11-Nov-18 © Jeff Offutt

My Very Own “Norman Door” How do you open it? 11-Nov-18 © Jeff Offutt

Light Switch Device Confusion My parents’ house, 1964-2014 Light arrangement on the ceiling Light switch arrangement one Light switch arrangement two Kitchen Porch 11-Nov-18 © Jeff Offutt

Summary: Visibility and Feedback Make relevant parts visible Feedback Give each action an immediate and obvious effect 11-Nov-18 © Jeff Offutt