Err is human...

This is my second post based on notes from the book The Design of Everyday Things by Donald Norman. As I mentioned in last post, I loved the chapter about human errors and mistakes and how to design things to avoid this mistakes. So, here are my notes...

There are different types of errors:

1. data-driven errors
2. capture errors
3. description errors
4. associative activate errors
5. lost-of-activate error (forgot what wanted to do)
6. mode errors (forgot in which mode)

It's not always easy to detect errors because:

1. feedback is not always available (lack of visibility)
2. different level of seeing error (you're looking error at more low-level while it's a level or a few above)

The way we think, the knowledge we possess are always important to make or not some slip. For example, based on our experience we can assume different behavior from pressing some button. Culture difference is also another example of such source of slips.

Many mistakes are caused by *social pressure*, when person does not have enough time or power to think and analyze, or enough resources to make a decision.

Designing for Error

Because we all make mistakes and error is inevitable, things should be design with error in mind. Here are some simple rules that are important to follow:

1. Understand the causes of error and design to minimize those causes.
2. Make it possible to revert the actions, or make it harder to do if it can't be reverted.
3. Make it easier to discover errors that do occur, and make them easier to correct.

Basically, good design should:

1. prevent slips before they occur
2. correct them when they occur
3. minimize the impact of done errors.

This means, that controls that can cause serious consequences should be located far away from common controls, they should have different look and way of operation, so they can't be messed up with non-important or easy-to-undo controls.

Although things should be designed to minimize or avoid the errors, it is not always the best thing to constrain the consumer from using product because of possible error. For example, it is generally good you can't run microwave with open door. However, it's absolutely non-acceptable to restring someone from driving if the safe belt is not used. Such forcing features are not always helpful. But there are many examples where they are used in right place and correctly. Forcing feature should force consumer to do thing right, but shouldn't stop from using a thing at all.