Seven BILLION dollars. That's not chump change, and it is what Americans spend on Halloween every year... decorations, costumes, candy, all of it. Sure, it's a party, but it's a party in part about scaring people. Why DO we like to scream, at least if it's followed by a good laugh? That's the domain of sociologist Dr. Margee Kerr , the rare academic who is considered a "scare specialist." She shares the findings of some of her research with us... and psychologist David Zald from Vanderbilt