Computing With Class - The Chocolate Factory Affordance Lesson
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Do doors normally open inwards or outwards into corridors?—and why?

Doors are very simple objects. Complex things may need explaining, but simple things should not. When simple objects need pictures, labels, or instructions, then design has failed.

Purpose of Activity

The aim of this activity is to raise awareness of human interface design issues. Because we live in a world where poor design is rife, we have become accustomed  to putting up with problems caused by the artifacts we interact with, blaming ourselves (“human error,” “inadequate training,” “it’s too complicated for me”) instead of attributing the problems to flawed design. 
What does this have to do with Computer Science?

The key concept here is what are called the affordances of an object, which are its visible features—both fundamental and perceived—whose appearance indicates how the object should be used. Affordances are the kinds of operation that the object permits, or “af- fords.” For example, it is (mostly) clear from their appearance that chairs are for sitting, tables are for placing things on, knobs are for turning, slots are for inserting things into, buttons are for pushing. And computers are for ... what? They have no affordances that indicate their functionality, apart from very low-level ones such as input (e.g. keyboard) and output (e.g. screen) capabilities. 

The great chocolate factory is run by a race of elf-like beings called Oompa-Loompas.1 These Oompa-Loompas have terrible memories and no written language. Because of this, they have difficulty remembering what to do in order to run the chocolate factory, and things often go wrong. Because of this, a new factory is being designed that is supposed to be very easy for them to operate. 

The first problem the Oompa-Loompas face is getting through the doors carrying steaming buckets of liquid chocolate. They cannot remember whether to push or pull the doors to open them, or slide them to one side. Consequently they end up banging into each other and spilling sticky chocolate all over the place. The children should fill out the “doors” worksheet. More than one box is appropriate in each case. For some of the doors (including the first one) it is not obvious how to open them, in which case the children should record what they would try first. Once they have filled out their own sheets, have the whole group discuss the relative merits of each type of door, particularly with regard to how easy it is to tell how it works, and how suitable it would be to use if you are carrying a bucket of hot chocolate. Then they should decide what kind of doors and handles to use in the factory.

Follow this activity with a class discussion. Real doors present clues in their frames and hinges as to how they open, and there are conventions about whether doors open inwards or outwards. Identify the kinds of door handles used in your school and discuss their appropriateness (they may be quite inappropriate!) Do doors normally open inwards or outwards into corridors?—and why? (Answer: They open into rooms so that when you come out you won’t bash the door into people walking along the corridor, although in some situations they open outwards to make evacuation easier in an emergency.) 

With apologies to Roald Dahl. You’ll know about the Oompa-Loompas if you’ve read his wonderful tale Charlie and the Chocolate Factory. If not, never mind: the plot is not relevant to this activity. 

Technical Terms:

Interface design
Transfer effects
Population stereotypes
User interface evaluation

Share With Us
Tweet pictures of doors you've found as you complete the activity! 
More advanced Human Computer Interaction concepts: The Strooping Effect. 
Other Resources
Carnegie Melon Affordances (PDF) 
- Affordance Examples
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