The brain is an amazing device susceptible to impressions. For example, if I tell ten people I want a nice red wagon, at least one or two will want one too. If I say I want a cheeseburger then even more will want that. The human mind is open to suggestions, but it's also vulnerable to fear. If I say I'm scared of spiders others will recognize the weirdness of that insect and be scared of it too. If I constantly scream everyday everywhere on the TV and news that we're all gonna die of the flu then people will become terrified and do everything I tell them to.