029 Constraint
Limiting the actions that can be performed to simplify use and prevent error.
• There are two types of constraints: physical and psychological.
• Physical constraints limit the range of possible actions by redirecting physical motion. The three kinds of physical constraints are paths, axes, and barriers.
• Psychological constraints limit the range of possible actions by leveraging the way people perceive and think. The three kinds of psychological constraints are symbols, conventions, and mappings.
• Use constraints to minimize errors. Use physical constraints to reduce unintentional inputs and prevent dangerous actions. Use psychological constraints to improve the clarity and intuitiveness of a design.
See Also Affordance • Confirmation • Control • Errors Forgiveness • Mapping • Nudge
