User slips

Rates of user slips. A user slip is a user action that does not suit the user’s intention. Users are fault generators, extensively producing typo errors and mental errors. About 5% of the keystroke-level user actions are inadvertent. The rate of mental slips depends on the task complexity, and is typically much higher.

Effects of user slips. User slips are a primary cause for exceptional states, therefore a main trigger of interaction faults. Several examples of interaction faults described above are triggered by user slips:

• The crash of Torrey Canyon in 1967

• The Therac-25 overdose accidents between 1985 and 1987
• Production waste
• Cable TV setup mishaps

Slip enablers. User slips are enabled by mental workload, due to misinformation, operational complexity and the provision of many options. Options are a main source of inadvertent errors. Misinformation is a main source of mental slips.