Violation — deviating on purpose despite knowing the rule

What it is

A violation is a failure where the user clearly knows the correct rule or standard procedure — and is capable of following it — yet deliberately chooses to do something else instead. It differs from both a slip and a mistake: a slip means intending correctly but executing off-plan; a mistake means not knowing the correct action at all; a violation means knowing it, being able to do it, and choosing not to, based on some trade-off.

Why it happens

A violation doesn't occur at the level of knowledge or execution — it occurs at the level of motivation. The user hasn't misunderstood the rule and hasn't fumbled the action; with the correct path known and available, they judge that following it costs more than deviating from it, and deliberately pick the deviation. This is the defining test for separating violation from mistake: someone making a mistake believes the deviant action is the correct one; someone committing a violation knows what's correct and simply isn't doing it this time. Whether a given deviation counts as a violation rather than a mistake depends not on the action itself but on what the person actually knew about the correct procedure before acting.

Studying it

Confirming that a deviation is a violation rather than a mistake requires verifying the person's knowledge of the correct procedure before the act — training records, a history of correctly performing the task, or an interview taken before rather than after the incident. Post-hoc questioning is easily contaminated: a person may claim "I always knew the right way" once the outcome turned out badly, or conversely excuse themselves with "I didn't understand it at the time" — neither statement can stand alone as evidence.

Where it stops holding

If the "rule" in question was never actually communicated to the user, or they never had the chance to learn and practice the correct procedure, the deviation isn't a violation — it belongs under mistake instead. A violation presupposes that the correct path was genuinely available and genuinely known; when that premise doesn't hold, behavior that looks like deliberate defiance is really just something the person was never properly told.

Applying it

When diagnosing a deviation, first verify whether the person had the knowledge and ability to act correctly beforehand. Once confirmed as a violation candidate, don't respond with tighter interface constraints or more explanatory copy — those target slips and mistakes, and do nothing for someone who already knows the right way and simply chose otherwise. What actually needs checking is the trade-off behind the deviation: is the rule realistically executable, is the deviation tacitly tolerated, is the organization inadvertently rewarding it. Verification: for a batch of cases already classified as violations, apply an intervention that touches the trade-off rather than the interface — for instance, making the cost of deviating visible — and see if the deviation rate drops with the interface unchanged; if it does, the diagnosis holds. If nothing changes, re-check whether the "knowing" premise actually held.

Related

• Same group: A10.01.1 Slip — correct intention, deviated execution · A10.01.2 Mistake — the intention rests on a wrong mental model · A10.01.4 Slips are fixed by interface constraints, mistakes by model correction — the remedies are not interchangeable · A10.01.5 Classification must precede any redesign · A10.01.6 Blaming "user carelessness" halts diagnosis · A10.01.7 The line between violation and mistake is whether the deviation was intentional
• Nearby: A10.13 Violations and non-compliance · A10.09 Human reliability and blame culture
• Search terms: violation · deliberate deviation · rule non-compliance