Abstract
Keywords - Instrumentation, security, choices, human reliability, stress
This paper presents a law which predicts the behavior of a human being faced to a choice, before an action, and under stressful conditions. This law has been discovered when analyzing the misbehavior of drivers experimenting an accident when trying to disconnect the cruise control of a car (new option for customers of M-class cars in western Europe). This rule is applicable for every user of an electronic device, being professional or not. When a professional is intensively trained, he can overpass the law but with a lack of reliability in his actions under stress. Designing secure and robust MMI will benefit of taking care of this law.