Social pressure. Wanting to fit in with the herd. I have a good example of this. First understand that this child has been around snakes and other reptiles all of her life. She has never been bitten, scratched or anything else for that matter. She has helped with cleaning duty since she could carry a water bowl. She plays with snakes and barbies at the same time. It is quite funny to see barbie try to ride a ball python. Anyway, one day we are cleaning and my other daughter who's "job" it is to hold snakes while I clean let an animal loose which crawled across the floor and under my other daughter. So the daughter with the new visitor starts screaming like her hair is on fine. I asked her why she was screaming. She said because the snake was touching her. So i then said to her, you have know that snake since she was born and you have played with her many times, tell me why you really screamed. Final answer was because my friends scream at school when the see a lizard or bug. I have "fixed" the problem, but this is my belief on how this happens.