"According to psychologist Paul Slovic’s research about how the head and heart can influence how much people want to give to support a cause, your message is more compelling when you tell the story of one and stick to how a donor’s investment can help that one person, not many."
http://www.networkforgood.com/nonprofitblog/why-donors-want-to-help-one-person-but-not-every-person/
