Why do we watch horror movies and gross-out comedies? What is the best way to persuade someone to quit smoking? Why are we more likely to buy an item if an attractive person has just touched it? Rachel Herz joins Kerri to talk about how these questions are all tied to the feeling of disgust.

Herz is a professor of psychiatry and human behavior at the Brown University Medical School and the author of "That's Disgusting: Unraveling the Mysteries of Repulsion."

How easily disgusted are you? Take this quiz to find out.