In addition to thinking about the consequence of errors, as in the Van der Linen study described, there is another usual error taxonomy. The Morrell taxonomy classifies two types of errors: performance and moto-control.
- Performance Errors
  - Performance errors are mistakes you make when you've gone through the steps to complete a procedure.
    - Commission Errors
      - Taking additional steps that were unnecessary
    - Omission Errors
      - You've only set up the outgoing ones. In this case, you omitted steps.
    - Wrong-Action Errors
      - You took an action at the appropriate point in the procedure, but it was the wrong action.
  - Moto-Control Errors
    - Motor-control errors are those you make while using the controls of a device.
    - You may have different errors that you want to track as you design or conduct user testing.
    - The important thing is to decide ahead of time which types of errors you think people will make, and which are important for you to detect and correct.