@Emma Bezzle, so far, it's just the initial shock to simulate the moment the knife punctures. Most people will never be stabbed in real life, but it's good for agents to know when they are. Some people don't ever know how it feels, and it's too late to call out when you're out in the field.
Until I played one of the Carmen games from 1995 with Lynn Thigpen, and I found a note left behind from one of her agents, I didn't realize that Carmen pays her people too Lol