Errors have two major forms. Slips occur when the goal is correct, but the required actions are not done properly: the execution is flawed. Mistakes occur when the goal or plan is wrong.
Slips and mistakes can be further divided based upon their underlying causes. Memory lapses can lead to either slips or mistakes, depending upon whether the memory failure was at the highest level of cognition (mistakes) or at lower (subconscious) levels (slips).
The Design of Everyday Things: Revised and Expanded Edition
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