Andrew Bellenkes conducted research on this expectation and found that if people expect something to happen with a particular frequency.
They often miss it if it happens more or less than their expectation.
The video is about airport security personnel frequently miss dangerous weapons due to unlikely encounters everyday.
Security personnel are looking for common things such as lotion bottles, liquids but not bomb parts or guns.
People build a unconscious mental model of how often an event occurs.
When designing a product or application where people need to notice an event that rarely occurs.
Use a strong signal to get people's attention
Caption: : We all know what this signal mean! Pure Panic!!!