I'm not seeing what about this isn't obvious. If you stimulate a crowd of people by firing a gun into the air they all react at the same time. If you stimulate

I'm not seeing what about this isn't obvious. If you stimulate a crowd of people by firing a gun into the air they all react at the same time. If you stimulate a group of people with a stimulus it's possible to ignore like a story only the ones not ignoring it will react.