From the author's webpage http://www.hsperson.com/pages/hsp.htm
In her national bestseller, The Highly Sensitive Person: How to Thrive When the World Overwhelms You, author Elaine Aron defines a distinct personality trait that affects as many as one out of every five people. According to Dr. Aron's definition, the Highly Sensitive Person (HSP) has a sensitive nervous system, is aware of subtleties in his/her surroundings, and is more easily overwhelmed when in a highly stimulating environment. Additionally, she says, the success of The Highly Sensitive Person is cause for celebration: "We've done it ourselves. And not surprisingly, since we are 15 to 20 percent of the population - that's fifty million in the United States. Highly sensitive people are real, we exist, and we've proven it. That alone is something to celebrate."